[llvm] r339533 - [SelectionDAG] In PromoteFloatRes_BITCAST, insert a bitcast before the fp16_to_fp in case the input type isn't an i16.

[Hans Wennborg via llvm-commits]

Merged to 7.0 in r339855.

On Mon, Aug 13, 2018 at 7:26 AM, Craig Topper via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: ctopper
> Date: Sun Aug 12 22:26:49 2018
> New Revision: 339533
>
> URL: http://llvm.org/viewvc/llvm-project?rev=339533&view=rev
> Log:
> [SelectionDAG] In PromoteFloatRes_BITCAST, insert a bitcast before the fp16_to_fp in case the input type isn't an i16.
>
> The bitcast can be further legalized as needed.
>
> Fixes PR38533.
>
> Added:
>     llvm/trunk/test/CodeGen/X86/pr38533.ll
> Modified:
>     llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
>
> Modified: llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp?rev=339533&r1=339532&r2=339533&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp (original)
> +++ llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp Sun Aug 12 22:26:49 2018
> @@ -1941,8 +1941,10 @@ void DAGTypeLegalizer::PromoteFloatResul
>  SDValue DAGTypeLegalizer::PromoteFloatRes_BITCAST(SDNode *N) {
>    EVT VT = N->getValueType(0);
>    EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), VT);
> -  return DAG.getNode(GetPromotionOpcode(VT, NVT), SDLoc(N), NVT,
> -                     N->getOperand(0));
> +  // Input type isn't guaranteed to be i16 so bitcast if not. The bitcast
> +  // will be legalized further if necessary.
> +  SDValue Cast = DAG.getBitcast(MVT::i16, N->getOperand(0));
> +  return DAG.getNode(GetPromotionOpcode(VT, NVT), SDLoc(N), NVT, Cast);
>  }
>
>  SDValue DAGTypeLegalizer::PromoteFloatRes_ConstantFP(SDNode *N) {
>
> Added: llvm/trunk/test/CodeGen/X86/pr38533.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pr38533.ll?rev=339533&view=auto
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/pr38533.ll (added)
> +++ llvm/trunk/test/CodeGen/X86/pr38533.ll Sun Aug 12 22:26:49 2018
> @@ -0,0 +1,11 @@
> +; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
> +; RUN: llc < %s -mtriple=x86_64-unknown | FileCheck %s
> +
> +define void @constant_fold_vector_to_half() {
> +; CHECK-LABEL: constant_fold_vector_to_half:
> +; CHECK:       # %bb.0:
> +; CHECK-NEXT:    movw $16384, (%rax) # imm = 0x4000
> +; CHECK-NEXT:    retq
> +  store volatile half bitcast (<4 x i4> <i4 0, i4 0, i4 0, i4 4> to half), half* undef
> +  ret void
> +}
>
>
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