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https://github.com/c64scene-ar/llvm-6502.git
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df3bfae151
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124469 91177308-0d34-0410-b5e6-96231b3b80d8
817 lines
31 KiB
C++
817 lines
31 KiB
C++
//===- InstCombineSelect.cpp ----------------------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the visitSelect function.
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//
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//===----------------------------------------------------------------------===//
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#include "InstCombine.h"
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#include "llvm/Support/PatternMatch.h"
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#include "llvm/Analysis/InstructionSimplify.h"
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using namespace llvm;
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using namespace PatternMatch;
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/// MatchSelectPattern - Pattern match integer [SU]MIN, [SU]MAX, and ABS idioms,
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/// returning the kind and providing the out parameter results if we
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/// successfully match.
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static SelectPatternFlavor
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MatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) {
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SelectInst *SI = dyn_cast<SelectInst>(V);
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if (SI == 0) return SPF_UNKNOWN;
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ICmpInst *ICI = dyn_cast<ICmpInst>(SI->getCondition());
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if (ICI == 0) return SPF_UNKNOWN;
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LHS = ICI->getOperand(0);
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RHS = ICI->getOperand(1);
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// (icmp X, Y) ? X : Y
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if (SI->getTrueValue() == ICI->getOperand(0) &&
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SI->getFalseValue() == ICI->getOperand(1)) {
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switch (ICI->getPredicate()) {
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default: return SPF_UNKNOWN; // Equality.
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case ICmpInst::ICMP_UGT:
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case ICmpInst::ICMP_UGE: return SPF_UMAX;
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case ICmpInst::ICMP_SGT:
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case ICmpInst::ICMP_SGE: return SPF_SMAX;
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case ICmpInst::ICMP_ULT:
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case ICmpInst::ICMP_ULE: return SPF_UMIN;
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case ICmpInst::ICMP_SLT:
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case ICmpInst::ICMP_SLE: return SPF_SMIN;
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}
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}
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// (icmp X, Y) ? Y : X
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if (SI->getTrueValue() == ICI->getOperand(1) &&
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SI->getFalseValue() == ICI->getOperand(0)) {
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switch (ICI->getPredicate()) {
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default: return SPF_UNKNOWN; // Equality.
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case ICmpInst::ICMP_UGT:
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case ICmpInst::ICMP_UGE: return SPF_UMIN;
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case ICmpInst::ICMP_SGT:
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case ICmpInst::ICMP_SGE: return SPF_SMIN;
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case ICmpInst::ICMP_ULT:
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case ICmpInst::ICMP_ULE: return SPF_UMAX;
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case ICmpInst::ICMP_SLT:
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case ICmpInst::ICMP_SLE: return SPF_SMAX;
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}
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}
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// TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5)
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return SPF_UNKNOWN;
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}
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/// GetSelectFoldableOperands - We want to turn code that looks like this:
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/// %C = or %A, %B
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/// %D = select %cond, %C, %A
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/// into:
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/// %C = select %cond, %B, 0
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/// %D = or %A, %C
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///
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/// Assuming that the specified instruction is an operand to the select, return
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/// a bitmask indicating which operands of this instruction are foldable if they
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/// equal the other incoming value of the select.
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///
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static unsigned GetSelectFoldableOperands(Instruction *I) {
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switch (I->getOpcode()) {
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case Instruction::Add:
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case Instruction::Mul:
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case Instruction::And:
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case Instruction::Or:
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case Instruction::Xor:
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return 3; // Can fold through either operand.
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case Instruction::Sub: // Can only fold on the amount subtracted.
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case Instruction::Shl: // Can only fold on the shift amount.
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case Instruction::LShr:
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case Instruction::AShr:
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return 1;
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default:
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return 0; // Cannot fold
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}
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}
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/// GetSelectFoldableConstant - For the same transformation as the previous
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/// function, return the identity constant that goes into the select.
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static Constant *GetSelectFoldableConstant(Instruction *I) {
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switch (I->getOpcode()) {
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default: llvm_unreachable("This cannot happen!");
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case Instruction::Add:
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case Instruction::Sub:
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case Instruction::Or:
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case Instruction::Xor:
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case Instruction::Shl:
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case Instruction::LShr:
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case Instruction::AShr:
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return Constant::getNullValue(I->getType());
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case Instruction::And:
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return Constant::getAllOnesValue(I->getType());
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case Instruction::Mul:
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return ConstantInt::get(I->getType(), 1);
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}
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}
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/// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI
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/// have the same opcode and only one use each. Try to simplify this.
