[InstCombine] Deal with -(trunc(X >>u 63)) -> trunc(X >>s 63)
Identical to it's trunc-less variant, just pretent-to hoist
trunc, and everything else still holds:
https://rise4fun.com/Alive/JRU
llvm-svn: 373364
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 7e3d405..40cc188 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1666,29 +1666,42 @@
const APInt *Op0C;
if (match(Op0, m_APInt(Op0C))) {
- unsigned BitWidth = I.getType()->getScalarSizeInBits();
- // -(X >>u 31) -> (X >>s 31)
- // -(X >>s 31) -> (X >>u 31)
if (Op0C->isNullValue()) {
+ Value *Op1Wide;
+ match(Op1, m_TruncOrSelf(m_Value(Op1Wide)));
+ bool HadTrunc = Op1Wide != Op1;
+ bool NoTruncOrTruncIsOneUse = !HadTrunc || Op1->hasOneUse();
+ unsigned BitWidth = Op1Wide->getType()->getScalarSizeInBits();
+
Value *X;
const APInt *ShAmt;
- if (match(Op1, m_LShr(m_Value(X), m_APInt(ShAmt))) &&
+ // -(X >>u 31) -> (X >>s 31)
+ if (NoTruncOrTruncIsOneUse &&
+ match(Op1Wide, m_LShr(m_Value(X), m_APInt(ShAmt))) &&
*ShAmt == BitWidth - 1) {
- Value *ShAmtOp = cast<Instruction>(Op1)->getOperand(1);
+ Value *ShAmtOp = cast<Instruction>(Op1Wide)->getOperand(1);
Instruction *NewShift = BinaryOperator::CreateAShr(X, ShAmtOp);
- NewShift->copyIRFlags(Op1);
- return NewShift;
+ NewShift->copyIRFlags(Op1Wide);
+ if (!HadTrunc)
+ return NewShift;
+ Builder.Insert(NewShift);
+ return TruncInst::CreateTruncOrBitCast(NewShift, Op1->getType());
}
- if (match(Op1, m_AShr(m_Value(X), m_APInt(ShAmt))) &&
+ // -(X >>s 31) -> (X >>u 31)
+ if (NoTruncOrTruncIsOneUse &&
+ match(Op1Wide, m_AShr(m_Value(X), m_APInt(ShAmt))) &&
*ShAmt == BitWidth - 1) {
- Value *ShAmtOp = cast<Instruction>(Op1)->getOperand(1);
+ Value *ShAmtOp = cast<Instruction>(Op1Wide)->getOperand(1);
Instruction *NewShift = BinaryOperator::CreateLShr(X, ShAmtOp);
- NewShift->copyIRFlags(Op1);
- return NewShift;
+ NewShift->copyIRFlags(Op1Wide);
+ if (!HadTrunc)
+ return NewShift;
+ Builder.Insert(NewShift);
+ return TruncInst::CreateTruncOrBitCast(NewShift, Op1->getType());
}
- if (Op1->hasOneUse()) {
+ if (!HadTrunc && Op1->hasOneUse()) {
Value *LHS, *RHS;
SelectPatternFlavor SPF = matchSelectPattern(Op1, LHS, RHS).Flavor;
if (SPF == SPF_ABS || SPF == SPF_NABS) {