ValueTracking.cpp revision 6de29f8d960505421d61c80cdb738e16720b6c0e
1173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner//===- ValueTracking.cpp - Walk computations to compute properties --------===// 2173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// 3173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// The LLVM Compiler Infrastructure 4173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// 5173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// This file is distributed under the University of Illinois Open Source 6173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// License. See LICENSE.TXT for details. 7173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// 8173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner//===----------------------------------------------------------------------===// 9173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// 10173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// This file contains routines that help analyze properties that chains of 11173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// computations have. 12173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// 13173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner//===----------------------------------------------------------------------===// 14173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 15173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner#include "llvm/Analysis/ValueTracking.h" 16173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner#include "llvm/Constants.h" 17173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner#include "llvm/Instructions.h" 180ff39b3feb10477c224138156941234f5fa46f58Evan Cheng#include "llvm/GlobalVariable.h" 19173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner#include "llvm/IntrinsicInst.h" 200582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling#include "llvm/Target/TargetData.h" 21173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner#include "llvm/Support/GetElementPtrTypeIterator.h" 22173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner#include "llvm/Support/MathExtras.h" 2332a9e7a2654c4aab2e617fbe53140492b3d38066Chris Lattner#include <cstring> 24173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattnerusing namespace llvm; 25173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 26173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// getOpcode - If this is an Instruction or a ConstantExpr, return the 27173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// opcode value. Otherwise return UserOp1. 28173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattnerstatic unsigned getOpcode(const Value *V) { 29173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (const Instruction *I = dyn_cast<Instruction>(V)) 30173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return I->getOpcode(); 31173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 32173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return CE->getOpcode(); 33173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Use UserOp1 to mean there's no opcode. 34173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return Instruction::UserOp1; 35173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner} 36173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 37173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 38173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// ComputeMaskedBits - Determine which of the bits specified in Mask are 39173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// known to be either zero or one and return them in the KnownZero/KnownOne 40173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// bit sets. This code only analyzes bits in Mask, in order to short-circuit 41173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// processing. 42173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// NOTE: we cannot consider 'undef' to be "IsZero" here. The problem is that 43173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// we cannot optimize based on the assumption that it is zero without changing 44173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// it to be an explicit zero. If we don't change it to zero, other code could 45173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// optimized based on the contradictory assumption that it is non-zero. 46173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// Because instcombine aggressively folds operations with undef args anyway, 47173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// this won't lose us code quality. 48173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattnervoid llvm::ComputeMaskedBits(Value *V, const APInt &Mask, 49173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt &KnownZero, APInt &KnownOne, 50173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TargetData *TD, unsigned Depth) { 519004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman const unsigned MaxDepth = 6; 52173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert(V && "No Value?"); 539004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman assert(Depth <= MaxDepth && "Limit Search Depth"); 5479abedb83a4dd7d3583c7ca6df8283079acc3ba5Chris Lattner unsigned BitWidth = Mask.getBitWidth(); 556de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman assert((V->getType()->isIntOrIntVector() || isa<PointerType>(V->getType())) && 56173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner "Not integer or pointer type!"); 576de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman assert((!TD || 586de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman TD->getTypeSizeInBits(V->getType()->getScalarType()) == BitWidth) && 596de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman (!V->getType()->isIntOrIntVector() || 606de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman V->getType()->getScalarSizeInBits() == BitWidth) && 61173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.getBitWidth() == BitWidth && 62173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.getBitWidth() == BitWidth && 63173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner "V, Mask, KnownOne and KnownZero should have same BitWidth"); 64173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 65173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 66173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // We know all of the bits for a constant! 67173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne = CI->getValue() & Mask; 68173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = ~KnownOne & Mask; 69173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 70173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 716de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman // Null and aggregate-zero are all-zeros. 726de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman if (isa<ConstantPointerNull>(V) || 736de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman isa<ConstantAggregateZero>(V)) { 74173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.clear(); 75173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = Mask; 76173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 77173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 786de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman // Handle a constant vector by taking the intersection of the known bits of 796de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman // each element. 806de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) { 816de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman KnownZero.set(); KnownOne.set(); 826de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) { 836de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman APInt KnownZero2(BitWidth, 0), KnownOne2(BitWidth, 0); 846de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman ComputeMaskedBits(CV->getOperand(i), Mask, KnownZero2, KnownOne2, 856de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman TD, Depth); 866de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman KnownZero &= KnownZero2; 876de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman KnownOne &= KnownOne2; 886de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman } 896de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman return; 906de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman } 91173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // The address of an aligned GlobalValue has trailing zeros. 92173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) { 93173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned Align = GV->getAlignment(); 94173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Align == 0 && TD && GV->getType()->getElementType()->isSized()) 95173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Align = TD->getPrefTypeAlignment(GV->getType()->getElementType()); 96173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Align > 0) 97173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = Mask & APInt::getLowBitsSet(BitWidth, 98173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner CountTrailingZeros_32(Align)); 99173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner else 100173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.clear(); 101173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.clear(); 102173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 103173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 104173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 105173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.clear(); KnownOne.clear(); // Start out not knowing anything. 106173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 1079004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman if (Depth == MaxDepth || Mask == 0) 108173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; // Limit search depth. 109173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 110173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner User *I = dyn_cast<User>(V); 111173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (!I) return; 112173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 113173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt KnownZero2(KnownZero), KnownOne2(KnownOne); 114173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner switch (getOpcode(I)) { 115173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner default: break; 116173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::And: { 117173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If either the LHS or the RHS are Zero, the result is zero. 118173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1); 119173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2(Mask & ~KnownZero); 120173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, 121173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 122173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 123173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); 124173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 125173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Output known-1 bits are only known if set in both the LHS & RHS. 126173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne &= KnownOne2; 127173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Output known-0 are known to be clear if zero in either the LHS | RHS. 128173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= KnownZero2; 129173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 130173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 131173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Or: { 132173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1); 133173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2(Mask & ~KnownOne); 134173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, 135173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 136173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 