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Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI,
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Instruction *FI) {
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if (TI->getNumOperands() == 1) {
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// If this is a non-volatile load or a cast from the same type,
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// merge.
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if (TI->isCast()) {
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if (TI->getOperand(0)->getType() != FI->getOperand(0)->getType())
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return 0;
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} else {
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return 0; // unknown unary op.
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}
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// Fold this by inserting a select from the input values.
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SelectInst *NewSI = SelectInst::Create(SI.getCondition(), TI->getOperand(0),
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FI->getOperand(0), SI.getName()+".v");
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InsertNewInstBefore(NewSI, SI);
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return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI,
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TI->getType());
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}
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// Only handle binary operators here.
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if (!isa<BinaryOperator>(TI))
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return 0;
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// Figure out if the operations have any operands in common.
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Value *MatchOp, *OtherOpT, *OtherOpF;
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bool MatchIsOpZero;
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if (TI->getOperand(0) == FI->getOperand(0)) {
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MatchOp = TI->getOperand(0);
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OtherOpT = TI->getOperand(1);
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OtherOpF = FI->getOperand(1);
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MatchIsOpZero = true;
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} else if (TI->getOperand(1) == FI->getOperand(1)) {
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MatchOp = TI->getOperand(1);
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OtherOpT = TI->getOperand(0);
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OtherOpF = FI->getOperand(0);
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MatchIsOpZero = false;
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} else if (!TI->isCommutative()) {
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return 0;
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} else if (TI->getOperand(0) == FI->getOperand(1)) {
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MatchOp = TI->getOperand(0);
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OtherOpT = TI->getOperand(1);
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OtherOpF = FI->getOperand(0);
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MatchIsOpZero = true;
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} else if (TI->getOperand(1) == FI->getOperand(0)) {
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MatchOp = TI->getOperand(1);
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OtherOpT = TI->getOperand(0);
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OtherOpF = FI->getOperand(1);
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MatchIsOpZero = true;
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} else {
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return 0;
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}
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// If we reach here, they do have operations in common.
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SelectInst *NewSI = SelectInst::Create(SI.getCondition(), OtherOpT,
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OtherOpF, SI.getName()+".v");
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InsertNewInstBefore(NewSI, SI);
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if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) {
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if (MatchIsOpZero)
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return BinaryOperator::Create(BO->getOpcode(), MatchOp, NewSI);
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else
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return BinaryOperator::Create(BO->getOpcode(), NewSI, MatchOp);
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}
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llvm_unreachable("Shouldn't get here");
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return 0;
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}
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static bool isSelect01(Constant *C1, Constant *C2) {
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ConstantInt *C1I = dyn_cast<ConstantInt>(C1);
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if (!C1I)
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return false;
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ConstantInt *C2I = dyn_cast<ConstantInt>(C2);
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if (!C2I)
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return false;
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if (!C1I->isZero() && !C2I->isZero()) // One side must be zero.
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return false;
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return C1I->isOne() || C1I->isAllOnesValue() ||
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C2I->isOne() || C2I->isAllOnesValue();
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}
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/// FoldSelectIntoOp - Try fold the select into one of the operands to
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/// facilitate further optimization.
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Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal,
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Value *FalseVal) {
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// See the comment above GetSelectFoldableOperands for a description of the
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// transformation we are doing here.
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if (Instruction *TVI = dyn_cast<Instruction>(TrueVal)) {
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if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
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!isa<Constant>(FalseVal)) {
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if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
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unsigned OpToFold = 0;
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if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
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OpToFold = 1;
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} else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
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OpToFold = 2;
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}
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if (OpToFold) {
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Constant *C = GetSelectFoldableConstant(TVI);
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Value *OOp = TVI->getOperand(2-OpToFold);
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// Avoid creating select between 2 constants unless it's selecting
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// between 0, 1 and -1.
