InstCombineSelect.cpp revision 40bf5e7a6811bf31b6853d2c71c08feed871419b
13c3b7f90a863af43fa63043d396553ecf205351cJohn McCall//===- InstCombineSelect.cpp ----------------------------------------------===// 23c3b7f90a863af43fa63043d396553ecf205351cJohn McCall// 33c3b7f90a863af43fa63043d396553ecf205351cJohn McCall// The LLVM Compiler Infrastructure 43c3b7f90a863af43fa63043d396553ecf205351cJohn McCall// 53c3b7f90a863af43fa63043d396553ecf205351cJohn McCall// This file is distributed under the University of Illinois Open Source 63c3b7f90a863af43fa63043d396553ecf205351cJohn McCall// License. See LICENSE.TXT for details. 73c3b7f90a863af43fa63043d396553ecf205351cJohn McCall// 83c3b7f90a863af43fa63043d396553ecf205351cJohn McCall//===----------------------------------------------------------------------===// 93c3b7f90a863af43fa63043d396553ecf205351cJohn McCall// 103c3b7f90a863af43fa63043d396553ecf205351cJohn McCall// This file implements the visitSelect function. 113c3b7f90a863af43fa63043d396553ecf205351cJohn McCall// 123c3b7f90a863af43fa63043d396553ecf205351cJohn McCall//===----------------------------------------------------------------------===// 133c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 143c3b7f90a863af43fa63043d396553ecf205351cJohn McCall#include "InstCombine.h" 153c3b7f90a863af43fa63043d396553ecf205351cJohn McCall#include "llvm/Support/PatternMatch.h" 163c3b7f90a863af43fa63043d396553ecf205351cJohn McCall#include "llvm/Analysis/InstructionSimplify.h" 173c3b7f90a863af43fa63043d396553ecf205351cJohn McCallusing namespace llvm; 183c3b7f90a863af43fa63043d396553ecf205351cJohn McCallusing namespace PatternMatch; 193c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 203c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// MatchSelectPattern - Pattern match integer [SU]MIN, [SU]MAX, and ABS idioms, 213c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// returning the kind and providing the out parameter results if we 223c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// successfully match. 233c3b7f90a863af43fa63043d396553ecf205351cJohn McCallstatic SelectPatternFlavor 243c3b7f90a863af43fa63043d396553ecf205351cJohn McCallMatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) { 253c3b7f90a863af43fa63043d396553ecf205351cJohn McCall SelectInst *SI = dyn_cast<SelectInst>(V); 263c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (SI == 0) return SPF_UNKNOWN; 273c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 283c3b7f90a863af43fa63043d396553ecf205351cJohn McCall ICmpInst *ICI = dyn_cast<ICmpInst>(SI->getCondition()); 293c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (ICI == 0) return SPF_UNKNOWN; 303c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 313c3b7f90a863af43fa63043d396553ecf205351cJohn McCall LHS = ICI->getOperand(0); 323c3b7f90a863af43fa63043d396553ecf205351cJohn McCall RHS = ICI->getOperand(1); 333c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 343c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // (icmp X, Y) ? X : Y 353c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (SI->getTrueValue() == ICI->getOperand(0) && 363c3b7f90a863af43fa63043d396553ecf205351cJohn McCall SI->getFalseValue() == ICI->getOperand(1)) { 373c3b7f90a863af43fa63043d396553ecf205351cJohn McCall switch (ICI->getPredicate()) { 383c3b7f90a863af43fa63043d396553ecf205351cJohn McCall default: return SPF_UNKNOWN; // Equality. 393c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case ICmpInst::ICMP_UGT: 403c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case ICmpInst::ICMP_UGE: return SPF_UMAX; 413c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case ICmpInst::ICMP_SGT: 423c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case ICmpInst::ICMP_SGE: return SPF_SMAX; 433c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case ICmpInst::ICMP_ULT: 44aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer case ICmpInst::ICMP_ULE: return SPF_UMIN; 45aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer case ICmpInst::ICMP_SLT: 46aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer case ICmpInst::ICMP_SLE: return SPF_SMIN; 473c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 483c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 49aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer 50aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer // (icmp X, Y) ? Y : X 51aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer if (SI->getTrueValue() == ICI->getOperand(1) && 52aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer SI->getFalseValue() == ICI->getOperand(0)) { 53aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer switch (ICI->getPredicate()) { 54aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer default: return SPF_UNKNOWN; // Equality. 55aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer case ICmpInst::ICMP_UGT: 56aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer case ICmpInst::ICMP_UGE: return SPF_UMIN; 57aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer case ICmpInst::ICMP_SGT: 58aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer case ICmpInst::ICMP_SGE: return SPF_SMIN; 59aa9807a85959ffbdc5d9f649d7b24b9b2056d2cdBenjamin Kramer case ICmpInst::ICMP_ULT: 603c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case ICmpInst::ICMP_ULE: return SPF_UMAX; 613c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case ICmpInst::ICMP_SLT: 623c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case ICmpInst::ICMP_SLE: return SPF_SMAX; 633c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 643c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 653c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 663c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5) 673c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 683c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return SPF_UNKNOWN; 693c3b7f90a863af43fa63043d396553ecf205351cJohn McCall} 703c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 713c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 723c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// GetSelectFoldableOperands - We want to turn code that looks like this: 733c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// %C = or %A, %B 743c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// %D = select %cond, %C, %A 753c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// into: 763c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// %C = select %cond, %B, 0 773c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// %D = or %A, %C 783c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// 793c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// Assuming that the specified instruction is an operand to the select, return 803c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// a bitmask indicating which operands of this instruction are foldable if they 813c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// equal the other incoming value of the select. 823c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// 833c3b7f90a863af43fa63043d396553ecf205351cJohn McCallstatic unsigned GetSelectFoldableOperands(Instruction *I) { 843c3b7f90a863af43fa63043d396553ecf205351cJohn McCall switch (I->getOpcode()) { 853c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::Add: 863c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::Mul: 873c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::And: 883c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::Or: 893c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::Xor: 903c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return 3; // Can fold through either operand. 913c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::Sub: // Can only fold on the amount subtracted. 923c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::Shl: // Can only fold on the shift amount. 933c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::LShr: 943c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::AShr: 953c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return 1; 963c3b7f90a863af43fa63043d396553ecf205351cJohn McCall default: 973c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return 0; // Cannot fold 983c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 993c3b7f90a863af43fa63043d396553ecf205351cJohn McCall} 1003c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 1013c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// GetSelectFoldableConstant - For the same transformation as the previous 1023c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// function, return the identity constant that goes into the select. 1033c3b7f90a863af43fa63043d396553ecf205351cJohn McCallstatic Constant *GetSelectFoldableConstant(Instruction *I) { 1043c3b7f90a863af43fa63043d396553ecf205351cJohn McCall switch (I->getOpcode()) { 1053c3b7f90a863af43fa63043d396553ecf205351cJohn McCall default: llvm_unreachable("This cannot happen!"); 1063c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::Add: 1073c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::Sub: 1083c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::Or: 1093c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::Xor: 1103c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::Shl: 1113c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::LShr: 1123c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::AShr: 1133c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return Constant::getNullValue(I->getType()); 1143c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::And: 1153c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return Constant::getAllOnesValue(I->getType()); 1163c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case Instruction::Mul: 1173c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return ConstantInt::get(I->getType(), 1); 1183c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 1193c3b7f90a863af43fa63043d396553ecf205351cJohn McCall} 1203c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 1213c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI 1223c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// have the same opcode and only one use each. Try to simplify this. 1233c3b7f90a863af43fa63043d396553ecf205351cJohn McCallInstruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI, 1243c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Instruction *FI) { 1253c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (TI->getNumOperands() == 1) { 1263c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // If this is a non-volatile load or a cast from the same type, 1273c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // merge. 