[llvm] r278913 - Fix bug in DAGBuilder for getelementptr with expanded vector.

[Quentin Colombet via llvm-commits]

Hi Ayman,

I am not seeing a PR related to this (I am not asking for you to create one :)).
But could you comment on:
- When was the problem introduced?
- What does it take to expose it? I.e., what are the different conditions that need to line up for it to show up?
- What is the symptom when the bug is hit? I am guessing miscompile.

In the future, please put that information in the commit message.

Thanks,
-Quentin
> On Aug 17, 2016, at 12:52 AM, Ayman Musa via llvm-commits <llvm-commits at lists.llvm.org> wrote:
> 
> Author: aymanmus
> Date: Wed Aug 17 02:52:15 2016
> New Revision: 278913
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=278913&view=rev
> Log:
> Fix bug in DAGBuilder for getelementptr with expanded vector.
> 
> Replacing the usage of MVT with EVT in case the vector type is expanded.
> Differential Revision: https://reviews.llvm.org/D23306
> 
> Added:
>    llvm/trunk/test/CodeGen/X86/gep-expanded-vector.ll
> Modified:
>    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
> 
> Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp?rev=278913&r1=278912&r2=278913&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
> +++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Wed Aug 17 02:52:15 2016
> @@ -3329,8 +3329,9 @@ void SelectionDAGBuilder::visitGetElemen
>         if (CI->isZero())
>           continue;
>         APInt Offs = ElementSize * CI->getValue().sextOrTrunc(PtrSize);
> +        LLVMContext &Context = *DAG.getContext();
>         SDValue OffsVal = VectorWidth ?
> -          DAG.getConstant(Offs, dl, MVT::getVectorVT(PtrTy, VectorWidth)) :
> +          DAG.getConstant(Offs, dl, EVT::getVectorVT(Context, PtrTy, VectorWidth)) :
>           DAG.getConstant(Offs, dl, PtrTy);
> 
>         // In an inbouds GEP with an offset that is nonnegative even when
> 
> Added: llvm/trunk/test/CodeGen/X86/gep-expanded-vector.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/gep-expanded-vector.ll?rev=278913&view=auto
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/gep-expanded-vector.ll (added)
> +++ llvm/trunk/test/CodeGen/X86/gep-expanded-vector.ll Wed Aug 17 02:52:15 2016
> @@ -0,0 +1,24 @@
> +; RUN: llc < %s -O2 -mattr=avx512f -mtriple=x86_64-unknown | FileCheck %s
> +
> +%struct.S1 = type { %struct.S1*, %struct.S1* }
> +
> +define %struct.S1** @malloc_init_state(<64 x %struct.S1**> %tmp, i32 %ind) {
> +entry:
> +  %Vec = getelementptr inbounds %struct.S1*, <64 x %struct.S1**> %tmp , i64 2
> +  %ptr = extractelement <64 x %struct.S1**> %Vec, i32 %ind
> +  ret %struct.S1** %ptr
> +}
> +
> +; CHECK: .LCPI0_0:
> +; CHECK: .quad 16
> +; CHECK: vpbroadcastq    .LCPI0_0(%rip), [[Z1:%zmm[0-9]]]
> +; CHECK-NEXT: vpaddq  [[Z1]], [[Z2:%zmm[0-9]]], [[Z2]]
> +; CHECK-NEXT: vpaddq  [[Z1]], [[Z3:%zmm[0-9]]], [[Z3]]
> +; CHECK-NEXT: vpaddq  [[Z1]], [[Z4:%zmm[0-9]]], [[Z4]]
> +; CHECK-NEXT: vpaddq  [[Z1]], [[Z5:%zmm[0-9]]], [[Z5]]
> +; CHECK-NEXT: vpaddq  [[Z1]], [[Z6:%zmm[0-9]]], [[Z6]]
> +; CHECK-NEXT: vpaddq  [[Z1]], [[Z7:%zmm[0-9]]], [[Z7]]
> +; CHECK-NEXT: vpaddq  [[Z1]], [[Z8:%zmm[0-9]]], [[Z8]]
> +; CHECK-NEXT: vpaddq  [[Z1]], [[Z9:%zmm[0-9]]], [[Z9]]
> +
> +
> 
> 
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