[llvm] r228969 - [SDAG] Don't try to use FP_EXTEND/FP_ROUND for int<->fp promotions

[Hal Finkel]

Owen, Hans,

This fixes a regression from 3.5, affecting PowerPC (and perhaps also other out-of-tree targets). Could we bring it into the 3.6 release branch?

Unfortunately, I missed this for a long time because of an oversight on my part in how I was running the test suite. :(

Thanks again,
Hal

----- Original Message -----
> From: "Hal Finkel" <hfinkel at anl.gov>
> To: llvm-commits at cs.uiuc.edu
> Sent: Thursday, February 12, 2015 4:43:52 PM
> Subject: [llvm] r228969 - [SDAG] Don't try to use FP_EXTEND/FP_ROUND for	int<->fp promotions
> 
> Author: hfinkel
> Date: Thu Feb 12 16:43:52 2015
> New Revision: 228969
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=228969&view=rev
> Log:
> [SDAG] Don't try to use FP_EXTEND/FP_ROUND for int<->fp promotions
> 
> The PowerPC backend has long promoted some floating-point vector
> operations
> (such as select) to integer vector operations. Unfortunately, this
> behavior was
> broken by r216555. When using FP_EXTEND/FP_ROUND for promotions, we
> must check
> that both the old and new types are floating-point types. Otherwise,
> we must
> use BITCAST as we did prior to r216555 for everything.
> 
> Added:
>     llvm/trunk/test/CodeGen/PowerPC/vsel-prom.ll
> Modified:
>     llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
> 
> Modified: llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp?rev=228969&r1=228968&r2=228969&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
> (original)
> +++ llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp Thu Feb
> 12 16:43:52 2015
> @@ -390,7 +390,8 @@ SDValue VectorLegalizer::Promote(SDValue
>        if (Op.getOperand(j)
>                .getValueType()
>                .getVectorElementType()
> -              .isFloatingPoint())
> +              .isFloatingPoint() &&
> +          NVT.isVector() &&
> NVT.getVectorElementType().isFloatingPoint())
>          Operands[j] = DAG.getNode(ISD::FP_EXTEND, dl, NVT,
>          Op.getOperand(j));
>        else
>          Operands[j] = DAG.getNode(ISD::BITCAST, dl, NVT,
>          Op.getOperand(j));
> @@ -399,8 +400,9 @@ SDValue VectorLegalizer::Promote(SDValue
>    }
>  
>    Op = DAG.getNode(Op.getOpcode(), dl, NVT, Operands);
> -  if (VT.isFloatingPoint() ||
> -      (VT.isVector() &&
> VT.getVectorElementType().isFloatingPoint()))
> +  if ((VT.isFloatingPoint() && NVT.isFloatingPoint()) ||
> +      (VT.isVector() && VT.getVectorElementType().isFloatingPoint()
> &&
> +       NVT.isVector() &&
> NVT.getVectorElementType().isFloatingPoint()))
>      return DAG.getNode(ISD::FP_ROUND, dl, VT, Op,
>      DAG.getIntPtrConstant(0));
>    else
>      return DAG.getNode(ISD::BITCAST, dl, VT, Op);
> 
> Added: llvm/trunk/test/CodeGen/PowerPC/vsel-prom.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/vsel-prom.ll?rev=228969&view=auto
> ==============================================================================
> --- llvm/trunk/test/CodeGen/PowerPC/vsel-prom.ll (added)
> +++ llvm/trunk/test/CodeGen/PowerPC/vsel-prom.ll Thu Feb 12 16:43:52
> 2015
> @@ -0,0 +1,23 @@
> +; RUN: llc -mcpu=pwr7 < %s | FileCheck %s
> +target datalayout = "E-m:e-i64:64-n32:64"
> +target triple = "powerpc64-unknown-linux-gnu"
> +
> +; Function Attrs: nounwind
> +define void @Compute_Lateral() #0 {
> +entry:
> +  br i1 undef, label %if.then, label %if.end
> +
> +if.then:                                          ; preds = %entry
> +  unreachable
> +
> +if.end:                                           ; preds = %entry
> +  %0 = select i1 undef, <2 x double> undef, <2 x double>
> zeroinitializer
> +  %1 = extractelement <2 x double> %0, i32 1
> +  store double %1, double* undef, align 8
> +  ret void
> +
> +; CHECK-LABEL: @Compute_Lateral
> +}
> +
> +attributes #0 = { nounwind }
> +
> 
> 
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> 

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory