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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
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@ -6512,6 +6512,15 @@ static bool CanEvaluateInDifferentType(Value *V, const IntegerType *Ty,
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CanEvaluateInDifferentType(I->getOperand(1), Ty, CastOpc,
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NumCastsRemoved);
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case Instruction::Mul:
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break;
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// A multiply can be truncated by truncating its operands.
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return Ty->getBitWidth() < OrigTy->getBitWidth() &&
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CanEvaluateInDifferentType(I->getOperand(0), Ty, CastOpc,
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NumCastsRemoved) &&
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CanEvaluateInDifferentType(I->getOperand(1), Ty, CastOpc,
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NumCastsRemoved);
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case Instruction::Shl:
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// If we are truncating the result of this SHL, and if it's a shift of a
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// constant amount, we can always perform a SHL in a smaller type.
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@ -6571,6 +6580,7 @@ Value *InstCombiner::EvaluateInDifferentType(Value *V, const Type *Ty,
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switch (I->getOpcode()) {
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case Instruction::Add:
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case Instruction::Sub:
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case Instruction::Mul:
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case Instruction::And:
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case Instruction::Or:
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case Instruction::Xor:
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11
test/Transforms/InstCombine/2008-01-21-MulTrunc.ll
Normal file
11
test/Transforms/InstCombine/2008-01-21-MulTrunc.ll
Normal file
@ -0,0 +1,11 @@
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; RUN: llvm-as < %s | opt -instcombine | llvm-dis | notcast
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define i16 @test1(i16 %a) {
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%tmp = zext i16 %a to i32 ; <i32> [#uses=2]
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%tmp21 = lshr i32 %tmp, 8 ; <i32> [#uses=1]
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%tmp5 = mul i32 %tmp, 5 ; <i32> [#uses=1]
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%tmp.upgrd.32 = or i32 %tmp21, %tmp5 ; <i32> [#uses=1]
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%tmp.upgrd.3 = trunc i32 %tmp.upgrd.32 to i16 ; <i16> [#uses=1]
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ret i16 %tmp.upgrd.3
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}
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