ValueTracking.cpp revision a7235ea7245028a0723e8ab7fd011386b3900777
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" 2076f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson#include "llvm/LLVMContext.h" 21ca178908c8dc2303a1fb54a8a93bab0f0b964e11Dan Gohman#include "llvm/Operator.h" 220582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling#include "llvm/Target/TargetData.h" 23173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner#include "llvm/Support/GetElementPtrTypeIterator.h" 24173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner#include "llvm/Support/MathExtras.h" 2532a9e7a2654c4aab2e617fbe53140492b3d38066Chris Lattner#include <cstring> 26173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattnerusing namespace llvm; 27173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 28173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// ComputeMaskedBits - Determine which of the bits specified in Mask are 29173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// known to be either zero or one and return them in the KnownZero/KnownOne 30173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// bit sets. This code only analyzes bits in Mask, in order to short-circuit 31173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// processing. 32173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// NOTE: we cannot consider 'undef' to be "IsZero" here. The problem is that 33173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// we cannot optimize based on the assumption that it is zero without changing 34173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// it to be an explicit zero. If we don't change it to zero, other code could 35173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// optimized based on the contradictory assumption that it is non-zero. 36173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// Because instcombine aggressively folds operations with undef args anyway, 37173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// this won't lose us code quality. 38173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattnervoid llvm::ComputeMaskedBits(Value *V, const APInt &Mask, 39173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt &KnownZero, APInt &KnownOne, 40173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TargetData *TD, unsigned Depth) { 419004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman const unsigned MaxDepth = 6; 42173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert(V && "No Value?"); 439004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman assert(Depth <= MaxDepth && "Limit Search Depth"); 4479abedb83a4dd7d3583c7ca6df8283079acc3ba5Chris Lattner unsigned BitWidth = Mask.getBitWidth(); 456de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman assert((V->getType()->isIntOrIntVector() || isa<PointerType>(V->getType())) && 46173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner "Not integer or pointer type!"); 476de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman assert((!TD || 486de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman TD->getTypeSizeInBits(V->getType()->getScalarType()) == BitWidth) && 496de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman (!V->getType()->isIntOrIntVector() || 506de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman V->getType()->getScalarSizeInBits() == BitWidth) && 51173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.getBitWidth() == BitWidth && 52173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.getBitWidth() == BitWidth && 53173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner "V, Mask, KnownOne and KnownZero should have same BitWidth"); 54173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 55173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 56173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // We know all of the bits for a constant! 57173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne = CI->getValue() & Mask; 58173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = ~KnownOne & Mask; 59173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 60173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 616de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman // Null and aggregate-zero are all-zeros. 626de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman if (isa<ConstantPointerNull>(V) || 636de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman isa<ConstantAggregateZero>(V)) { 64173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.clear(); 65173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = Mask; 66173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 67173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 686de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman // Handle a constant vector by taking the intersection of the known bits of 696de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman // each element. 706de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) { 716de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman KnownZero.set(); KnownOne.set(); 726de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) { 736de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman APInt KnownZero2(BitWidth, 0), KnownOne2(BitWidth, 0); 746de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman ComputeMaskedBits(CV->getOperand(i), Mask, KnownZero2, KnownOne2, 756de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman TD, Depth); 766de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman KnownZero &= KnownZero2; 776de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman KnownOne &= KnownOne2; 786de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman } 796de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman return; 806de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman } 81173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // The address of an aligned GlobalValue has trailing zeros. 82173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) { 83173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned Align = GV->getAlignment(); 84173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Align == 0 && TD && GV->getType()->getElementType()->isSized()) 85173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Align = TD->getPrefTypeAlignment(GV->getType()->getElementType()); 86173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Align > 0) 87173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = Mask & APInt::getLowBitsSet(BitWidth, 88173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner CountTrailingZeros_32(Align)); 89173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner else 90173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.clear(); 91173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.clear(); 92173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 93173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 94173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 95173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.clear(); KnownOne.clear(); // Start out not knowing anything. 96173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 979004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman if (Depth == MaxDepth || Mask == 0) 98173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; // Limit search depth. 99173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 100ca178908c8dc2303a1fb54a8a93bab0f0b964e11Dan Gohman Operator *I = dyn_cast<Operator>(V); 101173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (!I) return; 102173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 103173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt KnownZero2(KnownZero), KnownOne2(KnownOne); 104ca178908c8dc2303a1fb54a8a93bab0f0b964e11Dan Gohman switch (I->getOpcode()) { 105173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner default: break; 106173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::And: { 107173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If either the LHS or the RHS are Zero, the result is zero. 108173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1); 109173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2(Mask & ~KnownZero); 110173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, 111173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 112173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 113173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); 114173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 115173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Output known-1 bits are only known if set in both the LHS & RHS. 116173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne &= KnownOne2; 117173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Output known-0 are known to be clear if zero in either the LHS | RHS. 118173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= KnownZero2; 119173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 120173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 121173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Or: { 122173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1); 123173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2(Mask & ~KnownOne); 124173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, 125173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 126173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 127173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); 128173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 129173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Output known-0 bits are only known if clear in both the LHS & RHS. 130173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero &= KnownZero2; 131173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Output known-1 are known to be set if set in either the LHS | RHS. 132173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne |= KnownOne2; 133173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 134173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 135173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Xor: { 136173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1); 137173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, TD, 138173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 139173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 140173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); 141173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 142173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Output known-0 bits are known if clear or set in both the LHS & RHS. 143173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt KnownZeroOut = (KnownZero & KnownZero2) | (KnownOne & KnownOne2); 144173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Output known-1 are known to be set if set in only one of the LHS, RHS. 145173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne = (KnownZero & KnownOne2) | (KnownOne & KnownZero2); 146173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = KnownZeroOut; 147173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 148173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 149173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Mul: { 150173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2 = APInt::getAllOnesValue(BitWidth); 151173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), Mask2, KnownZero, KnownOne, TD,Depth+1); 152173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, 153173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 154173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 155173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); 156173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 157173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If low bits are zero in either operand, output low known-0 bits. 158173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Also compute a conserative estimate for high known-0 bits. 159173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // More trickiness is possible, but this is sufficient for the 160173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // interesting case of alignment computation. 