1283c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (TI->isCast()) { 1293c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (TI->getOperand(0)->getType() != FI->getOperand(0)->getType()) 1303c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return 0; 1313c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } else { 1323c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return 0; // unknown unary op. 1333c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 1343c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 1353c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // Fold this by inserting a select from the input values. 1363c3b7f90a863af43fa63043d396553ecf205351cJohn McCall SelectInst *NewSI = SelectInst::Create(SI.getCondition(), TI->getOperand(0), 1373c3b7f90a863af43fa63043d396553ecf205351cJohn McCall FI->getOperand(0), SI.getName()+".v"); 1383c3b7f90a863af43fa63043d396553ecf205351cJohn McCall InsertNewInstBefore(NewSI, SI); 1393c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI, 1403c3b7f90a863af43fa63043d396553ecf205351cJohn McCall TI->getType()); 1413c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 1423c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 1433c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // Only handle binary operators here. 1443c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (!isa<BinaryOperator>(TI)) 1453c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return 0; 1463c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 1473c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // Figure out if the operations have any operands in common. 1483c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Value *MatchOp, *OtherOpT, *OtherOpF; 1493c3b7f90a863af43fa63043d396553ecf205351cJohn McCall bool MatchIsOpZero; 1503c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (TI->getOperand(0) == FI->getOperand(0)) { 1513c3b7f90a863af43fa63043d396553ecf205351cJohn McCall MatchOp = TI->getOperand(0); 1523c3b7f90a863af43fa63043d396553ecf205351cJohn McCall OtherOpT = TI->getOperand(1); 1533c3b7f90a863af43fa63043d396553ecf205351cJohn McCall OtherOpF = FI->getOperand(1); 1543c3b7f90a863af43fa63043d396553ecf205351cJohn McCall MatchIsOpZero = true; 1553c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } else if (TI->getOperand(1) == FI->getOperand(1)) { 1563c3b7f90a863af43fa63043d396553ecf205351cJohn McCall MatchOp = TI->getOperand(1); 1573c3b7f90a863af43fa63043d396553ecf205351cJohn McCall OtherOpT = TI->getOperand(0); 1583c3b7f90a863af43fa63043d396553ecf205351cJohn McCall OtherOpF = FI->getOperand(0); 1593c3b7f90a863af43fa63043d396553ecf205351cJohn McCall MatchIsOpZero = false; 1603c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } else if (!TI->isCommutative()) { 1613c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return 0; 1623c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } else if (TI->getOperand(0) == FI->getOperand(1)) { 1633c3b7f90a863af43fa63043d396553ecf205351cJohn McCall MatchOp = TI->getOperand(0); 1643c3b7f90a863af43fa63043d396553ecf205351cJohn McCall OtherOpT = TI->getOperand(1); 1653c3b7f90a863af43fa63043d396553ecf205351cJohn McCall OtherOpF = FI->getOperand(0); 1663c3b7f90a863af43fa63043d396553ecf205351cJohn McCall MatchIsOpZero = true; 1673c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } else if (TI->getOperand(1) == FI->getOperand(0)) { 1683c3b7f90a863af43fa63043d396553ecf205351cJohn McCall MatchOp = TI->getOperand(1); 1693c3b7f90a863af43fa63043d396553ecf205351cJohn McCall OtherOpT = TI->getOperand(0); 1703c3b7f90a863af43fa63043d396553ecf205351cJohn McCall OtherOpF = FI->getOperand(1); 1713c3b7f90a863af43fa63043d396553ecf205351cJohn McCall MatchIsOpZero = true; 1723c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } else { 1733c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return 0; 1743c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 1753c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 1763c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // If we reach here, they do have operations in common. 1773c3b7f90a863af43fa63043d396553ecf205351cJohn McCall SelectInst *NewSI = SelectInst::Create(SI.getCondition(), OtherOpT, 1783c3b7f90a863af43fa63043d396553ecf205351cJohn McCall OtherOpF, SI.getName()+".v"); 1793c3b7f90a863af43fa63043d396553ecf205351cJohn McCall InsertNewInstBefore(NewSI, SI); 1803c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 1813c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) { 1823c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (MatchIsOpZero) 1833c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return BinaryOperator::Create(BO->getOpcode(), MatchOp, NewSI); 1843c3b7f90a863af43fa63043d396553ecf205351cJohn McCall else 1853c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return BinaryOperator::Create(BO->getOpcode(), NewSI, MatchOp); 1863c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 1873c3b7f90a863af43fa63043d396553ecf205351cJohn McCall llvm_unreachable("Shouldn't get here"); 1883c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return 0; 