InstCombine: Match min/max hidden by sext/zext
X = sext x; x >s c ? X : C+1 --> X = sext x; X <s C+1 ? C+1 : X
X = sext x; x <s c ? X : C-1 --> X = sext x; X >s C-1 ? C-1 : X
X = zext x; x >u c ? X : C+1 --> X = zext x; X <u C+1 ? C+1 : X
X = zext x; x <u c ? X : C-1 --> X = zext x; X >u C-1 ? C-1 : X
X = sext x; x >u c ? X : C+1 --> X = sext x; X <u C+1 ? C+1 : X
X = sext x; x <u c ? X : C-1 --> X = sext x; X >u C-1 ? C-1 : X
Instead of calculating this with mixed types promote all to the
larger type. This enables scalar evolution to analyze this
expression. PR8866
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123034 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineSelect.cpp b/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 03a030d..c2caedf 100644
--- a/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -285,48 +285,83 @@
// place here, so make sure the select is the only user.
if (ICI->hasOneUse())
if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) {
+ // X < MIN ? T : F --> F
+ if ((Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_ULT)
+ && CI->isMinValue(Pred == ICmpInst::ICMP_SLT))
+ return ReplaceInstUsesWith(SI, FalseVal);
+ // X > MAX ? T : F --> F
+ else if ((Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_UGT)
+ && CI->isMaxValue(Pred == ICmpInst::ICMP_SGT))
+ return ReplaceInstUsesWith(SI, FalseVal);
switch (Pred) {
default: break;
case ICmpInst::ICMP_ULT:
- case ICmpInst::ICMP_SLT: {
- // X < MIN ? T : F --> F
- if (CI->isMinValue(Pred == ICmpInst::ICMP_SLT))
- return ReplaceInstUsesWith(SI, FalseVal);
- // X < C ? X : C-1 --> X > C-1 ? C-1 : X
- Constant *AdjustedRHS =
- ConstantInt::get(CI->getContext(), CI->getValue()-1);
- if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
- (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) {
- Pred = ICmpInst::getSwappedPredicate(Pred);
- CmpRHS = AdjustedRHS;
- std::swap(FalseVal, TrueVal);
- ICI->setPredicate(Pred);
- ICI->setOperand(1, CmpRHS);
- SI.setOperand(1, TrueVal);
- SI.setOperand(2, FalseVal);
- Changed = true;
- }
- break;
- }
+ case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_SGT: {
- // X > MAX ? T : F --> F
- if (CI->isMaxValue(Pred == ICmpInst::ICMP_SGT))
- return ReplaceInstUsesWith(SI, FalseVal);
+ Constant *AdjustedRHS;
+ if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_SGT)
+ AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() + 1);
+ else // (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_SLT)
+ AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() - 1);
+
// X > C ? X : C+1 --> X < C+1 ? C+1 : X
- Constant *AdjustedRHS =
- ConstantInt::get(CI->getContext(), CI->getValue()+1);
+ // X < C ? X : C-1 --> X > C-1 ? C-1 : X
if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
- (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) {
- Pred = ICmpInst::getSwappedPredicate(Pred);
- CmpRHS = AdjustedRHS;
- std::swap(FalseVal, TrueVal);
- ICI->setPredicate(Pred);
- ICI->setOperand(1, CmpRHS);
- SI.setOperand(1, TrueVal);
- SI.setOperand(2, FalseVal);
- Changed = true;
- }
+ (CmpLHS == FalseVal && AdjustedRHS == TrueVal))
+ ; // Nothing to do here. Values match without any sign/zero extension.
+
+ // Types do not match. Instead of calculating this with mixed types
+ // promote all to the larger type. This enables scalar evolution to
+ // analyze this expression.
+ else if (CmpRHS->getType()->getScalarSizeInBits()
+ < SI.getType()->getScalarSizeInBits()) {
+ Constant *sextRHS = ConstantExpr::getSExt(AdjustedRHS,
+ SI.getType());
+
+ // X = sext x; x >s c ? X : C+1 --> X = sext x; X <s C+1 ? C+1 : X
+ // X = sext x; x <s c ? X : C-1 --> X = sext x; X >s C-1 ? C-1 : X
+ // X = sext x; x >u c ? X : C+1 --> X = sext x; X <u C+1 ? C+1 : X
+ // X = sext x; x <u c ? X : C-1 --> X = sext x; X >u C-1 ? C-1 : X
+ if (match(TrueVal, m_SExt(m_Specific(CmpLHS))) &&
+ sextRHS == FalseVal) {
+ CmpLHS = TrueVal;
+ AdjustedRHS = sextRHS;
+ } else if (match(FalseVal, m_SExt(m_Specific(CmpLHS))) &&
+ sextRHS == TrueVal) {
+ CmpLHS = FalseVal;
+ AdjustedRHS = sextRHS;
+ } else if (ICI->isUnsigned()) {
+ Constant *zextRHS = ConstantExpr::getZExt(AdjustedRHS,
+ SI.getType());
+ // X = zext x; x >u c ? X : C+1 --> X = zext x; X <u C+1 ? C+1 : X
+ // X = zext x; x <u c ? X : C-1 --> X = zext x; X >u C-1 ? C-1 : X
+ // zext + signed compare cannot be changed:
+ // 0xff <s 0x00, but 0x00ff >s 0x0000
+ if (match(TrueVal, m_ZExt(m_Specific(CmpLHS))) &&
+ zextRHS == FalseVal) {
+ CmpLHS = TrueVal;
+ AdjustedRHS = zextRHS;
+ } else if (match(FalseVal, m_ZExt(m_Specific(CmpLHS))) &&
+ zextRHS == TrueVal) {
+ CmpLHS = FalseVal;
+ AdjustedRHS = zextRHS;
+ } else
+ break;
+ } else
+ break;
+ } else
+ break;
+
+ Pred = ICmpInst::getSwappedPredicate(Pred);
+ CmpRHS = AdjustedRHS;
+ std::swap(FalseVal, TrueVal);
+ ICI->setPredicate(Pred);
+ ICI->setOperand(0, CmpLHS);
+ ICI->setOperand(1, CmpRHS);
+ SI.setOperand(1, TrueVal);
+ SI.setOperand(2, FalseVal);
+ Changed = true;
break;
}
}