161173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.clear(); 162173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned TrailZ = KnownZero.countTrailingOnes() + 163173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero2.countTrailingOnes(); 164173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned LeadZ = std::max(KnownZero.countLeadingOnes() + 165173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero2.countLeadingOnes(), 166173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner BitWidth) - BitWidth; 167173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 168173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TrailZ = std::min(TrailZ, BitWidth); 169173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LeadZ = std::min(LeadZ, BitWidth); 170173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) | 171173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt::getHighBitsSet(BitWidth, LeadZ); 172173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero &= Mask; 173173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 174173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 175173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::UDiv: { 176173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // For the purposes of computing leading zeros we can conservatively 177173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // treat a udiv as a logical right shift by the power of 2 known to 178173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // be less than the denominator. 179173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt AllOnes = APInt::getAllOnesValue(BitWidth); 180173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), 181173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner AllOnes, KnownZero2, KnownOne2, TD, Depth+1); 182173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned LeadZ = KnownZero2.countLeadingOnes(); 183173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 184173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne2.clear(); 185173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero2.clear(); 186173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), 187173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner AllOnes, KnownZero2, KnownOne2, TD, Depth+1); 188173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned RHSUnknownLeadingOnes = KnownOne2.countLeadingZeros(); 189173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (RHSUnknownLeadingOnes != BitWidth) 190173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LeadZ = std::min(BitWidth, 191173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LeadZ + BitWidth - RHSUnknownLeadingOnes - 1); 192173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 193173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ) & Mask; 194173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 195173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 196173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Select: 197173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(2), Mask, KnownZero, KnownOne, TD, Depth+1); 198173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), Mask, KnownZero2, KnownOne2, TD, 199173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 200173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 201173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); 202173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 203173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Only known if known in both the LHS and RHS. 204173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne &= KnownOne2; 205173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero &= KnownZero2; 206173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 207173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::FPTrunc: 208173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::FPExt: 209173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::FPToUI: 210173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::FPToSI: 211173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::SIToFP: 212173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::UIToFP: 213173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; // Can't work with floating point. 214173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::PtrToInt: 215173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::IntToPtr: 216173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // We can't handle these if we don't know the pointer size. 217173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (!TD) return; 218173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // FALL THROUGH and handle them the same as zext/trunc. 219173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::ZExt: 220173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Trunc: { 221173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Note that we handle pointer operands here because of inttoptr/ptrtoint 222173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // which fall through here. 223173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner const Type *SrcTy = I->getOperand(0)->getType(); 22479abedb83a4dd7d3583c7ca6df8283079acc3ba5Chris Lattner unsigned SrcBitWidth = TD ? 225173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TD->getTypeSizeInBits(SrcTy) : 2266de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman SrcTy->getScalarSizeInBits(); 227173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt MaskIn(Mask); 228173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner MaskIn.zextOrTrunc(SrcBitWidth); 229173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.zextOrTrunc(SrcBitWidth); 230173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.zextOrTrunc(SrcBitWidth); 231173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, TD, 232173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 233173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.zextOrTrunc(BitWidth); 234173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.zextOrTrunc(BitWidth); 235173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Any top bits are known to be zero. 236173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (BitWidth > SrcBitWidth) 237173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth); 238173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 239173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 240173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::BitCast: { 241173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner const Type *SrcTy = I->getOperand(0)->getType(); 2420dabb0b177089202dae485d085ed15bd41ef29e6Chris Lattner if ((SrcTy->isInteger() || isa<PointerType>(SrcTy)) && 2430dabb0b177089202dae485d085ed15bd41ef29e6Chris Lattner // TODO: For now, not handling conversions like: 2440dabb0b177089202dae485d085ed15bd41ef29e6Chris Lattner // (bitcast i64 %x to <2 x i32>) 2450dabb0b177089202dae485d085ed15bd41ef29e6Chris Lattner !isa<VectorType>(I->getType())) { 246173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, TD, 247173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 248173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 249173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 250173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 251173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 252173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::SExt: { 253173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Compute the bits in the result that are not present in the input. 254173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType()); 25579abedb83a4dd7d3583c7ca6df8283079acc3ba5Chris Lattner unsigned SrcBitWidth = SrcTy->getBitWidth(); 256173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 257173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt MaskIn(Mask); 258173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner MaskIn.trunc(SrcBitWidth); 259173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.trunc(SrcBitWidth); 260173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.trunc(SrcBitWidth); 261173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, TD, 262173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 263173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 264173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero.zext(BitWidth); 265173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.zext(BitWidth); 266173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 267173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If the sign bit of the input is known set or clear, then we know the 268173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // top bits of the result. 269173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (KnownZero[SrcBitWidth-1]) // Input sign bit known zero 270173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth); 271173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner else if (KnownOne[SrcBitWidth-1]) // Input sign bit known set 272173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth); 273173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 274173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 275173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Shl: 276173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0 277173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { 278173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner uint64_t ShiftAmt = SA->getLimitedValue(BitWidth); 279173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2(Mask.lshr(ShiftAmt)); 280173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD, 281173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 282173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 283173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero <<= ShiftAmt; 284173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne <<= ShiftAmt; 285173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= APInt::getLowBitsSet(BitWidth, ShiftAmt); // low bits known 0 286173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 287173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 288173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 289173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::LShr: 290173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0 291173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { 292173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Compute the new bits that are at the top now. 293173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner uint64_t ShiftAmt = SA->getLimitedValue(BitWidth); 294173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 295173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Unsigned shift right. 