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if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
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Instruction *NewSel = SelectInst::Create(SI.getCondition(), OOp, C);
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InsertNewInstBefore(NewSel, SI);
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NewSel->takeName(TVI);
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if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
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return BinaryOperator::Create(BO->getOpcode(), FalseVal, NewSel);
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llvm_unreachable("Unknown instruction!!");
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}
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}
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}
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}
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}
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if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) {
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if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
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!isa<Constant>(TrueVal)) {
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if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
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unsigned OpToFold = 0;
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if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
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OpToFold = 1;
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} else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
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OpToFold = 2;
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}
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if (OpToFold) {
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Constant *C = GetSelectFoldableConstant(FVI);
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Value *OOp = FVI->getOperand(2-OpToFold);
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// Avoid creating select between 2 constants unless it's selecting
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// between 0, 1 and -1.
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if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
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Instruction *NewSel = SelectInst::Create(SI.getCondition(), C, OOp);
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InsertNewInstBefore(NewSel, SI);
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NewSel->takeName(FVI);
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if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
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return BinaryOperator::Create(BO->getOpcode(), TrueVal, NewSel);
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llvm_unreachable("Unknown instruction!!");
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}
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}
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}
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}
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}
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return 0;
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}
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/// visitSelectInstWithICmp - Visit a SelectInst that has an
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/// ICmpInst as its first operand.
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///
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Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
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ICmpInst *ICI) {
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bool Changed = false;
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ICmpInst::Predicate Pred = ICI->getPredicate();
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Value *CmpLHS = ICI->getOperand(0);
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Value *CmpRHS = ICI->getOperand(1);
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Value *TrueVal = SI.getTrueValue();
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Value *FalseVal = SI.getFalseValue();
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// Check cases where the comparison is with a constant that
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// can be adjusted to fit the min/max idiom. We may move or edit ICI
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// here, so make sure the select is the only user.
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if (ICI->hasOneUse())
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if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) {
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// X < MIN ? T : F --> F
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if ((Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_ULT)
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&& CI->isMinValue(Pred == ICmpInst::ICMP_SLT))
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return ReplaceInstUsesWith(SI, FalseVal);
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// X > MAX ? T : F --> F
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else if ((Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_UGT)
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&& CI->isMaxValue(Pred == ICmpInst::ICMP_SGT))
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return ReplaceInstUsesWith(SI, FalseVal);
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switch (Pred) {
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default: break;
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case ICmpInst::ICMP_ULT:
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case ICmpInst::ICMP_SLT:
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case ICmpInst::ICMP_UGT:
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case ICmpInst::ICMP_SGT: {
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// These transformations only work for selects over integers.
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const IntegerType *SelectTy = dyn_cast<IntegerType>(SI.getType());
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if (!SelectTy)
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break;
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Constant *AdjustedRHS;
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if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_SGT)
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AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() + 1);
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else // (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_SLT)
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AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() - 1);
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// X > C ? X : C+1 --> X < C+1 ? C+1 : X
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// X < C ? X : C-1 --> X > C-1 ? C-1 : X
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if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
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(CmpLHS == FalseVal && AdjustedRHS == TrueVal))
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; // Nothing to do here. Values match without any sign/zero extension.
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// Types do not match. Instead of calculating this with mixed types
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// promote all to the larger type. This enables scalar evolution to
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// analyze this expression.