1893c3b7f90a863af43fa63043d396553ecf205351cJohn McCall} 1903c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 1913c3b7f90a863af43fa63043d396553ecf205351cJohn McCallstatic bool isSelect01(Constant *C1, Constant *C2) { 1923c3b7f90a863af43fa63043d396553ecf205351cJohn McCall ConstantInt *C1I = dyn_cast<ConstantInt>(C1); 1933c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (!C1I) 1943c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return false; 1953c3b7f90a863af43fa63043d396553ecf205351cJohn McCall ConstantInt *C2I = dyn_cast<ConstantInt>(C2); 1963c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (!C2I) 1973c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return false; 1983c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return (C1I->isZero() || C1I->isOne()) && (C2I->isZero() || C2I->isOne()); 1993c3b7f90a863af43fa63043d396553ecf205351cJohn McCall} 2003c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 2013c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// FoldSelectIntoOp - Try fold the select into one of the operands to 2023c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// facilitate further optimization. 2033c3b7f90a863af43fa63043d396553ecf205351cJohn McCallInstruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal, 2043c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Value *FalseVal) { 2053c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // See the comment above GetSelectFoldableOperands for a description of the 2063c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // transformation we are doing here. 2073c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (Instruction *TVI = dyn_cast<Instruction>(TrueVal)) { 2083c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (TVI->hasOneUse() && TVI->getNumOperands() == 2 && 2093c3b7f90a863af43fa63043d396553ecf205351cJohn McCall !isa<Constant>(FalseVal)) { 2103c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (unsigned SFO = GetSelectFoldableOperands(TVI)) { 2113c3b7f90a863af43fa63043d396553ecf205351cJohn McCall unsigned OpToFold = 0; 2123c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if ((SFO & 1) && FalseVal == TVI->getOperand(0)) { 2133c3b7f90a863af43fa63043d396553ecf205351cJohn McCall OpToFold = 1; 2143c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) { 2153c3b7f90a863af43fa63043d396553ecf205351cJohn McCall OpToFold = 2; 2163c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 2173c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 2183c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (OpToFold) { 2193c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Constant *C = GetSelectFoldableConstant(TVI); 2203c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Value *OOp = TVI->getOperand(2-OpToFold); 2213c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // Avoid creating select between 2 constants unless it's selecting 2223c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // between 0 and 1. 2233c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) { 2243c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Instruction *NewSel = SelectInst::Create(SI.getCondition(), OOp, C); 2253c3b7f90a863af43fa63043d396553ecf205351cJohn McCall InsertNewInstBefore(NewSel, SI); 2263c3b7f90a863af43fa63043d396553ecf205351cJohn McCall NewSel->takeName(TVI); 2273c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI)) 2283c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return BinaryOperator::Create(BO->getOpcode(), FalseVal, NewSel); 2293c3b7f90a863af43fa63043d396553ecf205351cJohn McCall llvm_unreachable("Unknown instruction!!"); 2303c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 2313c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 2323c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 2333c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 2343c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 2353c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 2363c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) { 2373c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (FVI->hasOneUse() && FVI->getNumOperands() == 2 && 2383c3b7f90a863af43fa63043d396553ecf205351cJohn McCall !isa<Constant>(TrueVal)) { 2393c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (unsigned SFO = GetSelectFoldableOperands(FVI)) { 2403c3b7f90a863af43fa63043d396553ecf205351cJohn McCall unsigned OpToFold = 0; 2413c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if ((SFO & 1) && TrueVal == FVI->getOperand(0)) { 2423c3b7f90a863af43fa63043d396553ecf205351cJohn McCall OpToFold = 1; 2433c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) { 2443c3b7f90a863af43fa63043d396553ecf205351cJohn McCall OpToFold = 2; 2453c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 2463c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 2473c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (OpToFold) { 2483c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Constant *C = GetSelectFoldableConstant(FVI); 2493c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Value *OOp = FVI->getOperand(2-OpToFold); 2503c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // Avoid creating select between 2 constants unless it's selecting 2513c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // between 0 and 1. 