296173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2(Mask.shl(ShiftAmt)); 297173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero,KnownOne, TD, 298173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 299173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?"); 300173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APIntOps::lshr(KnownZero, ShiftAmt); 301173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne = APIntOps::lshr(KnownOne, ShiftAmt); 302173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // high bits known zero. 303173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= APInt::getHighBitsSet(BitWidth, ShiftAmt); 304173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 305173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 306173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 307173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::AShr: 308173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // (ashr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0 309173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { 310173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Compute the new bits that are at the top now. 311173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner uint64_t ShiftAmt = SA->getLimitedValue(BitWidth); 312173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 313173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Signed shift right. 314173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2(Mask.shl(ShiftAmt)); 315173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD, 316173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 317173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?"); 318173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APIntOps::lshr(KnownZero, ShiftAmt); 319173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne = APIntOps::lshr(KnownOne, ShiftAmt); 320173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 321173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt)); 322173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (KnownZero[BitWidth-ShiftAmt-1]) // New bits are known zero. 323173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= HighBits; 324173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner else if (KnownOne[BitWidth-ShiftAmt-1]) // New bits are known one. 325173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne |= HighBits; 326173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 327173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 328173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 329173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Sub: { 330173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *CLHS = dyn_cast<ConstantInt>(I->getOperand(0))) { 331173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // We know that the top bits of C-X are clear if X contains less bits 332173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // than C (i.e. no wrap-around can happen). For example, 20-X is 333173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // positive if we can prove that X is >= 0 and < 16. 334173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (!CLHS->getValue().isNegative()) { 335173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned NLZ = (CLHS->getValue()+1).countLeadingZeros(); 336173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // NLZ can't be BitWidth with no sign bit 337173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt MaskV = APInt::getHighBitsSet(BitWidth, NLZ+1); 338173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), MaskV, KnownZero2, KnownOne2, 339173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TD, Depth+1); 340173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 341173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If all of the MaskV bits are known to be zero, then we know the 342173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // output top bits are zero, because we now know that the output is 343173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // from [0-C]. 344173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if ((KnownZero2 & MaskV) == MaskV) { 345173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned NLZ2 = CLHS->getValue().countLeadingZeros(); 346173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Top bits known zero. 347173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APInt::getHighBitsSet(BitWidth, NLZ2) & Mask; 348173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 349173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 350173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 351173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 352173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // fall through 353173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Add: { 3543925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // If one of the operands has trailing zeros, than the bits that the 3553925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // other operand has in those bit positions will be preserved in the 3563925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // result. For an add, this works with either operand. For a subtract, 3573925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // this only works if the known zeros are in the right operand. 3583925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0); 3593925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman APInt Mask2 = APInt::getLowBitsSet(BitWidth, 3603925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman BitWidth - Mask.countLeadingZeros()); 3613925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman ComputeMaskedBits(I->getOperand(0), Mask2, LHSKnownZero, LHSKnownOne, TD, 362173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 3633925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman assert((LHSKnownZero & LHSKnownOne) == 0 && 3643925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman "Bits known to be one AND zero?"); 3653925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman unsigned LHSKnownZeroOut = LHSKnownZero.countTrailingOnes(); 366173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 367173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), Mask2, KnownZero2, KnownOne2, TD, 368173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 369173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); 3703925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman unsigned RHSKnownZeroOut = KnownZero2.countTrailingOnes(); 371173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 3723925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // Determine which operand has more trailing zeros, and use that 3733925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // many bits from the other operand. 3743925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman if (LHSKnownZeroOut > RHSKnownZeroOut) { 375ca178908c8dc2303a1fb54a8a93bab0f0b964e11Dan Gohman if (I->getOpcode() == Instruction::Add) { 3763925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman APInt Mask = APInt::getLowBitsSet(BitWidth, LHSKnownZeroOut); 3773925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman KnownZero |= KnownZero2 & Mask; 3783925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman KnownOne |= KnownOne2 & Mask; 3793925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman } else { 3803925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // If the known zeros are in the left operand for a subtract, 3813925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman // fall back to the minimum known zeros in both operands. 3823925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman KnownZero |= APInt::getLowBitsSet(BitWidth, 3833925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman std::min(LHSKnownZeroOut, 3843925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman RHSKnownZeroOut)); 3853925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman } 3863925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman } else if (RHSKnownZeroOut >= LHSKnownZeroOut) { 3873925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman APInt Mask = APInt::getLowBitsSet(BitWidth, RHSKnownZeroOut); 3883925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman KnownZero |= LHSKnownZero & Mask; 3893925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman KnownOne |= LHSKnownOne & Mask; 3903925043af0ecf1f0a6158c5007c1186797a252cbDan Gohman } 391173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return; 392173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 393173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::SRem: 394173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) { 395173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt RA = Rem->getValue(); 396173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (RA.isPowerOf2() || (-RA).isPowerOf2()) { 397173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt LowBits = RA.isStrictlyPositive() ? (RA - 1) : ~RA; 398173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2 = LowBits | APInt::getSignBit(BitWidth); 399173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, 400173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 401173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 402a60832b0187642d01fd726dc766cd62587f6add0Dan Gohman // If the sign bit of the first operand is zero, the sign bit of 403a60832b0187642d01fd726dc766cd62587f6add0Dan Gohman // the result is zero. If the first operand has no one bits below 404a60832b0187642d01fd726dc766cd62587f6add0Dan Gohman // the second operand's single 1 bit, its sign will be zero. 405173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (KnownZero2[BitWidth-1] || ((KnownZero2 & LowBits) == LowBits)) 406173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero2 |= ~LowBits; 407173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 408173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= KnownZero2 & Mask; 409173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 410173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?"); 411173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 412173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 413173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 414173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::URem: { 415173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) { 416173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt RA = Rem->getValue(); 417173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (RA.isPowerOf2()) { 418173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt LowBits = (RA - 1); 419173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2 = LowBits & Mask; 420173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero |= ~LowBits & Mask; 421173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD, 422173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 423173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?"); 424173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 425173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 426173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 427173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 428173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Since the result is less than or equal to either operand, any leading 429173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // zero bits in either operand must also exist in the result. 