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else if (CmpRHS->getType()->getScalarSizeInBits()
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< SelectTy->getBitWidth()) {
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Constant *sextRHS = ConstantExpr::getSExt(AdjustedRHS, SelectTy);
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// X = sext x; x >s c ? X : C+1 --> X = sext x; X <s C+1 ? C+1 : X
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// X = sext x; x <s c ? X : C-1 --> X = sext x; X >s C-1 ? C-1 : X
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// X = sext x; x >u c ? X : C+1 --> X = sext x; X <u C+1 ? C+1 : X
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// X = sext x; x <u c ? X : C-1 --> X = sext x; X >u C-1 ? C-1 : X
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if (match(TrueVal, m_SExt(m_Specific(CmpLHS))) &&
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sextRHS == FalseVal) {
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CmpLHS = TrueVal;
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AdjustedRHS = sextRHS;
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} else if (match(FalseVal, m_SExt(m_Specific(CmpLHS))) &&
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sextRHS == TrueVal) {
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CmpLHS = FalseVal;
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AdjustedRHS = sextRHS;
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} else if (ICI->isUnsigned()) {
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Constant *zextRHS = ConstantExpr::getZExt(AdjustedRHS, SelectTy);
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// X = zext x; x >u c ? X : C+1 --> X = zext x; X <u C+1 ? C+1 : X
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// X = zext x; x <u c ? X : C-1 --> X = zext x; X >u C-1 ? C-1 : X
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// zext + signed compare cannot be changed:
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// 0xff <s 0x00, but 0x00ff >s 0x0000
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if (match(TrueVal, m_ZExt(m_Specific(CmpLHS))) &&
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zextRHS == FalseVal) {
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CmpLHS = TrueVal;
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AdjustedRHS = zextRHS;
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} else if (match(FalseVal, m_ZExt(m_Specific(CmpLHS))) &&
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zextRHS == TrueVal) {
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CmpLHS = FalseVal;
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AdjustedRHS = zextRHS;
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} else
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break;
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} else
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break;
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} else
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break;
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Pred = ICmpInst::getSwappedPredicate(Pred);
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CmpRHS = AdjustedRHS;
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std::swap(FalseVal, TrueVal);
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ICI->setPredicate(Pred);
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ICI->setOperand(0, CmpLHS);
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ICI->setOperand(1, CmpRHS);
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SI.setOperand(1, TrueVal);
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SI.setOperand(2, FalseVal);
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// Move ICI instruction right before the select instruction. Otherwise
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// the sext/zext value may be defined after the ICI instruction uses it.
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ICI->moveBefore(&SI);
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Changed = true;
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break;
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}
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}
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}
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// Transform (X >s -1) ? C1 : C2 --> ((X >>s 31) & (C2 - C1)) + C1
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// and (X <s 0) ? C2 : C1 --> ((X >>s 31) & (C2 - C1)) + C1
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// FIXME: Type and constness constraints could be lifted, but we have to
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// watch code size carefully. We should consider xor instead of
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// sub/add when we decide to do that.
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if (const IntegerType *Ty = dyn_cast<IntegerType>(CmpLHS->getType())) {
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if (TrueVal->getType() == Ty) {
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if (ConstantInt *Cmp = dyn_cast<ConstantInt>(CmpRHS)) {
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ConstantInt *C1 = NULL, *C2 = NULL;
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if (Pred == ICmpInst::ICMP_SGT && Cmp->isAllOnesValue()) {
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C1 = dyn_cast<ConstantInt>(TrueVal);
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C2 = dyn_cast<ConstantInt>(FalseVal);
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} else if (Pred == ICmpInst::ICMP_SLT && Cmp->isNullValue()) {
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C1 = dyn_cast<ConstantInt>(FalseVal);
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C2 = dyn_cast<ConstantInt>(TrueVal);
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}
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if (C1 && C2) {
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// This shift results in either -1 or 0.
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Value *AShr = Builder->CreateAShr(CmpLHS, Ty->getBitWidth()-1);
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// Check if we can express the operation with a single or.
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if (C2->isAllOnesValue())
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return ReplaceInstUsesWith(SI, Builder->CreateOr(AShr, C1));
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Value *And = Builder->CreateAnd(AShr, C2->getValue()-C1->getValue());
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return ReplaceInstUsesWith(SI, Builder->CreateAdd(And, C1));
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}
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}
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}
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}
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if (CmpLHS == TrueVal && CmpRHS == FalseVal) {
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// Transform (X == Y) ? X : Y -> Y
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if (Pred == ICmpInst::ICMP_EQ)
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return ReplaceInstUsesWith(SI, FalseVal);
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// Transform (X != Y) ? X : Y -> X
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if (Pred == ICmpInst::ICMP_NE)
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return ReplaceInstUsesWith(SI, TrueVal);
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/// NOTE: if we wanted to, this is where to detect integer MIN/MAX
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} else if (CmpLHS == FalseVal && CmpRHS == TrueVal) {
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// Transform (X == Y) ? Y : X -> X
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if (Pred == ICmpInst::ICMP_EQ)
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return ReplaceInstUsesWith(SI, FalseVal);
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// Transform (X != Y) ? Y : X -> Y
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if (Pred == ICmpInst::ICMP_NE)
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return ReplaceInstUsesWith(SI, TrueVal);
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/// NOTE: if we wanted to, this is where to detect integer MIN/MAX
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}
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return Changed ? &SI : 0;
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}
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/// CanSelectOperandBeMappingIntoPredBlock - SI is a select whose condition is a
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/// PHI node (but the two may be in different blocks). See if the true/false
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/// values (V) are live in all of the predecessor blocks of the PHI. For
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/// example, cases like this cannot be mapped:
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///
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/// X = phi [ C1, BB1], [C2, BB2]
|
|
/// Y = add
|
|
/// Z = select X, Y, 0
|
|
///
|
|
/// because Y is not live in BB1/BB2.
