Multiply can be evaluated in a different type, so long as the target type has
a smaller bitwidth.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46244 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 2ad592a..3e009eb 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -6512,6 +6512,15 @@
CanEvaluateInDifferentType(I->getOperand(1), Ty, CastOpc,
NumCastsRemoved);
+ case Instruction::Mul:
+ break;
+ // A multiply can be truncated by truncating its operands.
+ return Ty->getBitWidth() < OrigTy->getBitWidth() &&
+ CanEvaluateInDifferentType(I->getOperand(0), Ty, CastOpc,
+ NumCastsRemoved) &&
+ CanEvaluateInDifferentType(I->getOperand(1), Ty, CastOpc,
+ NumCastsRemoved);
+
case Instruction::Shl:
// If we are truncating the result of this SHL, and if it's a shift of a
// constant amount, we can always perform a SHL in a smaller type.
@@ -6571,6 +6580,7 @@
switch (I->getOpcode()) {
case Instruction::Add:
case Instruction::Sub:
+ case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor: