[llvm-commits] [llvm] r171467 - in /llvm/trunk: lib/Target/X86/X86ISelLowering.cpp test/CodeGen/X86/avx-trunc.ll

[Demikhovsky, Elena]

Oh, you are right..

- Elena

-----Original Message-----
From: Nadav Rotem [mailto:nrotem at apple.com] 
Sent: Thursday, January 03, 2013 19:21
To: Demikhovsky, Elena
Cc: llvm-commits at cs.uiuc.edu
Subject: Re: [llvm-commits] [llvm] r171467 - in /llvm/trunk: lib/Target/X86/X86ISelLowering.cpp test/CodeGen/X86/avx-trunc.ll

Elena, 

How is this correct ?    You are taking the result of SETCC which is a vector or v8i32, and you only take the lower 4 elements (v4i32).  The SETCC is not all-one or all zero. Only *elements* within the vector are all-one or all zero. Did you test this patch somehow ? 

Nadav


On Jan 3, 2013, at 12:49 AM, Elena Demikhovsky <elena.demikhovsky at intel.com> wrote:

> Author: delena
> Date: Thu Jan  3 02:48:33 2013
> New Revision: 171467
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=171467&view=rev
> Log:
> Simplified TRUNCATE operation that comes after SETCC. It is possible since SETCC result is 0 or -1.
> Added a test.
> 
> Modified:
>    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
>    llvm/trunk/test/CodeGen/X86/avx-trunc.ll
> 
> Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
> URL: 
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelL
> owering.cpp?rev=171467&r1=171466&r2=171467&view=diff
> ======================================================================
> ========
> --- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
> +++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Thu Jan  3 02:48:33 
> +++ 2013
> @@ -14661,12 +14661,29 @@
>   return EltsFromConsecutiveLoads(VT, Elts, dl, DAG); }
> 
> -/// PerformTruncateCombine - Converts truncate operation to -/// a 
> sequence of vector shuffle operations.
> -/// It is possible when we truncate 256-bit vector to 128-bit vector
> +/// PerformTruncateCombine - In some cases a sequence with "truncate"
> +/// operation may be simplified.
> static SDValue PerformTruncateCombine(SDNode *N, SelectionDAG &DAG,
>                                       TargetLowering::DAGCombinerInfo &DCI,
>                                       const X86Subtarget *Subtarget)  
> {
> +  EVT VT = N->getValueType(0);
> +  if (DCI.isBeforeLegalize() || !VT.isVector())
> +    return SDValue();
> +
> +  SDValue In = N->getOperand(0);
> +  // Optimize the sequence setcc -> truncate  if (In.getOpcode() == 
> + ISD::SETCC) {
> +    DebugLoc DL = N->getDebugLoc();
> +    EVT InVT = In.getValueType();
> +
> +    // The vector element is all ones or all zero. Just take a half of it.
> +    EVT HalfVT = EVT::getVectorVT(*DAG.getContext(), InVT.getScalarType(),
> +                                  InVT.getVectorNumElements()/2);
> +    SDValue HalfVec = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, HalfVT, In,
> +                                  DAG.getIntPtrConstant(0));
> +    assert(HalfVT.getSizeInBits() == VT.getSizeInBits());
> +    return DAG.getNode(ISD::BITCAST, DL, VT, HalfVec);  }
>   return SDValue();
> }
> 
> 
> Modified: llvm/trunk/test/CodeGen/X86/avx-trunc.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/avx-trunc.ll?rev=171467&r1=171466&r2=171467&view=diff
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/avx-trunc.ll (original)
> +++ llvm/trunk/test/CodeGen/X86/avx-trunc.ll Thu Jan  3 02:48:33 2013
> @@ -13,3 +13,18 @@
>   ret <8 x i16>%B
> }
> 
> +define <8 x i16> @trunc_after_setcc(<8 x float> %a, <8 x float> %b, <8 x float> %c, <8 x float> %d) {
> +; CHECK: trunc_after_setcc
> +; CHECK: vcmpltps
> +; CHECK-NOT: vextract
> +; CHECK: vcmpltps
> +; CHECK-NEXT: vandps
> +; CHECK-NEXT: vandps
> +; CHECK: ret
> +  %res1 = fcmp olt <8 x float> %a, %b
> +  %res2 = fcmp olt <8 x float> %c, %d
> +  %andr = and <8 x i1>%res1, %res2
> +  %ex = zext <8 x i1> %andr to <8 x i16>
> +  ret <8 x i16>%ex
> +}
> +
> 
> 
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