|
|
///
|
|
static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V,
|
|
const SelectInst &SI) {
|
|
// If the value is a non-instruction value like a constant or argument, it
|
|
// can always be mapped.
|
|
const Instruction *I = dyn_cast<Instruction>(V);
|
|
if (I == 0) return true;
|
|
|
|
// If V is a PHI node defined in the same block as the condition PHI, we can
|
|
// map the arguments.
|
|
const PHINode *CondPHI = cast<PHINode>(SI.getCondition());
|
|
|
|
if (const PHINode *VP = dyn_cast<PHINode>(I))
|
|
if (VP->getParent() == CondPHI->getParent())
|
|
return true;
|
|
|
|
// Otherwise, if the PHI and select are defined in the same block and if V is
|
|
// defined in a different block, then we can transform it.
|
|
if (SI.getParent() == CondPHI->getParent() &&
|
|
I->getParent() != CondPHI->getParent())
|
|
return true;
|
|
|
|
// Otherwise we have a 'hard' case and we can't tell without doing more
|
|
// detailed dominator based analysis, punt.
|
|
return false;
|
|
}
|
|
|
|
/// FoldSPFofSPF - We have an SPF (e.g. a min or max) of an SPF of the form:
|
|
/// SPF2(SPF1(A, B), C)
|
|
Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner,
|
|
SelectPatternFlavor SPF1,
|
|
Value *A, Value *B,
|
|
Instruction &Outer,
|
|
SelectPatternFlavor SPF2, Value *C) {
|
|
if (C == A || C == B) {
|
|
// MAX(MAX(A, B), B) -> MAX(A, B)
|
|
// MIN(MIN(a, b), a) -> MIN(a, b)
|
|
if (SPF1 == SPF2)
|
|
return ReplaceInstUsesWith(Outer, Inner);
|
|
|
|
// MAX(MIN(a, b), a) -> a
|
|
// MIN(MAX(a, b), a) -> a
|
|
if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) ||
|
|
(SPF1 == SPF_SMAX && SPF2 == SPF_SMIN) ||
|
|
(SPF1 == SPF_UMIN && SPF2 == SPF_UMAX) ||
|
|
(SPF1 == SPF_UMAX && SPF2 == SPF_UMIN))
|
|
return ReplaceInstUsesWith(Outer, C);
|
|
}
|
|
|
|
// TODO: MIN(MIN(A, 23), 97)
|
|
return 0;
|
|
}
|
|
|
|
|
|
/// foldSelectICmpAnd - If one of the constants is zero (we know they can't
|
|
/// both be) and we have an icmp instruction with zero, and we have an 'and'
|
|
/// with the non-constant value and a power of two we can turn the select
|
|
/// into a shift on the result of the 'and'.
|
|
static Value *foldSelectICmpAnd(const SelectInst &SI, ConstantInt *TrueVal,
|
|
ConstantInt *FalseVal,
|
|
InstCombiner::BuilderTy *Builder) {
|
|
const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
|
|
if (!IC || !IC->isEquality())
|
|
return 0;
|
|
|
|
if (ConstantInt *C = dyn_cast<ConstantInt>(IC->getOperand(1)))
|
|
if (!C->isZero())
|
|
return 0;
|
|
|
|
ConstantInt *AndRHS;
|
|
Value *LHS = IC->getOperand(0);
|
|
if (LHS->getType() != SI.getType() ||
|
|
!match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS))))
|
|
return 0;
|
|
|
|
// If both select arms are non-zero see if we have a select of the form
|
|
// 'x ? 2^n + C : C'. Then we can offset both arms by C, use the logic
|
|
// for 'x ? 2^n : 0' and fix the thing up at the end.
