[llvm-commits] [llvm] r46244 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/2008-01-21-MulTrunc.ll

[Nate Begeman]

I don't get different output for the attached patch before and after  
the patch, and the test fails.

On Jan 21, 2008, at 9:08 PM, Nick Lewycky wrote:

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> ======================================================================
> --- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp  
> (original)
> +++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Mon  
> Jan 21 23:08:48 2008
> @@ -6512,6 +6512,15 @@
>            CanEvaluateInDifferentType(I->getOperand(1), Ty, CastOpc,
>                                       NumCastsRemoved);
>
> +  case Instruction::Mul:
> +    break;

Probably due to this 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:
>
> Added: llvm/trunk/test/Transforms/InstCombine/2008-01-21-MulTrunc.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/2008-01-21-MulTrunc.ll?rev=46244&view=auto
>
> = 
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> ======================================================================
> --- llvm/trunk/test/Transforms/InstCombine/2008-01-21-MulTrunc.ll  
> (added)
> +++ llvm/trunk/test/Transforms/InstCombine/2008-01-21-MulTrunc.ll  
> Mon Jan 21 23:08:48 2008
> @@ -0,0 +1,11 @@
> +; RUN: llvm-as < %s | opt -instcombine | llvm-dis | notcast
> +
> +define i16 @test1(i16 %a) {
> +        %tmp = zext i16 %a to i32               ; <i32> [#uses=2]
> +        %tmp21 = lshr i32 %tmp, 8               ; <i32> [#uses=1]
> +        %tmp5 = mul i32 %tmp, 5         ; <i32> [#uses=1]
> +        %tmp.upgrd.32 = or i32 %tmp21, %tmp5            ; <i32>  
> [#uses=1]
> +        %tmp.upgrd.3 = trunc i32 %tmp.upgrd.32 to i16           ;  
> <i16> [#uses=1]
> +        ret i16 %tmp.upgrd.3
> +}
> +
>
>
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