[InstCombine] enable (X >>?exact C1) << C2 --> X >>?exact (C1-C2) for vectors with splat constants
llvm-svn: 293524
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
index fb90814..edd51ba 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
@@ -373,18 +373,6 @@
if (ShiftAmt2 < ShiftAmt1) {
uint32_t ShiftDiff = ShiftAmt1 - ShiftAmt2;
- // (X >>?exact C1) << C2 --> X >>?exact (C1-C2)
- // The inexact version is deferred to DAGCombine so we don't hide shl
- // behind a bit mask.
- if (I.getOpcode() == Instruction::Shl &&
- ShiftOp->getOpcode() != Instruction::Shl && ShiftOp->isExact()) {
- ConstantInt *ShiftDiffCst = ConstantInt::get(Ty, ShiftDiff);
- BinaryOperator *NewShr =
- BinaryOperator::Create(ShiftOp->getOpcode(), X, ShiftDiffCst);
- NewShr->setIsExact(true);
- return NewShr;
- }
-
// (X << C1) >>u C2 --> X << (C1-C2) & (-1 >> C2)
if (I.getOpcode() == Instruction::LShr &&
ShiftOp->getOpcode() == Instruction::Shl) {
@@ -670,18 +658,28 @@
return BinaryOperator::CreateAnd(X, ConstantInt::get(Ty, Mask));
}
- const APInt *ShrAmt;
- if (match(Op0, m_CombineOr(m_Exact(m_LShr(m_Value(X), m_APInt(ShrAmt))),
- m_Exact(m_AShr(m_Value(X), m_APInt(ShrAmt))))) &&
- ShrAmt->ult(*ShAmtAPInt)) {
- // If C1 < C2: (X >>?,exact C1) << C2 --> X << (C2 - C1)
- // The inexact version is deferred to DAGCombine, so we don't hide shl
- // behind a bit mask.
- Constant *ShiftDiffCst = ConstantInt::get(Ty, *ShAmtAPInt - *ShrAmt);
- auto *NewShl = BinaryOperator::CreateShl(X, ShiftDiffCst);
- NewShl->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
- NewShl->setHasNoSignedWrap(I.hasNoSignedWrap());
- return NewShl;
+ // The inexact versions are deferred to DAGCombine, so we don't hide shl
+ // behind a bit mask.
+ const APInt *ShrOp1;
+ if (match(Op0, m_CombineOr(m_Exact(m_LShr(m_Value(X), m_APInt(ShrOp1))),
+ m_Exact(m_AShr(m_Value(X), m_APInt(ShrOp1)))))) {
+ unsigned ShrAmt = ShrOp1->getZExtValue();
+ if (ShrAmt < ShAmt) {
+ // If C1 < C2: (X >>?,exact C1) << C2 --> X << (C2 - C1)
+ Constant *ShiftDiff = ConstantInt::get(Ty, ShAmt - ShrAmt);
+ auto *NewShl = BinaryOperator::CreateShl(X, ShiftDiff);
+ NewShl->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
+ NewShl->setHasNoSignedWrap(I.hasNoSignedWrap());
+ return NewShl;
+ }
+ if (ShrAmt > ShAmt) {
+ // If C1 > C2: (X >>?exact C1) << C2 --> X >>?exact (C1 - C2)
+ Constant *ShiftDiff = ConstantInt::get(Ty, ShrAmt - ShAmt);
+ auto *NewShr = BinaryOperator::Create(
+ cast<BinaryOperator>(Op0)->getOpcode(), X, ShiftDiff);
+ NewShr->setIsExact(true);
+ return NewShr;
+ }
}
// If the shifted-out value is known-zero, then this is a NUW shift.