|
|
ConstantInt *Offset = 0;
|
|
if (!TrueVal->isZero() && !FalseVal->isZero()) {
|
|
if ((TrueVal->getValue() - FalseVal->getValue()).isPowerOf2())
|
|
Offset = FalseVal;
|
|
else if ((FalseVal->getValue() - TrueVal->getValue()).isPowerOf2())
|
|
Offset = TrueVal;
|
|
else
|
|
return 0;
|
|
|
|
// Adjust TrueVal and FalseVal to the offset.
|
|
TrueVal = ConstantInt::get(Builder->getContext(),
|
|
TrueVal->getValue() - Offset->getValue());
|
|
FalseVal = ConstantInt::get(Builder->getContext(),
|
|
FalseVal->getValue() - Offset->getValue());
|
|
}
|
|
|
|
// Make sure the mask in the 'and' and one of the select arms is a power of 2.
|
|
if (!AndRHS->getValue().isPowerOf2() ||
|
|
(!TrueVal->getValue().isPowerOf2() &&
|
|
!FalseVal->getValue().isPowerOf2()))
|
|
return 0;
|
|
|
|
// Determine which shift is needed to transform result of the 'and' into the
|
|
// desired result.
|
|
ConstantInt *ValC = !TrueVal->isZero() ? TrueVal : FalseVal;
|
|
unsigned ValZeros = ValC->getValue().logBase2();
|
|
unsigned AndZeros = AndRHS->getValue().logBase2();
|
|
|
|
Value *V = LHS;
|
|
if (ValZeros > AndZeros)
|
|
V = Builder->CreateShl(V, ValZeros - AndZeros);
|
|
else if (ValZeros < AndZeros)
|
|
V = Builder->CreateLShr(V, AndZeros - ValZeros);
|
|
|
|
// Okay, now we know that everything is set up, we just don't know whether we
|
|
// have a icmp_ne or icmp_eq and whether the true or false val is the zero.
|
|
bool ShouldNotVal = !TrueVal->isZero();
|
|
ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
|
|
if (ShouldNotVal)
|
|
V = Builder->CreateXor(V, ValC);
|
|
|
|
// Apply an offset if needed.
|
|
if (Offset)
|
|
V = Builder->CreateAdd(V, Offset);
|
|
return V;
|
|
}
|
|
|
|
Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
|
|
Value *CondVal = SI.getCondition();
|
|
Value *TrueVal = SI.getTrueValue();
|
|
Value *FalseVal = SI.getFalseValue();
|
|
|
|
if (Value *V = SimplifySelectInst(CondVal, TrueVal, FalseVal, TD))
|
|
return ReplaceInstUsesWith(SI, V);
|
|
|
|
if (SI.getType()->isIntegerTy(1)) {
|
|
if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) {
|
|
if (C->getZExtValue()) {
|
|
// Change: A = select B, true, C --> A = or B, C
|
|
return BinaryOperator::CreateOr(CondVal, FalseVal);
|
|
}
|
|
// Change: A = select B, false, C --> A = and !B, C
|
|
Value *NotCond =
|
|
InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
|
|
"not."+CondVal->getName()), SI);
|
|
return BinaryOperator::CreateAnd(NotCond, FalseVal);
|
|
} else if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) {
|
|
if (C->getZExtValue() == false) {
|
|
// Change: A = select B, C, false --> A = and B, C
|
|
return BinaryOperator::CreateAnd(CondVal, TrueVal);
|
|
}
|
|
// Change: A = select B, C, true --> A = or !B, C
|
|
Value *NotCond =
|
|
InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
|
|
"not."+CondVal->getName()), SI);
|
|
return BinaryOperator::CreateOr(NotCond, TrueVal);
|
|
}
|
|
|
|
// select a, b, a -> a&b
|
|
// select a, a, b -> a|b
|
|
if (CondVal == TrueVal)
|
|
return BinaryOperator::CreateOr(CondVal, FalseVal);
|
|
else if (CondVal == FalseVal)
|
|
return BinaryOperator::CreateAnd(CondVal, TrueVal);
|
|
}
|
|
|
|
// Selecting between two integer constants?