137173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); 138173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 139173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Output known-0 bits are only known if clear in both the LHS & RHS. 140173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero &= KnownZero2; 141173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Output known-1 are known to be set if set in either the LHS | RHS. 142173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne |= KnownOne2; 143173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 144173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 145173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Xor: { 146173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1); 147173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, TD, 148173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 149173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 150173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); 151173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 152173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Output known-0 bits are known if clear or set in both the LHS & RHS. 153173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt KnownZeroOut = (KnownZero & KnownZero2) | (KnownOne & KnownOne2); 154173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Output known-1 are known to be set if set in only one of the LHS, RHS. 155173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne = (KnownZero & KnownOne2) | (KnownOne & KnownZero2); 156173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = KnownZeroOut; 157173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 158173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 159173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Mul: { 160173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2 = APInt::getAllOnesValue(BitWidth); 161173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), Mask2, KnownZero, KnownOne, TD,Depth+1); 162173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, 163173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 164173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 165173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); 166173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 167173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If low bits are zero in either operand, output low known-0 bits. 168173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Also compute a conserative estimate for high known-0 bits. 169173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // More trickiness is possible, but this is sufficient for the 170173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // interesting case of alignment computation. 171173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.clear(); 172173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned TrailZ = KnownZero.countTrailingOnes() + 173173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero2.countTrailingOnes(); 174173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned LeadZ = std::max(KnownZero.countLeadingOnes() + 175173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero2.countLeadingOnes(), 176173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner BitWidth) - BitWidth; 177173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 178173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TrailZ = std::min(TrailZ, BitWidth); 179173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LeadZ = std::min(LeadZ, BitWidth); 180173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) | 181173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt::getHighBitsSet(BitWidth, LeadZ); 182173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero &= Mask; 183173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 184173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 185173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::UDiv: { 186173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // For the purposes of computing leading zeros we can conservatively 187173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // treat a udiv as a logical right shift by the power of 2 known to 188173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // be less than the denominator. 189173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt AllOnes = APInt::getAllOnesValue(BitWidth); 190173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), 191173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner AllOnes, KnownZero2, KnownOne2, TD, Depth+1); 192173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned LeadZ = KnownZero2.countLeadingOnes(); 193173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 194173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne2.clear(); 195173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero2.clear(); 196173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), 197173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner AllOnes, KnownZero2, KnownOne2, TD, Depth+1); 198173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned RHSUnknownLeadingOnes = KnownOne2.countLeadingZeros(); 199173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (RHSUnknownLeadingOnes != BitWidth) 200173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LeadZ = std::min(BitWidth, 201173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LeadZ + BitWidth - RHSUnknownLeadingOnes - 1); 202173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 203173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ) & Mask; 204173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 205173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 206173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Select: 207173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(2), Mask, KnownZero, KnownOne, TD, Depth+1); 208173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), Mask, KnownZero2, KnownOne2, TD, 209173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 210173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 211173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); 212173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 213173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Only known if known in both the LHS and RHS. 214173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne &= KnownOne2; 215173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero &= KnownZero2; 216173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 217173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::FPTrunc: 218173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::FPExt: 219173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::FPToUI: 220173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::FPToSI: 221173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::SIToFP: 222173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::UIToFP: 223173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; // Can't work with floating point. 224173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::PtrToInt: 225173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::IntToPtr: 226173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // We can't handle these if we don't know the pointer size. 227173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (!TD) return; 228173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // FALL THROUGH and handle them the same as zext/trunc. 229173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::ZExt: 230173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Trunc: { 231173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Note that we handle pointer operands here because of inttoptr/ptrtoint 232173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // which fall through here. 233173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner const Type *SrcTy = I->getOperand(0)->getType(); 23479abedb83a4dd7d3583c7ca6df8283079acc3ba5Chris Lattner unsigned SrcBitWidth = TD ? 235173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TD->getTypeSizeInBits(SrcTy) : 2366de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman SrcTy->getScalarSizeInBits(); 237173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt MaskIn(Mask); 238173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner MaskIn.zextOrTrunc(SrcBitWidth); 239173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.zextOrTrunc(SrcBitWidth); 240173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.zextOrTrunc(SrcBitWidth); 241173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, TD, 242173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 243173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.zextOrTrunc(BitWidth); 244173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.zextOrTrunc(BitWidth); 245173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Any top bits are known to be zero. 246173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (BitWidth > SrcBitWidth) 247173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth); 248173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 249173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 250173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::BitCast: { 251173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner const Type *SrcTy = I->getOperand(0)->getType(); 252173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (SrcTy->isInteger() || isa<PointerType>(SrcTy)) { 253173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, TD, 254173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 255173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 256173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 257173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 258173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 259173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::SExt: { 260173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Compute the bits in the result that are not present in the input. 261173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType()); 26279abedb83a4dd7d3583c7ca6df8283079acc3ba5Chris Lattner unsigned SrcBitWidth = SrcTy->getBitWidth(); 263173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 264173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt MaskIn(Mask); 265173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner MaskIn.trunc(SrcBitWidth); 266173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.trunc(SrcBitWidth); 267173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.trunc(SrcBitWidth); 268173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, TD, 269173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 270173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 271173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.zext(BitWidth); 272173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.zext(BitWidth); 273173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 274173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If the sign bit of the input is known set or clear, then we know the 275173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // top bits of the result. 