2523c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) { 2533c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Instruction *NewSel = SelectInst::Create(SI.getCondition(), C, OOp); 2543c3b7f90a863af43fa63043d396553ecf205351cJohn McCall InsertNewInstBefore(NewSel, SI); 2553c3b7f90a863af43fa63043d396553ecf205351cJohn McCall NewSel->takeName(FVI); 2563c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI)) 2573c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return BinaryOperator::Create(BO->getOpcode(), TrueVal, NewSel); 2583c3b7f90a863af43fa63043d396553ecf205351cJohn McCall llvm_unreachable("Unknown instruction!!"); 2593c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 2603c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 2613c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 2623c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 2633c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 2643c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 2653c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return 0; 2663c3b7f90a863af43fa63043d396553ecf205351cJohn McCall} 2673c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 2683c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// visitSelectInstWithICmp - Visit a SelectInst that has an 2693c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// ICmpInst as its first operand. 2703c3b7f90a863af43fa63043d396553ecf205351cJohn McCall/// 2713c3b7f90a863af43fa63043d396553ecf205351cJohn McCallInstruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI, 2723c3b7f90a863af43fa63043d396553ecf205351cJohn McCall ICmpInst *ICI) { 2733c3b7f90a863af43fa63043d396553ecf205351cJohn McCall bool Changed = false; 2743c3b7f90a863af43fa63043d396553ecf205351cJohn McCall ICmpInst::Predicate Pred = ICI->getPredicate(); 2753c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Value *CmpLHS = ICI->getOperand(0); 2763c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Value *CmpRHS = ICI->getOperand(1); 2773c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Value *TrueVal = SI.getTrueValue(); 2783c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Value *FalseVal = SI.getFalseValue(); 2793c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 2803c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // Check cases where the comparison is with a constant that 2813c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // can be adjusted to fit the min/max idiom. We may edit ICI in 2823c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // place here, so make sure the select is the only user. 2833c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (ICI->hasOneUse()) 2843c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) { 2853c3b7f90a863af43fa63043d396553ecf205351cJohn McCall switch (Pred) { 2863c3b7f90a863af43fa63043d396553ecf205351cJohn McCall default: break; 2873c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case ICmpInst::ICMP_ULT: 2883c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case ICmpInst::ICMP_SLT: { 2893c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // X < MIN ? T : F --> F 2903c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (CI->isMinValue(Pred == ICmpInst::ICMP_SLT)) 2913c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return ReplaceInstUsesWith(SI, FalseVal); 2923c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // X < C ? X : C-1 --> X > C-1 ? C-1 : X 2933c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Constant *AdjustedRHS = 2943c3b7f90a863af43fa63043d396553ecf205351cJohn McCall ConstantInt::get(CI->getContext(), CI->getValue()-1); 2953c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) || 2963c3b7f90a863af43fa63043d396553ecf205351cJohn McCall (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) { 2973c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Pred = ICmpInst::getSwappedPredicate(Pred); 2983c3b7f90a863af43fa63043d396553ecf205351cJohn McCall CmpRHS = AdjustedRHS; 2993c3b7f90a863af43fa63043d396553ecf205351cJohn McCall std::swap(FalseVal, TrueVal); 3003c3b7f90a863af43fa63043d396553ecf205351cJohn McCall ICI->setPredicate(Pred); 3013c3b7f90a863af43fa63043d396553ecf205351cJohn McCall ICI->setOperand(1, CmpRHS); 3023c3b7f90a863af43fa63043d396553ecf205351cJohn McCall SI.setOperand(1, TrueVal); 3033c3b7f90a863af43fa63043d396553ecf205351cJohn McCall SI.setOperand(2, FalseVal); 3043c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Changed = true; 3053c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 3063c3b7f90a863af43fa63043d396553ecf205351cJohn McCall break; 3073c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 3083c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case ICmpInst::ICMP_UGT: 3093c3b7f90a863af43fa63043d396553ecf205351cJohn McCall case ICmpInst::ICMP_SGT: { 3103c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // X > MAX ? T : F --> F 3113c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (CI->isMaxValue(Pred == ICmpInst::ICMP_SGT)) 3123c3b7f90a863af43fa63043d396553ecf205351cJohn McCall return ReplaceInstUsesWith(SI, FalseVal); 3133c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // X > C ? X : C+1 --> X < C+1 ? C+1 : X 3143c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Constant *AdjustedRHS = 