|
|
if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
|
|
if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
|
|
// select C, 1, 0 -> zext C to int
|
|
if (FalseValC->isZero() && TrueValC->getValue() == 1)
|
|
return new ZExtInst(CondVal, SI.getType());
|
|
|
|
// select C, -1, 0 -> sext C to int
|
|
if (FalseValC->isZero() && TrueValC->isAllOnesValue())
|
|
return new SExtInst(CondVal, SI.getType());
|
|
|
|
// select C, 0, 1 -> zext !C to int
|
|
if (TrueValC->isZero() && FalseValC->getValue() == 1) {
|
|
Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
|
|
return new ZExtInst(NotCond, SI.getType());
|
|
}
|
|
|
|
// select C, 0, -1 -> sext !C to int
|
|
if (TrueValC->isZero() && FalseValC->isAllOnesValue()) {
|
|
Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
|
|
return new SExtInst(NotCond, SI.getType());
|
|
}
|
|
|
|
if (Value *V = foldSelectICmpAnd(SI, TrueValC, FalseValC, Builder))
|
|
return ReplaceInstUsesWith(SI, V);
|
|
}
|
|
|
|
// See if we are selecting two values based on a comparison of the two values.
|
|
if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
|
|
if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
|
|
// Transform (X == Y) ? X : Y -> Y
|
|
if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
|
|
// This is not safe in general for floating point:
|
|
// consider X== -0, Y== +0.
|
|
// It becomes safe if either operand is a nonzero constant.
|
|
ConstantFP *CFPt, *CFPf;
|
|
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
|
|
!CFPt->getValueAPF().isZero()) ||
|
|
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
|
|
!CFPf->getValueAPF().isZero()))
|
|
return ReplaceInstUsesWith(SI, FalseVal);
|
|
}
|
|
// Transform (X une Y) ? X : Y -> X
|
|
if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
|
|
// This is not safe in general for floating point:
|
|
// consider X== -0, Y== +0.
|
|
// It becomes safe if either operand is a nonzero constant.
|
|
ConstantFP *CFPt, *CFPf;
|
|
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
|
|
!CFPt->getValueAPF().isZero()) ||
|
|
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
|
|
!CFPf->getValueAPF().isZero()))
|
|
return ReplaceInstUsesWith(SI, TrueVal);
|
|
}
|
|
// NOTE: if we wanted to, this is where to detect MIN/MAX
|
|
|
|
} else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
|
|
// Transform (X == Y) ? Y : X -> X
|
|
if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
|
|
// This is not safe in general for floating point:
|
|
// consider X== -0, Y== +0.
|
|
// It becomes safe if either operand is a nonzero constant.
|
|
ConstantFP *CFPt, *CFPf;
|
|
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
|
|
!CFPt->getValueAPF().isZero()) ||
|
|
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
|
|
!CFPf->getValueAPF().isZero()))
|
|
return ReplaceInstUsesWith(SI, FalseVal);
|
|
}
|
|
// Transform (X une Y) ? Y : X -> Y
|
|
if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
|
|
// This is not safe in general for floating point:
|
|
// consider X== -0, Y== +0.
|
|
// It becomes safe if either operand is a nonzero constant.
|
|
ConstantFP *CFPt, *CFPf;
|
|
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
|
|
!CFPt->getValueAPF().isZero()) ||
|
|
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
|
|
!CFPf->getValueAPF().isZero()))
|
|
return ReplaceInstUsesWith(SI, TrueVal);
|
|
}
|
|
// NOTE: if we wanted to, this is where to detect MIN/MAX
|
|
}
|
|
// NOTE: if we wanted to, this is where to detect ABS
|
|
}
|
|
|
|
// See if we are selecting two values based on a comparison of the two values.
|
|
if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal))
|
|
if (Instruction *Result = visitSelectInstWithICmp(SI, ICI))
|
|
return Result;
|
|
|
|
if (Instruction *TI = dyn_cast<Instruction>(TrueVal))
|
|
if (Instruction *FI = dyn_cast<Instruction>(FalseVal))
|
|
if (TI->hasOneUse() && FI->hasOneUse()) {
|
|
Instruction *AddOp = 0, *SubOp = 0;
|
|
|
|
// Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
|
|
if (TI->getOpcode() == FI->getOpcode())
|
|
if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
|
|
return IV;
|
|
|
|
// Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is
|
|
// even legal for FP.