276173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (KnownZero[SrcBitWidth-1]) // Input sign bit known zero 277173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth); 278173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner else if (KnownOne[SrcBitWidth-1]) // Input sign bit known set 279173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth); 280173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 281173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 282173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Shl: 283173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0 284173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { 285173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner uint64_t ShiftAmt = SA->getLimitedValue(BitWidth); 286173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2(Mask.lshr(ShiftAmt)); 287173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD, 288173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 289173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 290173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero <<= ShiftAmt; 291173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne <<= ShiftAmt; 292173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= APInt::getLowBitsSet(BitWidth, ShiftAmt); // low bits known 0 293173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 294173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 295173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 296173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::LShr: 297173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0 298173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { 299173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Compute the new bits that are at the top now. 300173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner uint64_t ShiftAmt = SA->getLimitedValue(BitWidth); 301173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 302173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Unsigned shift right. 303173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2(Mask.shl(ShiftAmt)); 304173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero,KnownOne, TD, 305173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 306173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?"); 307173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APIntOps::lshr(KnownZero, ShiftAmt); 308173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne = APIntOps::lshr(KnownOne, ShiftAmt); 309173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // high bits known zero. 310173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= APInt::getHighBitsSet(BitWidth, ShiftAmt); 311173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 312173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 313173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 314173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::AShr: 315173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // (ashr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0 316173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { 317173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Compute the new bits that are at the top now. 318173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner uint64_t ShiftAmt = SA->getLimitedValue(BitWidth); 319173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 320173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Signed shift right. 321173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2(Mask.shl(ShiftAmt)); 322173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD, 323173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 324173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?"); 325173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APIntOps::lshr(KnownZero, ShiftAmt); 326173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne = APIntOps::lshr(KnownOne, ShiftAmt); 327173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 328173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt)); 329173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (KnownZero[BitWidth-ShiftAmt-1]) // New bits are known zero. 330173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= HighBits; 331173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner else if (KnownOne[BitWidth-ShiftAmt-1]) // New bits are known one. 332173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne |= HighBits; 333173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 334173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 335173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 336173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Sub: { 337173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *CLHS = dyn_cast<ConstantInt>(I->getOperand(0))) { 338173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // We know that the top bits of C-X are clear if X contains less bits 339173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // than C (i.e. no wrap-around can happen). For example, 20-X is 340173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // positive if we can prove that X is >= 0 and < 16. 341173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (!CLHS->getValue().isNegative()) { 342173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned NLZ = (CLHS->getValue()+1).countLeadingZeros(); 343173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // NLZ can't be BitWidth with no sign bit 344173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt MaskV = APInt::getHighBitsSet(BitWidth, NLZ+1); 345173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), MaskV, KnownZero2, KnownOne2, 346173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TD, Depth+1); 347173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 348173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If all of the MaskV bits are known to be zero, then we know the 349173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // output top bits are zero, because we now know that the output is 350173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // from [0-C]. 351173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if ((KnownZero2 & MaskV) == MaskV) { 352173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned NLZ2 = CLHS->getValue().countLeadingZeros(); 353173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Top bits known zero. 354173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APInt::getHighBitsSet(BitWidth, NLZ2) & Mask; 355173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 356173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 357173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 358173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 359173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // fall through 360173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Add: { 3613925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // If one of the operands has trailing zeros, than the bits that the 3623925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // other operand has in those bit positions will be preserved in the 3633925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // result. For an add, this works with either operand. For a subtract, 3643925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // this only works if the known zeros are in the right operand. 3653925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0); 3663925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman APInt Mask2 = APInt::getLowBitsSet(BitWidth, 3673925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman BitWidth - Mask.countLeadingZeros()); 3683925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman ComputeMaskedBits(I->getOperand(0), Mask2, LHSKnownZero, LHSKnownOne, TD, 369173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 3703925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman assert((LHSKnownZero & LHSKnownOne) == 0 && 3713925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman "Bits known to be one AND zero?"); 3723925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman unsigned LHSKnownZeroOut = LHSKnownZero.countTrailingOnes(); 373173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 374173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), Mask2, KnownZero2, KnownOne2, TD, 375173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 376173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); 3773925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman unsigned RHSKnownZeroOut = KnownZero2.countTrailingOnes(); 378173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 3793925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // Determine which operand has more trailing zeros, and use that 3803925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // many bits from the other operand. 3813925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman if (LHSKnownZeroOut > RHSKnownZeroOut) { 3823925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman if (getOpcode(I) == Instruction::Add) { 3833925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman APInt Mask = APInt::getLowBitsSet(BitWidth, LHSKnownZeroOut); 3843925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman KnownZero |= KnownZero2 & Mask; 3853925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman KnownOne |= KnownOne2 & Mask; 3863925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman } else { 3873925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // If the known zeros are in the left operand for a subtract, 3883925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // fall back to the minimum known zeros in both operands. 3893925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman KnownZero |= APInt::getLowBitsSet(BitWidth, 3903925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman std::min(LHSKnownZeroOut, 3913925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman RHSKnownZeroOut)); 3923925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman } 3933925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman } else if (RHSKnownZeroOut >= LHSKnownZeroOut) { 3943925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman APInt Mask = APInt::getLowBitsSet(BitWidth, RHSKnownZeroOut); 3953925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman KnownZero |= LHSKnownZero & Mask; 3963925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman KnownOne |= LHSKnownOne & Mask; 3973925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman } 398173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 399173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 400173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::SRem: 401173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) { 402173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt RA = Rem->getValue(); 403173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (RA.isPowerOf2() || (-RA).isPowerOf2()) { 404173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt LowBits = RA.isStrictlyPositive() ? (RA - 1) : ~RA; 405173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2 = LowBits | APInt::getSignBit(BitWidth); 406173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, 407173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 408173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 409a60832b0187642d01fd726dc766cd62587f6add0Dan Gohman // If the sign bit of the first operand is zero, the sign bit of 410a60832b0187642d01fd726dc766cd62587f6add0Dan Gohman // the result is zero. If the first operand has no one bits below 411a60832b0187642d01fd726dc766cd62587f6add0Dan Gohman // the second operand's single 1 bit, its sign will be zero. 412173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (KnownZero2[BitWidth-1] || ((KnownZero2 & LowBits) == LowBits)) 413173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero2 |= ~LowBits; 414173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 415173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= KnownZero2 & Mask; 416173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 417173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?"); 418173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 419173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 420173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 421173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::URem: { 422173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) { 423173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt RA = Rem->getValue(); 424173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (RA.isPowerOf2()) { 425173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt LowBits = (RA - 1); 426173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2 = LowBits & Mask; 427173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= ~LowBits & Mask; 428173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD, 429173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 430173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?"); 431173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 432173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 433173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 434173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 435173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Since the result is less than or equal to either operand, any leading 436173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // zero bits in either operand must also exist in the result. 