430173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt AllOnes = APInt::getAllOnesValue(BitWidth); 431173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), AllOnes, KnownZero, KnownOne, 432173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TD, Depth+1); 433173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(1), AllOnes, KnownZero2, KnownOne2, 434173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TD, Depth+1); 435173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 43679abedb83a4dd7d3583c7ca6df8283079acc3ba5Chris Lattner unsigned Leaders = std::max(KnownZero.countLeadingOnes(), 437173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero2.countLeadingOnes()); 438173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownOne.clear(); 439173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APInt::getHighBitsSet(BitWidth, Leaders) & Mask; 440173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 441173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 442173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 443173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Alloca: 444173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Malloc: { 445173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner AllocationInst *AI = cast<AllocationInst>(V); 446173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned Align = AI->getAlignment(); 447173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Align == 0 && TD) { 448173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (isa<AllocaInst>(AI)) 4490f2831c820151aa6f2cd6a8bd7b6b633b1035524Chris Lattner Align = TD->getABITypeAlignment(AI->getType()->getElementType()); 450173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner else if (isa<MallocInst>(AI)) { 451173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Malloc returns maximally aligned memory. 452173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Align = TD->getABITypeAlignment(AI->getType()->getElementType()); 453173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Align = 454173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner std::max(Align, 455173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner (unsigned)TD->getABITypeAlignment(Type::DoubleTy)); 456173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Align = 457173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner std::max(Align, 458173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner (unsigned)TD->getABITypeAlignment(Type::Int64Ty)); 459173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 460173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 461173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 462173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Align > 0) 463173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = Mask & APInt::getLowBitsSet(BitWidth, 464173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner CountTrailingZeros_32(Align)); 465173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 466173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 467173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::GetElementPtr: { 468173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Analyze all of the subscripts of this getelementptr instruction 469173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // to determine if we can prove known low zero bits. 470173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt LocalMask = APInt::getAllOnesValue(BitWidth); 471173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt LocalKnownZero(BitWidth, 0), LocalKnownOne(BitWidth, 0); 472173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(I->getOperand(0), LocalMask, 473173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LocalKnownZero, LocalKnownOne, TD, Depth+1); 474173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned TrailZ = LocalKnownZero.countTrailingOnes(); 475173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 476173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner gep_type_iterator GTI = gep_type_begin(I); 477173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i, ++GTI) { 478173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Value *Index = I->getOperand(i); 479173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (const StructType *STy = dyn_cast<StructType>(*GTI)) { 480173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Handle struct member offset arithmetic. 481173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (!TD) return; 482173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner const StructLayout *SL = TD->getStructLayout(STy); 483173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned Idx = cast<ConstantInt>(Index)->getZExtValue(); 484173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner uint64_t Offset = SL->getElementOffset(Idx); 485173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TrailZ = std::min(TrailZ, 486173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner CountTrailingZeros_64(Offset)); 487173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } else { 488173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Handle array index arithmetic. 489173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner const Type *IndexedTy = GTI.getIndexedType(); 490173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (!IndexedTy->isSized()) return; 4916de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman unsigned GEPOpiBits = Index->getType()->getScalarSizeInBits(); 492777d2306b36816a53bc1ae1244c0dc7d998ae691Duncan Sands uint64_t TypeSize = TD ? TD->getTypeAllocSize(IndexedTy) : 1; 493173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LocalMask = APInt::getAllOnesValue(GEPOpiBits); 494173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LocalKnownZero = LocalKnownOne = APInt(GEPOpiBits, 0); 495173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(Index, LocalMask, 496173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner LocalKnownZero, LocalKnownOne, TD, Depth+1); 497173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TrailZ = std::min(TrailZ, 49879abedb83a4dd7d3583c7ca6df8283079acc3ba5Chris Lattner unsigned(CountTrailingZeros_64(TypeSize) + 49979abedb83a4dd7d3583c7ca6df8283079acc3ba5Chris Lattner LocalKnownZero.countTrailingOnes())); 500173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 501173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 502173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 503173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) & Mask; 504173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 505173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 506173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::PHI: { 507173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner PHINode *P = cast<PHINode>(I); 508173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Handle the case of a simple two-predecessor recurrence PHI. 509173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // There's a lot more that could theoretically be done here, but 510173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // this is sufficient to catch some interesting cases. 511173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (P->getNumIncomingValues() == 2) { 512173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner for (unsigned i = 0; i != 2; ++i) { 513173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Value *L = P->getIncomingValue(i); 514173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Value *R = P->getIncomingValue(!i); 515ca178908c8dc2303a1fb54a8a93bab0f0b964e11Dan Gohman Operator *LU = dyn_cast<Operator>(L); 516173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (!LU) 517173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner continue; 518ca178908c8dc2303a1fb54a8a93bab0f0b964e11Dan Gohman unsigned Opcode = LU->getOpcode(); 519173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Check for operations that have the property that if 520173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // both their operands have low zero bits, the result 521173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // will have low zero bits. 522173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Opcode == Instruction::Add || 523173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Opcode == Instruction::Sub || 524173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Opcode == Instruction::And || 525173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Opcode == Instruction::Or || 526173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Opcode == Instruction::Mul) { 527173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Value *LL = LU->getOperand(0); 528173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Value *LR = LU->getOperand(1); 529173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Find a recurrence. 530173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (LL == I) 531173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner L = LR; 532173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner else if (LR == I) 533173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner L = LL; 534173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner else 535173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 536173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Ok, we have a PHI of the form L op= R. Check for low 537173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // zero bits. 538173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask2 = APInt::getAllOnesValue(BitWidth); 539173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(R, Mask2, KnownZero2, KnownOne2, TD, Depth+1); 540173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Mask2 = APInt::getLowBitsSet(BitWidth, 541173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero2.countTrailingOnes()); 542c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene 543c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene // We need to take the minimum number of known bits 544c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene APInt KnownZero3(KnownZero), KnownOne3(KnownOne); 545c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene ComputeMaskedBits(L, Mask2, KnownZero3, KnownOne3, TD, Depth+1); 546c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene 547173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = Mask & 548173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt::getLowBitsSet(BitWidth, 549c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene std::min(KnownZero2.countTrailingOnes(), 550c714f1309049b2fd9e4ab68c8a7b480c63a4be0cDavid Greene KnownZero3.countTrailingOnes())); 551173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 552173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 553173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 554173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 5559004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman 5569004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // Otherwise take the unions of the known bit sets of the operands, 5579004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // taking conservative care to avoid excessive recursion. 5589004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman if (Depth < MaxDepth - 1 && !KnownZero && !KnownOne) { 5599004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownZero = APInt::getAllOnesValue(BitWidth); 5609004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownOne = APInt::getAllOnesValue(BitWidth); 5619004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i) { 5629004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // Skip direct self references. 5639004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman if (P->getIncomingValue(i) == P) continue; 5649004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman 5659004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownZero2 = APInt(BitWidth, 0); 5669004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownOne2 = APInt(BitWidth, 0); 5679004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // Recurse, but cap the recursion to one level, because we don't 5689004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // want to waste time spinning around in loops. 5699004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman ComputeMaskedBits(P->getIncomingValue(i), KnownZero | KnownOne, 5709004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownZero2, KnownOne2, TD, MaxDepth-1); 5719004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownZero &= KnownZero2; 5729004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman KnownOne &= KnownOne2; 5739004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // If all bits have been ruled out, there's no need to check 5749004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman // more operands. 