3153c3b7f90a863af43fa63043d396553ecf205351cJohn McCall ConstantInt::get(CI->getContext(), CI->getValue()+1); 3163c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) || 3173c3b7f90a863af43fa63043d396553ecf205351cJohn McCall (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) { 3183c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Pred = ICmpInst::getSwappedPredicate(Pred); 3193c3b7f90a863af43fa63043d396553ecf205351cJohn McCall CmpRHS = AdjustedRHS; 3203c3b7f90a863af43fa63043d396553ecf205351cJohn McCall std::swap(FalseVal, TrueVal); 3213c3b7f90a863af43fa63043d396553ecf205351cJohn McCall ICI->setPredicate(Pred); 3223c3b7f90a863af43fa63043d396553ecf205351cJohn McCall ICI->setOperand(1, CmpRHS); 3233c3b7f90a863af43fa63043d396553ecf205351cJohn McCall SI.setOperand(1, TrueVal); 3243c3b7f90a863af43fa63043d396553ecf205351cJohn McCall SI.setOperand(2, FalseVal); 3253c3b7f90a863af43fa63043d396553ecf205351cJohn McCall Changed = true; 3263c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 3273c3b7f90a863af43fa63043d396553ecf205351cJohn McCall break; 3283c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 3293c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 3303c3b7f90a863af43fa63043d396553ecf205351cJohn McCall } 3313c3b7f90a863af43fa63043d396553ecf205351cJohn McCall 3323c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // Transform (X >s -1) ? C1 : C2 --> ((X >>s 31) & (C2 - C1)) + C1 3333c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // and (X <s 0) ? C2 : C1 --> ((X >>s 31) & (C2 - C1)) + C1 3343c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // FIXME: Type and constness constraints could be lifted, but we have to 3353c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // watch code size carefully. We should consider xor instead of 3363c3b7f90a863af43fa63043d396553ecf205351cJohn McCall // sub/add when we decide to do that. 3373c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (const IntegerType *Ty = dyn_cast<IntegerType>(CmpLHS->getType())) { 3383c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (TrueVal->getType() == Ty) { 3393c3b7f90a863af43fa63043d396553ecf205351cJohn McCall if (ConstantInt *Cmp = dyn_cast<ConstantInt>(CmpRHS)) { 340 ConstantInt *C1 = NULL, *C2 = NULL; 341 if (Pred == ICmpInst::ICMP_SGT && Cmp->isAllOnesValue()) { 342 C1 = dyn_cast<ConstantInt>(TrueVal); 343 C2 = dyn_cast<ConstantInt>(FalseVal); 344 } else if (Pred == ICmpInst::ICMP_SLT && Cmp->isNullValue()) { 345 C1 = dyn_cast<ConstantInt>(FalseVal); 346 C2 = dyn_cast<ConstantInt>(TrueVal); 347 } 348 if (C1 && C2) { 349 // This shift results in either -1 or 0. 350 Value *AShr = Builder->CreateAShr(CmpLHS, Ty->getBitWidth()-1); 351 352 // Check if we can express the operation with a single or. 353 if (C2->isAllOnesValue()) 354 return ReplaceInstUsesWith(SI, Builder->CreateOr(AShr, C1)); 355 356 Value *And = Builder->CreateAnd(AShr, C2->getValue()-C1->getValue()); 357 return ReplaceInstUsesWith(SI, Builder->CreateAdd(And, C1)); 358 } 359 } 360 } 361 } 362 363 if (CmpLHS == TrueVal && CmpRHS == FalseVal) { 364 // Transform (X == Y) ? X : Y -> Y 365 if (Pred == ICmpInst::ICMP_EQ) 366 return ReplaceInstUsesWith(SI, FalseVal); 367 // Transform (X != Y) ? X : Y -> X 368 if (Pred == ICmpInst::ICMP_NE) 369 return ReplaceInstUsesWith(SI, TrueVal); 370 /// NOTE: if we wanted to, this is where to detect integer MIN/MAX 371 372 } else if (CmpLHS == FalseVal && CmpRHS == TrueVal) { 373 // Transform (X == Y) ? Y : X -> X 374 if (Pred == ICmpInst::ICMP_EQ) 375 return ReplaceInstUsesWith(SI, FalseVal); 376 // Transform (X != Y) ? Y : X -> Y 377 if (Pred == ICmpInst::ICMP_NE) 378 return ReplaceInstUsesWith(SI, TrueVal); 379 /// NOTE: if we wanted to, this is where to detect integer MIN/MAX 380 } 381 return Changed ? &SI : 0; 382} 383 384 385/// CanSelectOperandBeMappingIntoPredBlock - SI is a select whose condition is a 386/// PHI node (but the two may be in different blocks). See if the true/false 387/// values (V) are live in all of the predecessor blocks of the PHI. For 388/// example, cases like this cannot be mapped: 389/// 390/// X = phi [ C1, BB1], [C2, BB2] 391/// Y = add 392/// Z = select X, Y, 0 393/// 394/// because Y is not live in BB1/BB2. 395/// 396static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V, 397 const SelectInst &SI) { 398 // If the value is a non-instruction value like a constant or argument, it 399 // can always be mapped. 400 const Instruction *I = dyn_cast<Instruction>(V); 401 if (I == 0) return true; 402 403 // If V is a PHI node defined in the same block as the condition PHI, we can 404 // map the arguments. 405 const PHINode *CondPHI = cast<PHINode>(SI.getCondition()); 406 407 if (const PHINode *VP = dyn_cast<PHINode>(I)) 408 if (VP->getParent() == CondPHI->getParent()) 409 return true; 410 411 // Otherwise, if the PHI and select are defined in the same block and if V is 412 // defined in a different block, then we can transform it. 413 if (SI.getParent() == CondPHI->getParent() && 414 I->getParent() != CondPHI->getParent()) 415 return true; 416 417 // Otherwise we have a 'hard' case and we can't tell without doing more 418 // detailed dominator based analysis, punt. 419 return false; 420} 421 422/// FoldSPFofSPF - We have an SPF (e.g. a min or max) of an SPF of the form: 423/// SPF2(SPF1(A, B), C) 424Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner, 425 SelectPatternFlavor SPF1, 426 Value *A, Value *B, 427 Instruction &Outer, 428 SelectPatternFlavor SPF2, Value *C) { 429 if (C == A || C == B) { 430 // MAX(MAX(A, B), B) -> MAX(A, B) 431 // MIN(MIN(a, b), a) -> MIN(a, b) 432 if (SPF1 == SPF2) 433 return ReplaceInstUsesWith(Outer, Inner); 434 435 // MAX(MIN(a, b), a) -> a 436 // MIN(MAX(a, b), a) -> a 437 if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) || 438 (SPF1 == SPF_SMAX && SPF2 == SPF_SMIN) || 439 (SPF1 == SPF_UMIN && SPF2 == SPF_UMAX) || 440 (SPF1 == SPF_UMAX && SPF2 == SPF_UMIN)) 441 return ReplaceInstUsesWith(Outer, C); 442 } 443 444 // TODO: MIN(MIN(A, 23), 97) 445 return 0; 446} 447 448 449 450 451Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { 452 Value *CondVal = SI.getCondition(); 453 Value *TrueVal = SI.getTrueValue(); 454 Value *FalseVal = SI.getFalseValue(); 455 456 if (Value *V = SimplifySelectInst(CondVal, TrueVal, FalseVal, TD)) 457 return ReplaceInstUsesWith(SI, V); 458 459 if (SI.getType()->isIntegerTy(1)) { 460 if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) { 461 if (C->getZExtValue()) { 462 // Change: A = select B, true, C --> A = or B, C 463 return BinaryOperator::CreateOr(CondVal, FalseVal); 464 } 465 // Change: A = select B, false, C --> A = and !B, C 466 Value *NotCond = 467 InsertNewInstBefore(BinaryOperator::CreateNot(CondVal, 468 "not."+CondVal->getName()), SI); 469 return BinaryOperator::CreateAnd(NotCond, FalseVal); 470 } else if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) { 471 if (C->getZExtValue() == false) { 472 // Change: A = select B, C, false --> A = and B, C 473 return BinaryOperator::CreateAnd(CondVal, TrueVal); 474 } 475 // Change: A = select B, C, true --> A = or !B, C 476 Value *NotCond = 477 InsertNewInstBefore(BinaryOperator::CreateNot(CondVal, 478 "not."+CondVal->getName()), SI); 479 return BinaryOperator::CreateOr(NotCond, TrueVal); 480 } 481 482 // select a, b, a -> a&b 483 // select a, a, b -> a|b 484 if (CondVal == TrueVal) 485 return BinaryOperator::CreateOr(CondVal, FalseVal); 486 else if (CondVal == FalseVal) 487 return BinaryOperator::CreateAnd(CondVal, TrueVal); 488 } 489 490 // Selecting between two integer constants? 491 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal)) 492 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) { 493 // select C, 1, 0 -> zext C to int 494 if (FalseValC->isZero() && TrueValC->getValue() == 1) 495 return new ZExtInst(CondVal, SI.getType()); 496 497 // select C, -1, 0 -> sext C to int 498 if (FalseValC->isZero() && TrueValC->isAllOnesValue()) 499 return new SExtInst(CondVal, SI.getType()); 500 501 // select C, 0, 1 -> zext !C to int 502 if (TrueValC->isZero() && FalseValC->getValue() == 1) { 503 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName()); 504 return new ZExtInst(NotCond, SI.getType()); 505 } 506 507 // select C, 0, -1 -> sext !C to int 508 if (TrueValC->isZero() && FalseValC->isAllOnesValue()) { 509 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName()); 510 return new SExtInst(NotCond, SI.getType()); 511 } 512 513 if (ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition())) { 514 // If one of the constants is zero (we know they can't both be) and we 515 // have an icmp instruction with zero, and we have an 'and' with the 516 // non-constant value, eliminate this whole mess. This corresponds to 517 // cases like this: ((X & 27) ? 27 : 0) 518 if (TrueValC->isZero() || FalseValC->isZero()) 519 if (IC->isEquality() && isa<ConstantInt>(IC->getOperand(1)) && 520 cast<Constant>(IC->getOperand(1))->isNullValue()) 521 if (Instruction *ICA = dyn_cast<Instruction>(IC->getOperand(0))) 522 if (ICA->getOpcode() == Instruction::And && 523 isa<ConstantInt>(ICA->getOperand(1)) && 524 (ICA->getOperand(1) == TrueValC || 525 ICA->getOperand(1) == FalseValC) && 526 cast<ConstantInt>(ICA->getOperand(1))->getValue().isPowerOf2()) { 527 // Okay, now we know that everything is set up, we just don't 528 // know whether we have a icmp_ne or icmp_eq and whether the 529 // true or false val is the zero. 530 bool ShouldNotVal = !TrueValC->isZero(); 531 ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE; 532 Value *V = ICA; 533 if (ShouldNotVal) 534 V = Builder->CreateXor(V, ICA->getOperand(1)); 535 return ReplaceInstUsesWith(SI, V); 536 } 537 } 538 } 539 540 // See if we are selecting two values based on a comparison of the two values. 541 if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) { 542 if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) { 543 // Transform (X == Y) ? X : Y -> Y 544 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) { 545 // This is not safe in general for floating point: 546 // consider X== -0, Y== +0. 547 // It becomes safe if either operand is a nonzero constant. 548 ConstantFP *CFPt, *CFPf; 549 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && 550 !CFPt->getValueAPF().isZero()) || 551 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && 552 !CFPf->getValueAPF().isZero())) 553 return ReplaceInstUsesWith(SI, FalseVal); 554 } 555 // Transform (X une Y) ? X : Y -> X 556 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) { 557 // This is not safe in general for floating point: 558 // consider X== -0, Y== +0. 