437173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt AllOnes = APInt::getAllOnesValue(BitWidth); 438173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), AllOnes, KnownZero, KnownOne, 439173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TD, Depth+1); 440173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), AllOnes, KnownZero2, KnownOne2, 441173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TD, Depth+1); 442173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 44379abedb83a4dd7d3583c7ca6df8283079acc3ba5Chris Lattner unsigned Leaders = std::max(KnownZero.countLeadingOnes(), 444173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero2.countLeadingOnes()); 445173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.clear(); 446173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APInt::getHighBitsSet(BitWidth, Leaders) & Mask; 447173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 448173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 449173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 450173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Alloca: 451173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Malloc: { 452173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner AllocationInst *AI = cast<AllocationInst>(V); 453173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned Align = AI->getAlignment(); 454173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Align == 0 && TD) { 455173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (isa<AllocaInst>(AI)) 4560f2831c820151aa6f2cd6a8bd7b6b633b1035524Chris Lattner Align = TD->getABITypeAlignment(AI->getType()->getElementType()); 457173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner else if (isa<MallocInst>(AI)) { 458173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Malloc returns maximally aligned memory. 459173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Align = TD->getABITypeAlignment(AI->getType()->getElementType()); 460173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Align = 461173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner std::max(Align, 462173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner (unsigned)TD->getABITypeAlignment(Type::DoubleTy)); 463173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Align = 464173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner std::max(Align, 465173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner (unsigned)TD->getABITypeAlignment(Type::Int64Ty)); 466173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 467173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 468173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 469173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Align > 0) 470173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = Mask & APInt::getLowBitsSet(BitWidth, 471173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner CountTrailingZeros_32(Align)); 472173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 473173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 474173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::GetElementPtr: { 475173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Analyze all of the subscripts of this getelementptr instruction 476173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // to determine if we can prove known low zero bits. 477173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt LocalMask = APInt::getAllOnesValue(BitWidth); 478173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt LocalKnownZero(BitWidth, 0), LocalKnownOne(BitWidth, 0); 479173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), LocalMask, 480173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LocalKnownZero, LocalKnownOne, TD, Depth+1); 481173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned TrailZ = LocalKnownZero.countTrailingOnes(); 482173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 483173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner gep_type_iterator GTI = gep_type_begin(I); 484173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i, ++GTI) { 485173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Value *Index = I->getOperand(i); 486173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (const StructType *STy = dyn_cast<StructType>(*GTI)) { 487173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Handle struct member offset arithmetic. 488173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (!TD) return; 489173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner const StructLayout *SL = TD->getStructLayout(STy); 490173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned Idx = cast<ConstantInt>(Index)->getZExtValue(); 491173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner uint64_t Offset = SL->getElementOffset(Idx); 492173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TrailZ = std::min(TrailZ, 493173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner CountTrailingZeros_64(Offset)); 494173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } else { 495173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Handle array index arithmetic. 496173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner const Type *IndexedTy = GTI.getIndexedType(); 497173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (!IndexedTy->isSized()) return; 4986de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman unsigned GEPOpiBits = Index->getType()->getScalarSizeInBits(); 499777d2306b36816a53bc1ae1244c0dc7d998ae691Duncan Sands uint64_t TypeSize = TD ? TD->getTypeAllocSize(IndexedTy) : 1; 500173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LocalMask = APInt::getAllOnesValue(GEPOpiBits); 501173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LocalKnownZero = LocalKnownOne = APInt(GEPOpiBits, 0); 502173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(Index, LocalMask, 503173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LocalKnownZero, LocalKnownOne, TD, Depth+1); 504173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TrailZ = std::min(TrailZ, 50579abedb83a4dd7d3583c7ca6df8283079acc3ba5Chris Lattner unsigned(CountTrailingZeros_64(TypeSize) + 50679abedb83a4dd7d3583c7ca6df8283079acc3ba5Chris Lattner LocalKnownZero.countTrailingOnes())); 507173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 508173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 509173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 510173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) & Mask; 511173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 512173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 513173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::PHI: { 514173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner PHINode *P = cast<PHINode>(I); 515173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Handle the case of a simple two-predecessor recurrence PHI. 516173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // There's a lot more that could theoretically be done here, but 517173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // this is sufficient to catch some interesting cases. 518173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (P->getNumIncomingValues() == 2) { 519173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner for (unsigned i = 0; i != 2; ++i) { 520173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Value *L = P->getIncomingValue(i); 521173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Value *R = P->getIncomingValue(!i); 522173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner User *LU = dyn_cast<User>(L); 523173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (!LU) 524173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner continue; 525173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned Opcode = getOpcode(LU); 526173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Check for operations that have the property that if 527173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // both their operands have low zero bits, the result 528173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // will have low zero bits. 529173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Opcode == Instruction::Add || 530173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Opcode == Instruction::Sub || 531173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Opcode == Instruction::And || 532173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Opcode == Instruction::Or || 533173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Opcode == Instruction::Mul) { 534173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Value *LL = LU->getOperand(0); 535173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Value *LR = LU->getOperand(1); 536173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Find a recurrence. 537173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (LL == I) 538173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner L = LR; 539173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner else if (LR == I) 540173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner L = LL; 541173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner else 542173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 543173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Ok, we have a PHI of the form L op= R. Check for low 544173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // zero bits. 545173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2 = APInt::getAllOnesValue(BitWidth); 546173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(R, Mask2, KnownZero2, KnownOne2, TD, Depth+1); 547173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Mask2 = APInt::getLowBitsSet(BitWidth, 548173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero2.countTrailingOnes()); 549c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene 550c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene // We need to take the minimum number of known bits 551c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene APInt KnownZero3(KnownZero), KnownOne3(KnownOne); 552c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene ComputeMaskedBits(L, Mask2, KnownZero3, KnownOne3, TD, Depth+1); 553c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene 554173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = Mask & 555173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt::getLowBitsSet(BitWidth, 556c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene std::min(KnownZero2.countTrailingOnes(), 557c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene KnownZero3.countTrailingOnes())); 558173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 559173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 560173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 561173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 5629004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman 5639004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // Otherwise take the unions of the known bit sets of the operands, 5649004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // taking conservative care to avoid excessive recursion. 