5759004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman if (!KnownZero && !KnownOne) 5769004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman break; 5779004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman } 5789004c8afd4bf7b3f27f4a4f8fd069379afa97c83Dan Gohman } 579173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 580173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 581173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Call: 582173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { 583173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner switch (II->getIntrinsicID()) { 584173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner default: break; 585173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Intrinsic::ctpop: 586173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Intrinsic::ctlz: 587173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Intrinsic::cttz: { 588173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned LowBits = Log2_32(BitWidth)+1; 589173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - LowBits); 590173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 591173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 592173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 593173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 594173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 595173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 596173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner} 597173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 598173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use 599173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// this predicate to simplify operations downstream. Mask is known to be zero 600173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// for bits that V cannot have. 601173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattnerbool llvm::MaskedValueIsZero(Value *V, const APInt &Mask, 602173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TargetData *TD, unsigned Depth) { 603173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt KnownZero(Mask.getBitWidth(), 0), KnownOne(Mask.getBitWidth(), 0); 604173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD, Depth); 605173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 606173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return (KnownZero & Mask) == Mask; 607173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner} 608173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 609173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 610173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 611173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// ComputeNumSignBits - Return the number of times the sign bit of the 612173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// register is replicated into the other bits. We know that at least 1 bit 613173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// is always equal to the sign bit (itself), but other cases can give us 614173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// information. For example, immediately after an "ashr X, 2", we know that 615173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// the top 3 bits are all equal to each other, so we return 3. 616173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// 617173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// 'Op' must have a scalar integer type. 618173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner/// 619173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattnerunsigned llvm::ComputeNumSignBits(Value *V, TargetData *TD, unsigned Depth) { 620bd5ce52740700bb482fb2b5a03bce781acbf2941Dan Gohman assert((TD || V->getType()->isIntOrIntVector()) && 621bd5ce52740700bb482fb2b5a03bce781acbf2941Dan Gohman "ComputeNumSignBits requires a TargetData object to operate " 622bd5ce52740700bb482fb2b5a03bce781acbf2941Dan Gohman "on non-integer values!"); 6236de29f8d960505421d61c80cdb738e16720b6c0eDan Gohman const Type *Ty = V->getType(); 624bd5ce52740700bb482fb2b5a03bce781acbf2941Dan Gohman unsigned TyBits = TD ? TD->getTypeSizeInBits(V->getType()->getScalarType()) : 625bd5ce52740700bb482fb2b5a03bce781acbf2941Dan Gohman Ty->getScalarSizeInBits(); 626173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned Tmp, Tmp2; 627173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned FirstAnswer = 1; 628173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 629d82e511aec0ea27ddd4c1e504b37f689796e965fChris Lattner // Note that ConstantInt is handled by the general ComputeMaskedBits case 630d82e511aec0ea27ddd4c1e504b37f689796e965fChris Lattner // below. 631d82e511aec0ea27ddd4c1e504b37f689796e965fChris Lattner 632173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Depth == 6) 633173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return 1; // Limit search depth. 634173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 635ca178908c8dc2303a1fb54a8a93bab0f0b964e11Dan Gohman Operator *U = dyn_cast<Operator>(V); 636ca178908c8dc2303a1fb54a8a93bab0f0b964e11Dan Gohman switch (Operator::getOpcode(V)) { 637173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner default: break; 638173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::SExt: 639173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = TyBits-cast<IntegerType>(U->getOperand(0)->getType())->getBitWidth(); 640173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return ComputeNumSignBits(U->getOperand(0), TD, Depth+1) + Tmp; 641173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 642173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::AShr: 643173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1); 644173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // ashr X, C -> adds C sign bits. 645173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *C = dyn_cast<ConstantInt>(U->getOperand(1))) { 646173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp += C->getZExtValue(); 647173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp > TyBits) Tmp = TyBits; 648173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 649173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return Tmp; 650173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Shl: 651173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *C = dyn_cast<ConstantInt>(U->getOperand(1))) { 652173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // shl destroys sign bits. 653173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1); 654173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (C->getZExtValue() >= TyBits || // Bad shift. 655173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner C->getZExtValue() >= Tmp) break; // Shifted all sign bits out. 656173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return Tmp - C->getZExtValue(); 657173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 658173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 659173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::And: 660173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Or: 661173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Xor: // NOT is handled here. 662173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Logical binary ops preserve the number of sign bits at the worst. 663173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1); 664173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp != 1) { 665173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp2 = ComputeNumSignBits(U->getOperand(1), TD, Depth+1); 666173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner FirstAnswer = std::min(Tmp, Tmp2); 667173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // We computed what we know about the sign bits as our first 668173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // answer. Now proceed to the generic code that uses 669173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // ComputeMaskedBits, and pick whichever answer is better. 670173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 671173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 672173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 673173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Select: 674173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = ComputeNumSignBits(U->getOperand(1), TD, Depth+1); 675173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp == 1) return 1; // Early out. 676173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp2 = ComputeNumSignBits(U->getOperand(2), TD, Depth+1); 677173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return std::min(Tmp, Tmp2); 678173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 679173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Add: 680173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Add can have at most one carry bit. Thus we know that the output 681173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // is, at worst, one more bit than the inputs. 682173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1); 683173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp == 1) return 1; // Early out. 684173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 685173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Special case decrementing a value (ADD X, -1): 6860001e56f15215ae4bc5fffb82eec5c4828b888f0Dan Gohman if (ConstantInt *CRHS = dyn_cast<ConstantInt>(U->getOperand(1))) 687173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (CRHS->isAllOnesValue()) { 688173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0); 689173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask = APInt::getAllOnesValue(TyBits); 690173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(U->getOperand(0), Mask, KnownZero, KnownOne, TD, 691173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Depth+1); 692173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 693173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If the input is known to be 0 or 1, the output is 0/-1, which is all 694173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // sign bits set. 695173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if ((KnownZero | APInt(TyBits, 1)) == Mask) 696173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return TyBits; 697173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 698173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If we are subtracting one from a positive number, there is no carry 699173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // out of the result. 