[llvm-commits] [llvm] r156023 - in /llvm/trunk: lib/CodeGen/SelectionDAG/DAGCombiner.cpp test/CodeGen/ARM/fmuls.ll

[Jim Grosbach]

Apologies for the possibly naive question, but is this transformation valid if the input is a NaN or denormal? I suspect so for the latter, but am more unsure about the former.

-Jim

On May 2, 2012, at 2:32 PM, Owen Anderson <resistor at mac.com> wrote:

> Author: resistor
> Date: Wed May  2 16:32:35 2012
> New Revision: 156023
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=156023&view=rev
> Log:
> Teach DAG combine that multiplication by 1.0 can always be constant folded.
> 
> Modified:
>    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>    llvm/trunk/test/CodeGen/ARM/fmuls.ll
> 
> Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=156023&r1=156022&r2=156023&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
> +++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Wed May  2 16:32:35 2012
> @@ -5715,6 +5715,9 @@
>   if (DAG.getTarget().Options.UnsafeFPMath &&
>       ISD::isBuildVectorAllZeros(N1.getNode()))
>     return N1;
> +  // fold (fmul A, 1.0) -> A
> +  if (N1CFP && N1CFP->isExactlyValue(1.0))
> +    return N0;
>   // fold (fmul X, 2.0) -> (fadd X, X)
>   if (N1CFP && N1CFP->isExactlyValue(+2.0))
>     return DAG.getNode(ISD::FADD, N->getDebugLoc(), VT, N0, N0);
> 
> Modified: llvm/trunk/test/CodeGen/ARM/fmuls.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/fmuls.ll?rev=156023&r1=156022&r2=156023&view=diff
> ==============================================================================
> --- llvm/trunk/test/CodeGen/ARM/fmuls.ll (original)
> +++ llvm/trunk/test/CodeGen/ARM/fmuls.ll Wed May  2 16:32:35 2012
> @@ -21,3 +21,12 @@
> ; CORTEXA8: 	vmul.f32	d0, d1, d0
> ; CORTEXA9: test:
> ; CORTEXA9: 	vmul.f32	s{{.}}, s{{.}}, s{{.}}
> +
> +; VFP2: test2
> +define float @test2(float %a) nounwind {
> +; CHECK-NOT: mul
> +; CHECK: mov pc, lr
> +  %ret = fmul float %a, 1.0
> +  ret float %ret
> +}
> +
> 
> 
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