5659004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman if (Depth < MaxDepth - 1 && !KnownZero && !KnownOne) { 5669004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownZero = APInt::getAllOnesValue(BitWidth); 5679004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownOne = APInt::getAllOnesValue(BitWidth); 5689004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i) { 5699004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // Skip direct self references. 5709004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman if (P->getIncomingValue(i) == P) continue; 5719004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman 5729004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownZero2 = APInt(BitWidth, 0); 5739004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownOne2 = APInt(BitWidth, 0); 5749004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // Recurse, but cap the recursion to one level, because we don't 5759004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // want to waste time spinning around in loops. 5769004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman ComputeMaskedBits(P->getIncomingValue(i), KnownZero | KnownOne, 5779004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownZero2, KnownOne2, TD, MaxDepth-1); 5789004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownZero &= KnownZero2; 5799004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownOne &= KnownOne2; 5809004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // If all bits have been ruled out, there's no need to check 5819004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // more operands. 5829004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman if (!KnownZero && !KnownOne) 5839004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman break; 5849004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman } 5859004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman } 586173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 587173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 588173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Call: 589173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { 590173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner switch (II->getIntrinsicID()) { 591173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner default: break; 592173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Intrinsic::ctpop: 593173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Intrinsic::ctlz: 594173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Intrinsic::cttz: { 595173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned LowBits = Log2_32(BitWidth)+1; 596173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - LowBits); 597173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 598173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 599173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 600173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 601173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 602173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 603173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner} 604173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 605173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use 606173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// this predicate to simplify operations downstream. Mask is known to be zero 607173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// for bits that V cannot have. 608173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattnerbool llvm::MaskedValueIsZero(Value *V, const APInt &Mask, 609173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TargetData *TD, unsigned Depth) { 610173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt KnownZero(Mask.getBitWidth(), 0), KnownOne(Mask.getBitWidth(), 0); 611173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD, Depth); 612173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 613173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return (KnownZero & Mask) == Mask; 614173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner} 615173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 616173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 617173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 618173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// ComputeNumSignBits - Return the number of times the sign bit of the 619173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// register is replicated into the other bits. We know that at least 1 bit 620173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// is always equal to the sign bit (itself), but other cases can give us 621173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// information. For example, immediately after an "ashr X, 2", we know that 622173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// the top 3 bits are all equal to each other, so we return 3. 623173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// 624173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// 'Op' must have a scalar integer type. 625173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// 626173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattnerunsigned llvm::ComputeNumSignBits(Value *V, TargetData *TD, unsigned Depth) { 6276de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman const Type *Ty = V->getType(); 6286de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman unsigned TyBits = Ty->getScalarSizeInBits(); 629173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned Tmp, Tmp2; 630173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned FirstAnswer = 1; 631173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 632d82e511aec0ea27ddd4c1e504b37f689796e965fChris Lattner // Note that ConstantInt is handled by the general ComputeMaskedBits case 633d82e511aec0ea27ddd4c1e504b37f689796e965fChris Lattner // below. 634d82e511aec0ea27ddd4c1e504b37f689796e965fChris Lattner 635173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Depth == 6) 636173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return 1; // Limit search depth. 637173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 638173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner User *U = dyn_cast<User>(V); 639173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner switch (getOpcode(V)) { 640173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner default: break; 641173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::SExt: 642173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = TyBits-cast<IntegerType>(U->getOperand(0)->getType())->getBitWidth(); 643173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return ComputeNumSignBits(U->getOperand(0), TD, Depth+1) + Tmp; 644173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 645173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::AShr: 646173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1); 647173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // ashr X, C -> adds C sign bits. 648173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *C = dyn_cast<ConstantInt>(U->getOperand(1))) { 649173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp += C->getZExtValue(); 650173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp > TyBits) Tmp = TyBits; 651173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 652173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return Tmp; 653173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Shl: 654173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *C = dyn_cast<ConstantInt>(U->getOperand(1))) { 655173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // shl destroys sign bits. 656173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1); 657173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (C->getZExtValue() >= TyBits || // Bad shift. 658173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner C->getZExtValue() >= Tmp) break; // Shifted all sign bits out. 659173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return Tmp - C->getZExtValue(); 660173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 661173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 662173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::And: 663173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Or: 664173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Xor: // NOT is handled here. 665173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Logical binary ops preserve the number of sign bits at the worst. 666173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1); 667173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp != 1) { 668173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp2 = ComputeNumSignBits(U->getOperand(1), TD, Depth+1); 669173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner FirstAnswer = std::min(Tmp, Tmp2); 670173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // We computed what we know about the sign bits as our first 671173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // answer. Now proceed to the generic code that uses 672173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // ComputeMaskedBits, and pick whichever answer is better. 673173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 674173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 675173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 676173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Select: 677173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = ComputeNumSignBits(U->getOperand(1), TD, Depth+1); 678173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp == 1) return 1; // Early out. 679173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp2 = ComputeNumSignBits(U->getOperand(2), TD, Depth+1); 680173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return std::min(Tmp, Tmp2); 681173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 682173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Add: 683173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Add can have at most one carry bit. Thus we know that the output 684173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // is, at worst, one more bit than the inputs. 685173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1); 686173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp == 1) return 1; // Early out. 687173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 688173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Special case decrementing a value (ADD X, -1): 6890001e56f15215ae4bc5fffb82eec5c4828b888f0Dan Gohman if (ConstantInt *CRHS = dyn_cast<ConstantInt>(U->getOperand(1))) 690173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (CRHS->isAllOnesValue()) { 691173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0); 692173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask = APInt::getAllOnesValue(TyBits); 693173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(U->getOperand(0), Mask, KnownZero, KnownOne, TD, 694173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 695173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 696173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If the input is known to be 0 or 1, the output is 0/-1, which is all 697173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // sign bits set. 698173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if ((KnownZero | APInt(TyBits, 1)) == Mask) 699173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return TyBits; 700173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 701173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If we are subtracting one from a positive number, there is no carry 702173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // out of the result. 