[InstCombine] More thoroughly canonicalize the position of zexts
We correctly canonicalized (add (sext x), (sext y)) to (sext (add x, y))
where possible. However, we didn't perform the same canonicalization
for zexts or for muls.
llvm-svn: 290733
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index c70d758..2f72e0a 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -389,6 +389,79 @@
}
}
+ // Check for (mul (sext x), y), see if we can merge this into an
+ // integer mul followed by a sext.
+ if (SExtInst *Op0Conv = dyn_cast<SExtInst>(Op0)) {
+ // (mul (sext x), cst) --> (sext (mul x, cst'))
+ if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
+ if (Op0Conv->hasOneUse()) {
+ Constant *CI =
+ ConstantExpr::getTrunc(Op1C, Op0Conv->getOperand(0)->getType());
+ if (ConstantExpr::getSExt(CI, I.getType()) == Op1C &&
+ WillNotOverflowSignedMul(Op0Conv->getOperand(0), CI, I)) {
+ // Insert the new, smaller mul.
+ Value *NewMul =
+ Builder->CreateNSWMul(Op0Conv->getOperand(0), CI, "mulconv");
+ return new SExtInst(NewMul, I.getType());
+ }
+ }
+ }
+
+ // (mul (sext x), (sext y)) --> (sext (mul int x, y))
+ if (SExtInst *Op1Conv = dyn_cast<SExtInst>(Op1)) {
+ // Only do this if x/y have the same type, if at last one of them has a
+ // single use (so we don't increase the number of sexts), and if the
+ // integer mul will not overflow.
+ if (Op0Conv->getOperand(0)->getType() ==
+ Op1Conv->getOperand(0)->getType() &&
+ (Op0Conv->hasOneUse() || Op1Conv->hasOneUse()) &&
+ WillNotOverflowSignedMul(Op0Conv->getOperand(0),
+ Op1Conv->getOperand(0), I)) {
+ // Insert the new integer mul.
+ Value *NewMul = Builder->CreateNSWMul(
+ Op0Conv->getOperand(0), Op1Conv->getOperand(0), "mulconv");
+ return new SExtInst(NewMul, I.getType());
+ }
+ }
+ }
+
+ // Check for (mul (zext x), y), see if we can merge this into an
+ // integer mul followed by a zext.
+ if (auto *Op0Conv = dyn_cast<ZExtInst>(Op0)) {
+ // (mul (zext x), cst) --> (zext (mul x, cst'))
+ if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
+ if (Op0Conv->hasOneUse()) {
+ Constant *CI =
+ ConstantExpr::getTrunc(Op1C, Op0Conv->getOperand(0)->getType());
+ if (ConstantExpr::getZExt(CI, I.getType()) == Op1C &&
+ WillNotOverflowSignedMul(Op0Conv->getOperand(0), CI, I)) {
+ // Insert the new, smaller mul.
+ Value *NewMul =
+ Builder->CreateNUWMul(Op0Conv->getOperand(0), CI, "mulconv");
+ return new ZExtInst(NewMul, I.getType());
+ }
+ }
+ }
+
+ // (mul (zext x), (zext y)) --> (zext (mul int x, y))
+ if (auto *Op1Conv = dyn_cast<ZExtInst>(Op1)) {
+ // Only do this if x/y have the same type, if at last one of them has a
+ // single use (so we don't increase the number of zexts), and if the
+ // integer mul will not overflow.
+ if (Op0Conv->getOperand(0)->getType() ==
+ Op1Conv->getOperand(0)->getType() &&
+ (Op0Conv->hasOneUse() || Op1Conv->hasOneUse()) &&
+ computeOverflowForUnsignedMul(Op0Conv->getOperand(0),
+ Op1Conv->getOperand(0),
+ &I) == OverflowResult::NeverOverflows) {
+ // Insert the new integer mul.
+ Value *NewMul = Builder->CreateNUWMul(
+ Op0Conv->getOperand(0), Op1Conv->getOperand(0), "mulconv");
+ return new ZExtInst(NewMul, I.getType());
+ }
+ }
+ }
+
if (!I.hasNoSignedWrap() && WillNotOverflowSignedMul(Op0, Op1, I)) {
Changed = true;
I.setHasNoSignedWrap(true);