559 // It becomes safe if either operand is a nonzero constant. 560 ConstantFP *CFPt, *CFPf; 561 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && 562 !CFPt->getValueAPF().isZero()) || 563 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && 564 !CFPf->getValueAPF().isZero())) 565 return ReplaceInstUsesWith(SI, TrueVal); 566 } 567 // NOTE: if we wanted to, this is where to detect MIN/MAX 568 569 } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){ 570 // Transform (X == Y) ? Y : X -> X 571 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) { 572 // This is not safe in general for floating point: 573 // consider X== -0, Y== +0. 574 // It becomes safe if either operand is a nonzero constant. 575 ConstantFP *CFPt, *CFPf; 576 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && 577 !CFPt->getValueAPF().isZero()) || 578 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && 579 !CFPf->getValueAPF().isZero())) 580 return ReplaceInstUsesWith(SI, FalseVal); 581 } 582 // Transform (X une Y) ? Y : X -> Y 583 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) { 584 // This is not safe in general for floating point: 585 // consider X== -0, Y== +0. 586 // It becomes safe if either operand is a nonzero constant. 587 ConstantFP *CFPt, *CFPf; 588 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && 589 !CFPt->getValueAPF().isZero()) || 590 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && 591 !CFPf->getValueAPF().isZero())) 592 return ReplaceInstUsesWith(SI, TrueVal); 593 } 594 // NOTE: if we wanted to, this is where to detect MIN/MAX 595 } 596 // NOTE: if we wanted to, this is where to detect ABS 597 } 598 599 // See if we are selecting two values based on a comparison of the two values. 600 if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal)) 601 if (Instruction *Result = visitSelectInstWithICmp(SI, ICI)) 602 return Result; 603 604 if (Instruction *TI = dyn_cast<Instruction>(TrueVal)) 605 if (Instruction *FI = dyn_cast<Instruction>(FalseVal)) 606 if (TI->hasOneUse() && FI->hasOneUse()) { 607 Instruction *AddOp = 0, *SubOp = 0; 608 609 // Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z)) 610 if (TI->getOpcode() == FI->getOpcode()) 611 if (Instruction *IV = FoldSelectOpOp(SI, TI, FI)) 612 return IV; 613 614 // Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is 615 // even legal for FP. 616 if ((TI->getOpcode() == Instruction::Sub && 617 FI->getOpcode() == Instruction::Add) || 618 (TI->getOpcode() == Instruction::FSub && 619 FI->getOpcode() == Instruction::FAdd)) { 620 AddOp = FI; SubOp = TI; 621 } else if ((FI->getOpcode() == Instruction::Sub && 622 TI->getOpcode() == Instruction::Add) || 623 (FI->getOpcode() == Instruction::FSub && 624 TI->getOpcode() == Instruction::FAdd)) { 625 AddOp = TI; SubOp = FI; 626 } 627 628 if (AddOp) { 629 Value *OtherAddOp = 0; 630 if (SubOp->getOperand(0) == AddOp->getOperand(0)) { 631 OtherAddOp = AddOp->getOperand(1); 632 } else if (SubOp->getOperand(0) == AddOp->getOperand(1)) { 633 OtherAddOp = AddOp->getOperand(0); 634 } 635 636 if (OtherAddOp) { 637 // So at this point we know we have (Y -> OtherAddOp): 638 // select C, (add X, Y), (sub X, Z) 639 Value *NegVal; // Compute -Z 640 if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) { 641 NegVal = ConstantExpr::getNeg(C); 642 } else { 643 NegVal = InsertNewInstBefore( 644 BinaryOperator::CreateNeg(SubOp->getOperand(1), 645 "tmp"), SI); 646 } 647 648 Value *NewTrueOp = OtherAddOp; 649 Value *NewFalseOp = NegVal; 650 if (AddOp != TI) 651 std::swap(NewTrueOp, NewFalseOp); 652 Instruction *NewSel = 653 SelectInst::Create(CondVal, NewTrueOp, 654 NewFalseOp, SI.getName() + ".p"); 655 656 NewSel = InsertNewInstBefore(NewSel, SI); 657 return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel); 658 } 659 } 660 } 661 662 // See if we can fold the select into one of our operands. 663 if (SI.getType()->isIntegerTy()) { 664 if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal)) 665 return FoldI; 666 667 // MAX(MAX(a, b), a) -> MAX(a, b) 668 // MIN(MIN(a, b), a) -> MIN(a, b) 669 // MAX(MIN(a, b), a) -> a 670 // MIN(MAX(a, b), a) -> a 671 Value *LHS, *RHS, *LHS2, *RHS2; 672 if (SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS)) { 673 if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2)) 674 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2, 675 SI, SPF, RHS)) 676 return R; 677 if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2)) 678 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2, 679 SI, SPF, LHS)) 680 return R; 681 } 682 683 // TODO. 684 // ABS(-X) -> ABS(X) 685 // ABS(ABS(X)) -> ABS(X) 686 } 687 688 // See if we can fold the select into a phi node if the condition is a select. 689 if (isa<PHINode>(SI.getCondition())) 690 // The true/false values have to be live in the PHI predecessor's blocks. 691 if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) && 692 CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI)) 693 if (Instruction *NV = FoldOpIntoPhi(SI)) 694 return NV; 695 696 if (BinaryOperator::isNot(CondVal)) { 697 SI.setOperand(0, BinaryOperator::getNotArgument(CondVal)); 698 SI.setOperand(1, FalseVal); 699 SI.setOperand(2, TrueVal); 700 return &SI; 701 } 702 703 return 0; 704} 705