700173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (KnownZero.isNegative()) 701173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return Tmp; 702173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 703173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 704173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp2 = ComputeNumSignBits(U->getOperand(1), TD, Depth+1); 705173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp2 == 1) return 1; 706173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return std::min(Tmp, Tmp2)-1; 707173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 708173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 709173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Sub: 710173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp2 = ComputeNumSignBits(U->getOperand(1), TD, Depth+1); 711173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp2 == 1) return 1; 712173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 713173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Handle NEG. 714173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (ConstantInt *CLHS = dyn_cast<ConstantInt>(U->getOperand(0))) 715173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (CLHS->isNullValue()) { 716173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0); 717173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask = APInt::getAllOnesValue(TyBits); 718173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(U->getOperand(1), Mask, KnownZero, KnownOne, 719173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner TD, Depth+1); 720173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If the input is known to be 0 or 1, the output is 0/-1, which is all 721173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // sign bits set. 722173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if ((KnownZero | APInt(TyBits, 1)) == Mask) 723173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return TyBits; 724173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 725173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // If the input is known to be positive (the sign bit is known clear), 726173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // the output of the NEG has the same number of sign bits as the input. 727173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (KnownZero.isNegative()) 728173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return Tmp2; 729173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 730173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Otherwise, we treat this like a SUB. 731173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 732173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 733173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Sub can have at most one carry bit. Thus we know that the output 734173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // is, at worst, one more bit than the inputs. 735173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1); 736173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (Tmp == 1) return 1; // Early out. 737173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return std::min(Tmp, Tmp2)-1; 738173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 739173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner case Instruction::Trunc: 740173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // FIXME: it's tricky to do anything useful for this, but it is an important 741173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // case for targets like X86. 742173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner break; 743173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 744173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 745173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Finally, if we can prove that the top bits of the result are 0's or 1's, 746173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // use this information. 747173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0); 748173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner APInt Mask = APInt::getAllOnesValue(TyBits); 749173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD, Depth); 750173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 751173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner if (KnownZero.isNegative()) { // sign bit is 0 752173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Mask = KnownZero; 753173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } else if (KnownOne.isNegative()) { // sign bit is 1; 754173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Mask = KnownOne; 755173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } else { 756173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Nothing known. 757173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return FirstAnswer; 758173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner } 759173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 760173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Okay, we know that the sign bit in Mask is set. Use CLZ to determine 761173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // the number of identical bits in the top of the input value. 762173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Mask = ~Mask; 763173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner Mask <<= Mask.getBitWidth()-TyBits; 764173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // Return # leading zeros. We use 'min' here in case Val was zero before 765173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner // shifting. We don't want to return '64' as for an i32 "0". 766173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner return std::max(FirstAnswer, std::min(TyBits, Mask.countLeadingZeros())); 767173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner} 768833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 769833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner/// CannotBeNegativeZero - Return true if we can prove that the specified FP 770833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner/// value is never equal to -0.0. 771833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner/// 772833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner/// NOTE: this function will need to be revisited when we support non-default 773833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner/// rounding modes! 774833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner/// 775833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattnerbool llvm::CannotBeNegativeZero(const Value *V, unsigned Depth) { 776833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (const ConstantFP *CFP = dyn_cast<ConstantFP>(V)) 777833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner return !CFP->getValueAPF().isNegZero(); 778833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 779833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (Depth == 6) 780833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner return 1; // Limit search depth. 781833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 782ca178908c8dc2303a1fb54a8a93bab0f0b964e11Dan Gohman const Operator *I = dyn_cast<Operator>(V); 783833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (I == 0) return false; 784833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 785833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner // (add x, 0.0) is guaranteed to return +0.0, not -0.0. 786ae3a0be92e33bc716722aa600983fc1535acb122Dan Gohman if (I->getOpcode() == Instruction::FAdd && 787833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner isa<ConstantFP>(I->getOperand(1)) && 788833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner cast<ConstantFP>(I->getOperand(1))->isNullValue()) 789833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner return true; 790833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 791833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner // sitofp and uitofp turn into +0.0 for zero. 792833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (isa<SIToFPInst>(I) || isa<UIToFPInst>(I)) 793833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner return true; 794833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 795833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) 796833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner // sqrt(-0.0) = -0.0, no other negative results are possible. 797833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (II->getIntrinsicID() == Intrinsic::sqrt) 798833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner return CannotBeNegativeZero(II->getOperand(1), Depth+1); 799833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 800833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (const CallInst *CI = dyn_cast<CallInst>(I)) 801833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (const Function *F = CI->getCalledFunction()) { 802833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner if (F->isDeclaration()) { 803f0443c1eb44d737d9bd78962932fc80f74c6113cDaniel Dunbar // abs(x) != -0.0 804f0443c1eb44d737d9bd78962932fc80f74c6113cDaniel Dunbar if (F->getName() == "abs") return true; 805f0443c1eb44d737d9bd78962932fc80f74c6113cDaniel Dunbar // abs[lf](x) != -0.0 806f0443c1eb44d737d9bd78962932fc80f74c6113cDaniel Dunbar if (F->getName() == "absf") return true; 807f0443c1eb44d737d9bd78962932fc80f74c6113cDaniel Dunbar if (F->getName() == "absl") return true; 808833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner } 809833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner } 810833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 811833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner return false; 812833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner} 813833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner 814b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// This is the recursive version of BuildSubAggregate. It takes a few different 815b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// arguments. Idxs is the index within the nested struct From that we are 816b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// looking at now (which is of type IndexedType). IdxSkip is the number of 817b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// indices from Idxs that should be left out when inserting into the resulting 818b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// struct. To is the result struct built so far, new insertvalue instructions 819b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// build on that. 820b23d5adbc8230167e711070b9298985de4580f30Matthijs KooijmanValue *BuildSubAggregate(Value *From, Value* To, const Type *IndexedType, 821b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman SmallVector<unsigned, 10> &Idxs, 822b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman unsigned IdxSkip, 823e922c0201916e0b980ab3cfe91e1413e68d55647Owen Anderson LLVMContext &Context, 8240a7413dad84887bee51f20d7a5f1c4c1c7bb4c1eMatthijs Kooijman Instruction *InsertBefore) { 825b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman const llvm::StructType *STy = llvm::dyn_cast<llvm::StructType>(IndexedType); 826b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman if (STy) { 8270a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // Save the original To argument so we can modify it 8280a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman Value *OrigTo = To; 829b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // General case, the type indexed by Idxs is a struct 830b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 831b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Process each struct element recursively 832b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman Idxs.push_back(i); 8330a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman Value *PrevTo = To; 834710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman To = BuildSubAggregate(From, To, STy->getElementType(i), Idxs, IdxSkip, 83576f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson Context, InsertBefore); 836b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman Idxs.pop_back(); 8370a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman if (!To) { 8380a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // Couldn't find any inserted value for this index? Cleanup 8390a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman while (PrevTo != OrigTo) { 8400a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman InsertValueInst* Del = cast<InsertValueInst>(PrevTo); 8410a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman PrevTo = Del->getAggregateOperand(); 8420a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman Del->eraseFromParent(); 8430a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman } 8440a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // Stop processing elements 8450a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman break; 8460a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman } 847b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman } 8480a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // If we succesfully found a value for each of our subaggregates 8490a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman if (To) 8500a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman return To; 851b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman } 8520a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // Base case, the type indexed by SourceIdxs is not a struct, or not all of 8530a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // the struct's elements had a value that was inserted directly. In the latter 8540a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // case, perhaps we can't determine each of the subelements individually, but 8550a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // we might be able to find the complete struct somewhere. 