|
|
if ((TI->getOpcode() == Instruction::Sub &&
|
|
FI->getOpcode() == Instruction::Add) ||
|
|
(TI->getOpcode() == Instruction::FSub &&
|
|
FI->getOpcode() == Instruction::FAdd)) {
|
|
AddOp = FI; SubOp = TI;
|
|
} else if ((FI->getOpcode() == Instruction::Sub &&
|
|
TI->getOpcode() == Instruction::Add) ||
|
|
(FI->getOpcode() == Instruction::FSub &&
|
|
TI->getOpcode() == Instruction::FAdd)) {
|
|
AddOp = TI; SubOp = FI;
|
|
}
|
|
|
|
if (AddOp) {
|
|
Value *OtherAddOp = 0;
|
|
if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
|
|
OtherAddOp = AddOp->getOperand(1);
|
|
} else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
|
|
OtherAddOp = AddOp->getOperand(0);
|
|
}
|
|
|
|
if (OtherAddOp) {
|
|
// So at this point we know we have (Y -> OtherAddOp):
|
|
// select C, (add X, Y), (sub X, Z)
|
|
Value *NegVal; // Compute -Z
|
|
if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
|
|
NegVal = ConstantExpr::getNeg(C);
|
|
} else if (SI.getType()->isFloatingPointTy()) {
|
|
NegVal = InsertNewInstBefore(
|
|
BinaryOperator::CreateFNeg(SubOp->getOperand(1),
|
|
"tmp"), SI);
|
|
} else {
|
|
NegVal = InsertNewInstBefore(
|
|
BinaryOperator::CreateNeg(SubOp->getOperand(1),
|
|
"tmp"), SI);
|
|
}
|
|
|
|
Value *NewTrueOp = OtherAddOp;
|
|
Value *NewFalseOp = NegVal;
|
|
if (AddOp != TI)
|
|
std::swap(NewTrueOp, NewFalseOp);
|
|
Instruction *NewSel =
|
|
SelectInst::Create(CondVal, NewTrueOp,
|
|
NewFalseOp, SI.getName() + ".p");
|
|
|
|
NewSel = InsertNewInstBefore(NewSel, SI);
|
|
if (SI.getType()->isFloatingPointTy())
|
|
return BinaryOperator::CreateFAdd(SubOp->getOperand(0), NewSel);
|
|
else
|
|
return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
|
|
}
|
|
}
|
|
}
|
|
|
|
// See if we can fold the select into one of our operands.
|
|
if (SI.getType()->isIntegerTy()) {
|
|
if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
|
|
return FoldI;
|
|
|
|
// MAX(MAX(a, b), a) -> MAX(a, b)
|
|
// MIN(MIN(a, b), a) -> MIN(a, b)
|
|
// MAX(MIN(a, b), a) -> a
|
|
// MIN(MAX(a, b), a) -> a
|
|
Value *LHS, *RHS, *LHS2, *RHS2;
|
|
if (SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS)) {
|
|
if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2))
|
|
if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
|
|
SI, SPF, RHS))
|
|
return R;
|
|
if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2))
|
|
if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2,
|
|
SI, SPF, LHS))
|
|
return R;
|
|
}
|
|
|
|
// TODO.
|
|
// ABS(-X) -> ABS(X)
|
|
// ABS(ABS(X)) -> ABS(X)
|
|
}
|
|
|
|
// See if we can fold the select into a phi node if the condition is a select.
|
|
if (isa<PHINode>(SI.getCondition()))
|
|
// The true/false values have to be live in the PHI predecessor's blocks.
|
|
if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) &&
|
|
CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI))
|
|
if (Instruction *NV = FoldOpIntoPhi(SI))
|
|
return NV;
|
|
|
|
if (SelectInst *TrueSI = dyn_cast<SelectInst>(TrueVal)) {
|
|
if (TrueSI->getCondition() == CondVal) {
|
|
SI.setOperand(1, TrueSI->getTrueValue());
|
|
return &SI;
|
|
}
|
|
}
|
|
if (SelectInst *FalseSI = dyn_cast<SelectInst>(FalseVal)) {
|
|
if (FalseSI->getCondition() == CondVal) {
|
|
SI.setOperand(2, FalseSI->getFalseValue());
|
|
return &SI;
|
|
}
|
|
}
|
|
|
|
if (BinaryOperator::isNot(CondVal)) {
|
|
SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
|
|
SI.setOperand(1, FalseVal);
|
|
SI.setOperand(2, TrueVal);
|
|
return &SI;
|
|
}
|
|
|
|
return 0;
|
|
}
|