703173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (KnownZero.isNegative()) 704173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return Tmp; 705173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 706173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 707173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp2 = ComputeNumSignBits(U->getOperand(1), TD, Depth+1); 708173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp2 == 1) return 1; 709173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return std::min(Tmp, Tmp2)-1; 710173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 711173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 712173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Sub: 713173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp2 = ComputeNumSignBits(U->getOperand(1), TD, Depth+1); 714173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp2 == 1) return 1; 715173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 716173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Handle NEG. 717173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *CLHS = dyn_cast<ConstantInt>(U->getOperand(0))) 718173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (CLHS->isNullValue()) { 719173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0); 720173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask = APInt::getAllOnesValue(TyBits); 721173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(U->getOperand(1), Mask, KnownZero, KnownOne, 722173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TD, Depth+1); 723173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If the input is known to be 0 or 1, the output is 0/-1, which is all 724173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // sign bits set. 725173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if ((KnownZero | APInt(TyBits, 1)) == Mask) 726173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return TyBits; 727173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 728173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If the input is known to be positive (the sign bit is known clear), 729173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // the output of the NEG has the same number of sign bits as the input. 730173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (KnownZero.isNegative()) 731173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return Tmp2; 732173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 733173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Otherwise, we treat this like a SUB. 734173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 735173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 736173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Sub can have at most one carry bit. Thus we know that the output 737173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // is, at worst, one more bit than the inputs. 738173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1); 739173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp == 1) return 1; // Early out. 740173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return std::min(Tmp, Tmp2)-1; 741173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 742173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Trunc: 743173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // FIXME: it's tricky to do anything useful for this, but it is an important 744173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // case for targets like X86. 745173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 746173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 747173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 748173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Finally, if we can prove that the top bits of the result are 0's or 1's, 749173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // use this information. 750173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0); 751173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask = APInt::getAllOnesValue(TyBits); 752173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD, Depth); 753173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 754173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (KnownZero.isNegative()) { // sign bit is 0 755173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Mask = KnownZero; 756173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } else if (KnownOne.isNegative()) { // sign bit is 1; 757173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Mask = KnownOne; 758173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } else { 759173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Nothing known. 760173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return FirstAnswer; 761173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 762173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 763173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Okay, we know that the sign bit in Mask is set. Use CLZ to determine 764173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // the number of identical bits in the top of the input value. 765173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Mask = ~Mask; 766173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Mask <<= Mask.getBitWidth()-TyBits; 767173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Return # leading zeros. We use 'min' here in case Val was zero before 768173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // shifting. We don't want to return '64' as for an i32 "0". 769173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return std::max(FirstAnswer, std::min(TyBits, Mask.countLeadingZeros())); 770173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner} 771833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 772833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner/// CannotBeNegativeZero - Return true if we can prove that the specified FP 773833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner/// value is never equal to -0.0. 774833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner/// 775833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner/// NOTE: this function will need to be revisited when we support non-default 776833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner/// rounding modes! 777833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner/// 778833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattnerbool llvm::CannotBeNegativeZero(const Value *V, unsigned Depth) { 779833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (const ConstantFP *CFP = dyn_cast<ConstantFP>(V)) 780833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner return !CFP->getValueAPF().isNegZero(); 781833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 782833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (Depth == 6) 783833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner return 1; // Limit search depth. 784833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 785833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner const Instruction *I = dyn_cast<Instruction>(V); 786833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (I == 0) return false; 787833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 788833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner // (add x, 0.0) is guaranteed to return +0.0, not -0.0. 789ae3a0be92e33bc716722aa600983fc1535acb122Dan Gohman if (I->getOpcode() == Instruction::FAdd && 790833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner isa<ConstantFP>(I->getOperand(1)) && 791833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner cast<ConstantFP>(I->getOperand(1))->isNullValue()) 792833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner return true; 793833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 794833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner // sitofp and uitofp turn into +0.0 for zero. 795833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (isa<SIToFPInst>(I) || isa<UIToFPInst>(I)) 796833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner return true; 797833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 798833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) 799833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner // sqrt(-0.0) = -0.0, no other negative results are possible. 800833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (II->getIntrinsicID() == Intrinsic::sqrt) 801833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner return CannotBeNegativeZero(II->getOperand(1), Depth+1); 802833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 803833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (const CallInst *CI = dyn_cast<CallInst>(I)) 804833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (const Function *F = CI->getCalledFunction()) { 805833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (F->isDeclaration()) { 806833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner switch (F->getNameLen()) { 807833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner case 3: // abs(x) != -0.0 808833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (!strcmp(F->getNameStart(), "abs")) return true; 809833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner break; 810833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner case 4: // abs[lf](x) != -0.0 811833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (!strcmp(F->getNameStart(), "absf")) return true; 812833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (!strcmp(F->getNameStart(), "absl")) return true; 813833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner break; 814833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner } 815833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner } 816833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner } 817833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 818833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner return false; 819833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner} 820833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 821b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// This is the recursive version of BuildSubAggregate. It takes a few different 822b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// arguments. Idxs is the index within the nested struct From that we are 823b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// looking at now (which is of type IndexedType). IdxSkip is the number of 824b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// indices from Idxs that should be left out when inserting into the resulting 825b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// struct. To is the result struct built so far, new insertvalue instructions 826b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// build on that. 827b23d5adbc8230167e711070b9298985de4580f30Matthijs KooijmanValue *BuildSubAggregate(Value *From, Value* To, const Type *IndexedType, 828b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman SmallVector<unsigned, 10> &Idxs, 829b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman unsigned IdxSkip, 8300a7413dad84887bee51f20d7a5f1c4c1c7bb4c1eMatthijs Kooijman Instruction *InsertBefore) { 831b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman const llvm::StructType *STy = llvm::dyn_cast<llvm::StructType>(IndexedType); 832b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman if (STy) { 8330a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // Save the original To argument so we can modify it 8340a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman Value *OrigTo = To; 835b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // General case, the type indexed by Idxs is a struct 836b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 837b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Process each struct element recursively 838b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman Idxs.push_back(i); 8390a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman Value *PrevTo = To; 840710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman To = BuildSubAggregate(From, To, STy->getElementType(i), Idxs, IdxSkip, 841710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman InsertBefore); 842b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman Idxs.pop_back(); 8430a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman if (!To) { 8440a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // Couldn't find any inserted value for this index? Cleanup 8450a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman while (PrevTo != OrigTo) { 8460a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman InsertValueInst* Del = cast<InsertValueInst>(PrevTo); 8470a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman PrevTo = Del->getAggregateOperand(); 8480a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman Del->eraseFromParent(); 8490a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman } 8500a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // Stop processing elements 8510a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman break; 8520a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman } 853b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman } 8540a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // If we succesfully found a value for each of our subaggregates 8550a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman if (To) 8560a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman return To; 857b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman } 8580a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // Base case, the type indexed by SourceIdxs is not a struct, or not all of 8590a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // the struct's elements had a value that was inserted directly. In the latter 8600a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // case, perhaps we can't determine each of the subelements individually, but 8610a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // we might be able to find the complete struct somewhere. 8620a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman 8630a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // Find the value that is at that particular spot 8640a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman Value *V = FindInsertedValue(From, Idxs.begin(), Idxs.end()); 8650a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman 8660a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman if (!V) 8670a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman return NULL; 8680a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman 8690a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // Insert the value in the new (sub) aggregrate 8700a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman return llvm::InsertValueInst::Create(To, V, Idxs.begin() + IdxSkip, 8710a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman Idxs.end(), "tmp", InsertBefore); 872b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman} 873b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 874b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// This helper takes a nested struct and extracts a part of it (which is again a 875b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// struct) into a new value. For example, given the struct: 876b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// { a, { b, { c, d }, e } } 877b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// and the indices "1, 1" this returns 878b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// { c, d }. 879b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// 8800a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman// It does this by inserting an insertvalue for each element in the resulting 8810a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman// struct, as opposed to just inserting a single struct. This will only work if 8820a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman// each of the elements of the substruct are known (ie, inserted into From by an 8830a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman// insertvalue instruction somewhere). 884b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// 8850a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman// All inserted insertvalue instructions are inserted before InsertBefore 886710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs KooijmanValue *BuildSubAggregate(Value *From, const unsigned *idx_begin, 8870a7413dad84887bee51f20d7a5f1c4c1c7bb4c1eMatthijs Kooijman const unsigned *idx_end, Instruction *InsertBefore) { 888977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman assert(InsertBefore && "Must have someplace to insert!"); 889710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman const Type *IndexedType = ExtractValueInst::getIndexedType(From->getType(), 890710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman idx_begin, 891710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman idx_end); 892b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman Value *To = UndefValue::get(IndexedType); 893b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman SmallVector<unsigned, 10> Idxs(idx_begin, idx_end); 894b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman unsigned IdxSkip = Idxs.size(); 895b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 896b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman return BuildSubAggregate(From, To, IndexedType, Idxs, IdxSkip, InsertBefore); 897b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman} 898b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 899710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman/// FindInsertedValue - Given an aggregrate and an sequence of indices, see if 900710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman/// the scalar value indexed is already around as a register, for example if it 901710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman/// were inserted directly into the aggregrate. 9020a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman/// 9030a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman/// If InsertBefore is not null, this function will duplicate (modified) 9040a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman/// insertvalues when a part of a nested struct is extracted. 905b23d5adbc8230167e711070b9298985de4580f30Matthijs KooijmanValue *llvm::FindInsertedValue(Value *V, const unsigned *idx_begin, 9060a7413dad84887bee51f20d7a5f1c4c1c7bb4c1eMatthijs Kooijman const unsigned *idx_end, Instruction *InsertBefore) { 907b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Nothing to index? Just return V then (this is useful at the end of our 908b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // recursion) 909b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman if (idx_begin == idx_end) 910b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman return V; 911b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // We have indices, so V should have an indexable type 912b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman assert((isa<StructType>(V->getType()) || isa<ArrayType>(V->getType())) 913b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman && "Not looking at a struct or array?"); 914b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman assert(ExtractValueInst::getIndexedType(V->getType(), idx_begin, idx_end) 915b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman && "Invalid indices for type?"); 916b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman const CompositeType *PTy = cast<CompositeType>(V->getType()); 917b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 918b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman if (isa<UndefValue>(V)) 919b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman return UndefValue::get(ExtractValueInst::getIndexedType(PTy, 920b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman idx_begin, 921b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman idx_end)); 922b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman else if (isa<ConstantAggregateZero>(V)) 923b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman return Constant::getNullValue(ExtractValueInst::getIndexedType(PTy, 924b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman idx_begin, 925b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman idx_end)); 926b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman else if (Constant *C = dyn_cast<Constant>(V)) { 927b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman if (isa<ConstantArray>(C) || isa<ConstantStruct>(C)) 928b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Recursively process this constant 929dddc827125d307d8e992339d00ce4a6e3fe21e73Matthijs Kooijman return FindInsertedValue(C->getOperand(*idx_begin), idx_begin + 1, idx_end, 930710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman InsertBefore); 931b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman } else if (InsertValueInst *I = dyn_cast<InsertValueInst>(V)) { 932b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Loop the indices for the insertvalue instruction in parallel with the 933b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // requested indices 934b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman const unsigned *req_idx = idx_begin; 935710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman for (const unsigned *i = I->idx_begin(), *e = I->idx_end(); 936710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman i != e; ++i, ++req_idx) { 9379954c76f2c89ab3c70bfe8222534621a86f9085aDuncan Sands if (req_idx == idx_end) { 938977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman if (InsertBefore) 9390a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // The requested index identifies a part of a nested aggregate. Handle 9400a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // this specially. For example, 9410a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // %A = insertvalue { i32, {i32, i32 } } undef, i32 10, 1, 0 9420a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // %B = insertvalue { i32, {i32, i32 } } %A, i32 11, 1, 1 9430a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // %C = extractvalue {i32, { i32, i32 } } %B, 1 9440a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // This can be changed into 9450a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // %A = insertvalue {i32, i32 } undef, i32 10, 0 9460a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // %C = insertvalue {i32, i32 } %A, i32 11, 1 9470a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // which allows the unused 0,0 element from the nested struct to be 9480a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // removed. 949977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman return BuildSubAggregate(V, idx_begin, req_idx, InsertBefore); 950977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman else 951977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman // We can't handle this without inserting insertvalues 952977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman return 0; 9539954c76f2c89ab3c70bfe8222534621a86f9085aDuncan Sands } 954b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 955b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // This insert value inserts something else than what we are looking for. 956b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // See if the (aggregrate) value inserted into has the value we are 957b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // looking for, then. 958b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman if (*req_idx != *i) 959710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman return FindInsertedValue(I->getAggregateOperand(), idx_begin, idx_end, 960710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman InsertBefore); 961b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman } 962b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // If we end up here, the indices of the insertvalue match with those 963b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // requested (though possibly only partially). Now we recursively look at 964b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // the inserted value, passing any remaining indices. 