8560a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman 8570a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // Find the value that is at that particular spot 85876f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson Value *V = FindInsertedValue(From, Idxs.begin(), Idxs.end(), Context); 8590a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman 8600a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman if (!V) 8610a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman return NULL; 8620a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman 8630a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // Insert the value in the new (sub) aggregrate 8640a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman return llvm::InsertValueInst::Create(To, V, Idxs.begin() + IdxSkip, 8650a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman Idxs.end(), "tmp", InsertBefore); 866b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman} 867b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 868b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// This helper takes a nested struct and extracts a part of it (which is again a 869b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// struct) into a new value. For example, given the struct: 870b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// { a, { b, { c, d }, e } } 871b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// and the indices "1, 1" this returns 872b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// { c, d }. 873b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// 8740a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman// It does this by inserting an insertvalue for each element in the resulting 8750a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman// struct, as opposed to just inserting a single struct. This will only work if 8760a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman// each of the elements of the substruct are known (ie, inserted into From by an 8770a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman// insertvalue instruction somewhere). 878b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman// 8790a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman// All inserted insertvalue instructions are inserted before InsertBefore 880710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs KooijmanValue *BuildSubAggregate(Value *From, const unsigned *idx_begin, 881e922c0201916e0b980ab3cfe91e1413e68d55647Owen Anderson const unsigned *idx_end, LLVMContext &Context, 88276f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson Instruction *InsertBefore) { 883977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman assert(InsertBefore && "Must have someplace to insert!"); 884710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman const Type *IndexedType = ExtractValueInst::getIndexedType(From->getType(), 885710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman idx_begin, 886710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman idx_end); 8879e9a0d5fc26878e51a58a8b57900fcbf952c2691Owen Anderson Value *To = UndefValue::get(IndexedType); 888b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman SmallVector<unsigned, 10> Idxs(idx_begin, idx_end); 889b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman unsigned IdxSkip = Idxs.size(); 890b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 89176f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson return BuildSubAggregate(From, To, IndexedType, Idxs, IdxSkip, 89276f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson Context, InsertBefore); 893b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman} 894b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 895710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman/// FindInsertedValue - Given an aggregrate and an sequence of indices, see if 896710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman/// the scalar value indexed is already around as a register, for example if it 897710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman/// were inserted directly into the aggregrate. 8980a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman/// 8990a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman/// If InsertBefore is not null, this function will duplicate (modified) 9000a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman/// insertvalues when a part of a nested struct is extracted. 901b23d5adbc8230167e711070b9298985de4580f30Matthijs KooijmanValue *llvm::FindInsertedValue(Value *V, const unsigned *idx_begin, 902e922c0201916e0b980ab3cfe91e1413e68d55647Owen Anderson const unsigned *idx_end, LLVMContext &Context, 90376f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson Instruction *InsertBefore) { 904b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Nothing to index? Just return V then (this is useful at the end of our 905b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // recursion) 906b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman if (idx_begin == idx_end) 907b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman return V; 908b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // We have indices, so V should have an indexable type 909b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman assert((isa<StructType>(V->getType()) || isa<ArrayType>(V->getType())) 910b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman && "Not looking at a struct or array?"); 911b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman assert(ExtractValueInst::getIndexedType(V->getType(), idx_begin, idx_end) 912b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman && "Invalid indices for type?"); 913b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman const CompositeType *PTy = cast<CompositeType>(V->getType()); 91476f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson 915b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman if (isa<UndefValue>(V)) 9169e9a0d5fc26878e51a58a8b57900fcbf952c2691Owen Anderson return UndefValue::get(ExtractValueInst::getIndexedType(PTy, 917b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman idx_begin, 918b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman idx_end)); 919b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman else if (isa<ConstantAggregateZero>(V)) 920a7235ea7245028a0723e8ab7fd011386b3900777Owen Anderson return Constant::getNullValue(ExtractValueInst::getIndexedType(PTy, 92176f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson idx_begin, 92276f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson idx_end)); 923b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman else if (Constant *C = dyn_cast<Constant>(V)) { 924b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman if (isa<ConstantArray>(C) || isa<ConstantStruct>(C)) 925b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Recursively process this constant 92676f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson return FindInsertedValue(C->getOperand(*idx_begin), idx_begin + 1, 92776f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson idx_end, Context, InsertBefore); 928b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman } else if (InsertValueInst *I = dyn_cast<InsertValueInst>(V)) { 929b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Loop the indices for the insertvalue instruction in parallel with the 930b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // requested indices 931b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman const unsigned *req_idx = idx_begin; 932710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman for (const unsigned *i = I->idx_begin(), *e = I->idx_end(); 933710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman i != e; ++i, ++req_idx) { 9349954c76f2c89ab3c70bfe8222534621a86f9085aDuncan Sands if (req_idx == idx_end) { 935977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman if (InsertBefore) 9360a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // The requested index identifies a part of a nested aggregate. Handle 9370a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // this specially. For example, 9380a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // %A = insertvalue { i32, {i32, i32 } } undef, i32 10, 1, 0 9390a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // %B = insertvalue { i32, {i32, i32 } } %A, i32 11, 1, 1 9400a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // %C = extractvalue {i32, { i32, i32 } } %B, 1 9410a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // This can be changed into 9420a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // %A = insertvalue {i32, i32 } undef, i32 10, 0 9430a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // %C = insertvalue {i32, i32 } %A, i32 11, 1 9440a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // which allows the unused 0,0 element from the nested struct to be 9450a9aaf46bee75540db16603dd60f7d3bc597842dMatthijs Kooijman // removed. 94676f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson return BuildSubAggregate(V, idx_begin, req_idx, 94776f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson Context, InsertBefore); 948977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman else 949977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman // We can't handle this without inserting insertvalues 950977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman return 0; 9519954c76f2c89ab3c70bfe8222534621a86f9085aDuncan Sands } 952b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 953b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // This insert value inserts something else than what we are looking for. 954b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // See if the (aggregrate) value inserted into has the value we are 955b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // looking for, then. 956b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman if (*req_idx != *i) 957710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman return FindInsertedValue(I->getAggregateOperand(), idx_begin, idx_end, 95876f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson Context, InsertBefore); 959b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman } 960b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // If we end up here, the indices of the insertvalue match with those 961b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // requested (though possibly only partially). Now we recursively look at 962b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // the inserted value, passing any remaining indices. 