forked from OSchip/llvm-project
[InstCombine] clean up adjustMinMax(); NFCI
1. Change param names for readability 2. Change pointer param to ref 3. Early exit to reduce indent 4. Change switch to if/else llvm-svn: 285718
This commit is contained in:
Sanjay Patel
parent
cf8a59e449
commit
644d7c3b8a
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@ -416,107 +416,102 @@ static Value *foldSelectCttzCtlz(ICmpInst *ICI, Value *TrueVal, Value *FalseVal,
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/// Return true if we find and adjust an icmp+select pattern where the compare
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/// is with a constant that can be incremented or decremented to match the
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/// minimum or maximum idiom.
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static bool adjustMinMax(SelectInst &SI, 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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static bool adjustMinMax(SelectInst &Sel, ICmpInst &Cmp) {
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ICmpInst::Predicate Pred = Cmp.getPredicate();
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Value *CmpLHS = Cmp.getOperand(0);
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Value *CmpRHS = Cmp.getOperand(1);
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Value *TrueVal = Sel.getTrueValue();
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Value *FalseVal = Sel.getFalseValue();
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// We may move or edit ICI 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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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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IntegerType *SelectTy = dyn_cast<IntegerType>(SI.getType());
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if (!SelectTy)
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break;
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// We may move or edit the compare, so make sure the select is the only user.
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if (!Cmp.hasOneUse())
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return false;
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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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// FIXME: Use m_APInt to allow vector folds.
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auto *CI = dyn_cast<ConstantInt>(CmpRHS);
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if (!CI)
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return false;
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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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// These transformations only work for selects over integers.
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IntegerType *SelectTy = dyn_cast<IntegerType>(Sel.getType());
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if (!SelectTy)
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return false;
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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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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 if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_SLT)
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AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() - 1);
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else
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return false;
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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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// 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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}
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// Types do not match. Instead of calculating this with mixed types, promote
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// all to the larger type. This enables scalar evolution to analyze this
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// expression.
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else if (CmpRHS->getType()->getScalarSizeInBits() < SelectTy->getBitWidth()) {
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Constant *SextRHS = ConstantExpr::getSExt(AdjustedRHS, SelectTy);
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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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SI.swapProfMetadata();
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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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// 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))) && 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 (Cmp.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))) && 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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return false;
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}
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} else {
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return false;
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}
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} else {
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return false;
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}
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return Changed;
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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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Cmp.setPredicate(Pred);
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Cmp.setOperand(0, CmpLHS);
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Cmp.setOperand(1, CmpRHS);
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Sel.setOperand(1, TrueVal);
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Sel.setOperand(2, FalseVal);
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Sel.swapProfMetadata();
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// Move the compare instruction right before the select instruction. Otherwise
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// the sext/zext value may be defined after the compare instruction uses it.
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Cmp.moveBefore(&Sel);
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return true;
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}
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/// Visit a SelectInst that has an ICmpInst as its first operand.
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Instruction *InstCombiner::foldSelectInstWithICmp(SelectInst &SI,
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ICmpInst *ICI) {
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bool Changed = adjustMinMax(SI, ICI);
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bool Changed = adjustMinMax(SI, *ICI);
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ICmpInst::Predicate Pred = ICI->getPredicate();
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Value *CmpLHS = ICI->getOperand(0);
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