965710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman return FindInsertedValue(I->getInsertedValueOperand(), req_idx, idx_end, 966710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman InsertBefore); 967b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman } else if (ExtractValueInst *I = dyn_cast<ExtractValueInst>(V)) { 968b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // If we're extracting a value from an aggregrate that was extracted from 969b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // something else, we can extract from that something else directly instead. 970b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // However, we will need to chain I's indices with the requested indices. 971b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 972b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Calculate the number of indices required 973b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman unsigned size = I->getNumIndices() + (idx_end - idx_begin); 974b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Allocate some space to put the new indices in 9753faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman SmallVector<unsigned, 5> Idxs; 9763faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman Idxs.reserve(size); 977b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Add indices from the extract value instruction 978710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman for (const unsigned *i = I->idx_begin(), *e = I->idx_end(); 9793faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman i != e; ++i) 9803faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman Idxs.push_back(*i); 981b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 982b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Add requested indices 9833faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman for (const unsigned *i = idx_begin, *e = idx_end; i != e; ++i) 9843faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman Idxs.push_back(*i); 985b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 9863faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman assert(Idxs.size() == size 987710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman && "Number of indices added not correct?"); 988b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 9893faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman return FindInsertedValue(I->getAggregateOperand(), Idxs.begin(), Idxs.end(), 990710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman InsertBefore); 991b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman } 992b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Otherwise, we don't know (such as, extracting from a function return value 993b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // or load instruction) 994b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman return 0; 995b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman} 9960ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 9970ff39b3feb10477c224138156941234f5fa46f58Evan Cheng/// GetConstantStringInfo - This function computes the length of a 9980ff39b3feb10477c224138156941234f5fa46f58Evan Cheng/// null-terminated C string pointed to by V. If successful, it returns true 9990ff39b3feb10477c224138156941234f5fa46f58Evan Cheng/// and returns the string in Str. If unsuccessful, it returns false. 10000582ae99ba75a556d6ff63b254da327d32ba036fBill Wendlingbool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset, 10010582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling bool StopAtNul) { 10020582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling // If V is NULL then return false; 10030582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (V == NULL) return false; 10040ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10050ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Look through bitcast instructions. 10060ff39b3feb10477c224138156941234f5fa46f58Evan Cheng if (BitCastInst *BCI = dyn_cast<BitCastInst>(V)) 10070582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return GetConstantStringInfo(BCI->getOperand(0), Str, Offset, StopAtNul); 10080582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling 10090ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // If the value is not a GEP instruction nor a constant expression with a 10100ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // GEP instruction, then return false because ConstantArray can't occur 10110ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // any other way 10120ff39b3feb10477c224138156941234f5fa46f58Evan Cheng User *GEP = 0; 10130ff39b3feb10477c224138156941234f5fa46f58Evan Cheng if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(V)) { 10140ff39b3feb10477c224138156941234f5fa46f58Evan Cheng GEP = GEPI; 10150ff39b3feb10477c224138156941234f5fa46f58Evan Cheng } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 10160ff39b3feb10477c224138156941234f5fa46f58Evan Cheng if (CE->getOpcode() == Instruction::BitCast) 10170582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return GetConstantStringInfo(CE->getOperand(0), Str, Offset, StopAtNul); 10180582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (CE->getOpcode() != Instruction::GetElementPtr) 10190582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10200ff39b3feb10477c224138156941234f5fa46f58Evan Cheng GEP = CE; 10210ff39b3feb10477c224138156941234f5fa46f58Evan Cheng } 10220ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10230ff39b3feb10477c224138156941234f5fa46f58Evan Cheng if (GEP) { 10240ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Make sure the GEP has exactly three arguments. 10250582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (GEP->getNumOperands() != 3) 10260582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10270582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling 10280ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Make sure the index-ee is a pointer to array of i8. 10290ff39b3feb10477c224138156941234f5fa46f58Evan Cheng const PointerType *PT = cast<PointerType>(GEP->getOperand(0)->getType()); 10300ff39b3feb10477c224138156941234f5fa46f58Evan Cheng const ArrayType *AT = dyn_cast<ArrayType>(PT->getElementType()); 10310582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (AT == 0 || AT->getElementType() != Type::Int8Ty) 10320582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10330ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10340ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Check to make sure that the first operand of the GEP is an integer and 10350ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // has value 0 so that we are sure we're indexing into the initializer. 10360ff39b3feb10477c224138156941234f5fa46f58Evan Cheng ConstantInt *FirstIdx = dyn_cast<ConstantInt>(GEP->getOperand(1)); 10370582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (FirstIdx == 0 || !FirstIdx->isZero()) 10380582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10390ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10400ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // If the second index isn't a ConstantInt, then this is a variable index 10410ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // into the array. If this occurs, we can't say anything meaningful about 10420ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // the string. 10430ff39b3feb10477c224138156941234f5fa46f58Evan Cheng uint64_t StartIdx = 0; 10440582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2))) 10450ff39b3feb10477c224138156941234f5fa46f58Evan Cheng StartIdx = CI->getZExtValue(); 10460582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling else 10470582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10480582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return GetConstantStringInfo(GEP->getOperand(0), Str, StartIdx+Offset, 10490ff39b3feb10477c224138156941234f5fa46f58Evan Cheng StopAtNul); 10500ff39b3feb10477c224138156941234f5fa46f58Evan Cheng } 10510ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10520ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // The GEP instruction, constant or instruction, must reference a global 10530ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // variable that is a constant and is initialized. The referenced constant 10540ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // initializer is the array that we'll use for optimization. 10550ff39b3feb10477c224138156941234f5fa46f58Evan Cheng GlobalVariable* GV = dyn_cast<GlobalVariable>(V); 10560582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (!GV || !GV->isConstant() || !GV->hasInitializer()) 10570582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10580ff39b3feb10477c224138156941234f5fa46f58Evan Cheng Constant *GlobalInit = GV->getInitializer(); 10590ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10600ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Handle the ConstantAggregateZero case 10610582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (isa<ConstantAggregateZero>(GlobalInit)) { 10620ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // This is a degenerate case. The initializer is constant zero so the 10630ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // length of the string must be zero. 10640582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling Str.clear(); 10650582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return true; 10660582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling } 10670ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10680ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Must be a Constant Array 10690ff39b3feb10477c224138156941234f5fa46f58Evan Cheng ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit); 10700582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (Array == 0 || Array->getType()->getElementType() != Type::Int8Ty) 10710582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10720ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10730ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Get the number of elements in the array 10740ff39b3feb10477c224138156941234f5fa46f58Evan Cheng uint64_t NumElts = Array->getType()->getNumElements(); 10750ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10760582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (Offset > NumElts) 10770582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10780ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10790ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Traverse the constant array from 'Offset' which is the place the GEP refers 10800ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // to in the array. 10810582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling Str.reserve(NumElts-Offset); 10820ff39b3feb10477c224138156941234f5fa46f58Evan Cheng for (unsigned i = Offset; i != NumElts; ++i) { 10830ff39b3feb10477c224138156941234f5fa46f58Evan Cheng Constant *Elt = Array->getOperand(i); 10840ff39b3feb10477c224138156941234f5fa46f58Evan Cheng ConstantInt *CI = dyn_cast<ConstantInt>(Elt); 10850582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (!CI) // This array isn't suitable, non-int initializer. 10860582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10870ff39b3feb10477c224138156941234f5fa46f58Evan Cheng if (StopAtNul && CI->isZero()) 10880582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return true; // we found end of string, success! 10890582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling Str += (char)CI->getZExtValue(); 10900ff39b3feb10477c224138156941234f5fa46f58Evan Cheng } 10910582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling 10920ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // The array isn't null terminated, but maybe this is a memcpy, not a strcpy. 10930582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return true; 10940ff39b3feb10477c224138156941234f5fa46f58Evan Cheng} 1095