963710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman return FindInsertedValue(I->getInsertedValueOperand(), req_idx, idx_end, 96476f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson Context, InsertBefore); 965b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman } else if (ExtractValueInst *I = dyn_cast<ExtractValueInst>(V)) { 966b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // If we're extracting a value from an aggregrate that was extracted from 967b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // something else, we can extract from that something else directly instead. 968b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // However, we will need to chain I's indices with the requested indices. 969b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 970b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Calculate the number of indices required 971b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman unsigned size = I->getNumIndices() + (idx_end - idx_begin); 972b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Allocate some space to put the new indices in 9733faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman SmallVector<unsigned, 5> Idxs; 9743faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman Idxs.reserve(size); 975b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Add indices from the extract value instruction 976710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman for (const unsigned *i = I->idx_begin(), *e = I->idx_end(); 9773faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman i != e; ++i) 9783faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman Idxs.push_back(*i); 979b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 980b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Add requested indices 9813faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman for (const unsigned *i = idx_begin, *e = idx_end; i != e; ++i) 9823faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman Idxs.push_back(*i); 983b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 9843faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman assert(Idxs.size() == size 985710eb236e67dc021c51ef5cb5d2eb8768840895aMatthijs Kooijman && "Number of indices added not correct?"); 986b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 9873faf9df08ff389028050bfbccbef571061bf7cc1Matthijs Kooijman return FindInsertedValue(I->getAggregateOperand(), Idxs.begin(), Idxs.end(), 98876f600b205606a055ec35e7d3fd1a99602329d67Owen Anderson Context, InsertBefore); 989b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman } 990b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // Otherwise, we don't know (such as, extracting from a function return value 991b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman // or load instruction) 992b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman return 0; 993b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman} 9940ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 9950ff39b3feb10477c224138156941234f5fa46f58Evan Cheng/// GetConstantStringInfo - This function computes the length of a 9960ff39b3feb10477c224138156941234f5fa46f58Evan Cheng/// null-terminated C string pointed to by V. If successful, it returns true 9970ff39b3feb10477c224138156941234f5fa46f58Evan Cheng/// and returns the string in Str. If unsuccessful, it returns false. 9980582ae99ba75a556d6ff63b254da327d32ba036fBill Wendlingbool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset, 9990582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling bool StopAtNul) { 10000582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling // If V is NULL then return false; 10010582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (V == NULL) return false; 10020ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10030ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Look through bitcast instructions. 10040ff39b3feb10477c224138156941234f5fa46f58Evan Cheng if (BitCastInst *BCI = dyn_cast<BitCastInst>(V)) 10050582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return GetConstantStringInfo(BCI->getOperand(0), Str, Offset, StopAtNul); 10060582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling 10070ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // If the value is not a GEP instruction nor a constant expression with a 10080ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // GEP instruction, then return false because ConstantArray can't occur 10090ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // any other way 10100ff39b3feb10477c224138156941234f5fa46f58Evan Cheng User *GEP = 0; 10110ff39b3feb10477c224138156941234f5fa46f58Evan Cheng if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(V)) { 10120ff39b3feb10477c224138156941234f5fa46f58Evan Cheng GEP = GEPI; 10130ff39b3feb10477c224138156941234f5fa46f58Evan Cheng } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 10140ff39b3feb10477c224138156941234f5fa46f58Evan Cheng if (CE->getOpcode() == Instruction::BitCast) 10150582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return GetConstantStringInfo(CE->getOperand(0), Str, Offset, StopAtNul); 10160582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (CE->getOpcode() != Instruction::GetElementPtr) 10170582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10180ff39b3feb10477c224138156941234f5fa46f58Evan Cheng GEP = CE; 10190ff39b3feb10477c224138156941234f5fa46f58Evan Cheng } 10200ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10210ff39b3feb10477c224138156941234f5fa46f58Evan Cheng if (GEP) { 10220ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Make sure the GEP has exactly three arguments. 10230582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (GEP->getNumOperands() != 3) 10240582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10250582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling 10260ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Make sure the index-ee is a pointer to array of i8. 10270ff39b3feb10477c224138156941234f5fa46f58Evan Cheng const PointerType *PT = cast<PointerType>(GEP->getOperand(0)->getType()); 10280ff39b3feb10477c224138156941234f5fa46f58Evan Cheng const ArrayType *AT = dyn_cast<ArrayType>(PT->getElementType()); 10290582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (AT == 0 || AT->getElementType() != Type::Int8Ty) 10300582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10310ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10320ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Check to make sure that the first operand of the GEP is an integer and 10330ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // has value 0 so that we are sure we're indexing into the initializer. 10340ff39b3feb10477c224138156941234f5fa46f58Evan Cheng ConstantInt *FirstIdx = dyn_cast<ConstantInt>(GEP->getOperand(1)); 10350582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (FirstIdx == 0 || !FirstIdx->isZero()) 10360582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10370ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10380ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // If the second index isn't a ConstantInt, then this is a variable index 10390ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // into the array. If this occurs, we can't say anything meaningful about 10400ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // the string. 10410ff39b3feb10477c224138156941234f5fa46f58Evan Cheng uint64_t StartIdx = 0; 10420582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2))) 10430ff39b3feb10477c224138156941234f5fa46f58Evan Cheng StartIdx = CI->getZExtValue(); 10440582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling else 10450582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10460582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return GetConstantStringInfo(GEP->getOperand(0), Str, StartIdx+Offset, 10470ff39b3feb10477c224138156941234f5fa46f58Evan Cheng StopAtNul); 10480ff39b3feb10477c224138156941234f5fa46f58Evan Cheng } 10490ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10500ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // The GEP instruction, constant or instruction, must reference a global 10510ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // variable that is a constant and is initialized. The referenced constant 10520ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // initializer is the array that we'll use for optimization. 10530ff39b3feb10477c224138156941234f5fa46f58Evan Cheng GlobalVariable* GV = dyn_cast<GlobalVariable>(V); 10540582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (!GV || !GV->isConstant() || !GV->hasInitializer()) 10550582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10560ff39b3feb10477c224138156941234f5fa46f58Evan Cheng Constant *GlobalInit = GV->getInitializer(); 10570ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10580ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Handle the ConstantAggregateZero case 10590582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (isa<ConstantAggregateZero>(GlobalInit)) { 10600ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // This is a degenerate case. The initializer is constant zero so the 10610ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // length of the string must be zero. 10620582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling Str.clear(); 10630582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return true; 10640582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling } 10650ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10660ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Must be a Constant Array 10670ff39b3feb10477c224138156941234f5fa46f58Evan Cheng ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit); 10680582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (Array == 0 || Array->getType()->getElementType() != Type::Int8Ty) 10690582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10700ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10710ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Get the number of elements in the array 10720ff39b3feb10477c224138156941234f5fa46f58Evan Cheng uint64_t NumElts = Array->getType()->getNumElements(); 10730ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10740582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (Offset > NumElts) 10750582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10760ff39b3feb10477c224138156941234f5fa46f58Evan Cheng 10770ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // Traverse the constant array from 'Offset' which is the place the GEP refers 10780ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // to in the array. 10790582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling Str.reserve(NumElts-Offset); 10800ff39b3feb10477c224138156941234f5fa46f58Evan Cheng for (unsigned i = Offset; i != NumElts; ++i) { 10810ff39b3feb10477c224138156941234f5fa46f58Evan Cheng Constant *Elt = Array->getOperand(i); 10820ff39b3feb10477c224138156941234f5fa46f58Evan Cheng ConstantInt *CI = dyn_cast<ConstantInt>(Elt); 10830582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling if (!CI) // This array isn't suitable, non-int initializer. 10840582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return false; 10850ff39b3feb10477c224138156941234f5fa46f58Evan Cheng if (StopAtNul && CI->isZero()) 10860582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return true; // we found end of string, success! 10870582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling Str += (char)CI->getZExtValue(); 10880ff39b3feb10477c224138156941234f5fa46f58Evan Cheng } 10890582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling 10900ff39b3feb10477c224138156941234f5fa46f58Evan Cheng // The array isn't null terminated, but maybe this is a memcpy, not a strcpy. 10910582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling return true; 10920ff39b3feb10477c224138156941234f5fa46f58Evan Cheng} 1093