[llvm] 67266d8 - [InstCombine] Negator: shufflevector is negatible

Wed Oct 7 01:56:56 PDT 2020

Hi,

It's been a while since this commit was submitted, but we found a case
that started crashing with it.
I wrote
 https://bugs.llvm.org/show_bug.cgi?id=47752
about the problem.

/Mikael

On Wed, 2020-04-22 at 05:18 -0700, Roman Lebedev via llvm-commits
wrote:
> Author: Roman Lebedev
> Date: 2020-04-22T15:14:23+03:00
> New Revision: 67266d879c715cdcfb790acf0153da757dafd195
> 
> URL: 
> https://protect2.fireeye.com/v1/url?k=75719db2-29a5951b-7571dd29-865b3b1e120b-621911ebddca53bf&q=1&e=7701d29f-693b-472c-b4c6-0865623a2d30&u=https%3A%2F%2Fgithub.com%2Fllvm%2Fllvm-project%2Fcommit%2F67266d879c715cdcfb790acf0153da757dafd195
> DIFF: 
> https://protect2.fireeye.com/v1/url?k=380b870e-64df8fa7-380bc795-865b3b1e120b-da0ff30e46f3356c&q=1&e=7701d29f-693b-472c-b4c6-0865623a2d30&u=https%3A%2F%2Fgithub.com%2Fllvm%2Fllvm-project%2Fcommit%2F67266d879c715cdcfb790acf0153da757dafd195.diff
> 
> LOG: [InstCombine] Negator: shufflevector is negatible
> 
> All these folds are correct as per alive-tv
> 
> Added: 
>     
> 
> Modified: 
>     llvm/lib/Transforms/InstCombine/InstCombineNegator.cpp
>     llvm/test/Transforms/InstCombine/sub-of-negatible.ll
> 
> Removed: 
>     
> 
> 
> #####################################################################
> ###########
> diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineNegator.cpp
> b/llvm/lib/Transforms/InstCombine/InstCombineNegator.cpp
> index 32f37c6d04cf..e119a383e9db 100644
> --- a/llvm/lib/Transforms/InstCombine/InstCombineNegator.cpp
> +++ b/llvm/lib/Transforms/InstCombine/InstCombineNegator.cpp
> @@ -111,6 +111,10 @@ LLVM_NODISCARD Value *Negator::visit(Value *V,
> unsigned Depth) {
>    ++NumValuesVisitedInThisNegator;
>  #endif
>  
> +  // -(undef) -> undef.
> +  if (match(V, m_Undef()))
> +    return V;
> +
>    // In i1, negation can simply be ignored.
>    if (V->getType()->isIntOrIntVectorTy(1))
>      return V;
> @@ -265,6 +269,18 @@ LLVM_NODISCARD Value *Negator::visit(Value *V,
> unsigned Depth) {
>      return Builder.CreateSelect(I->getOperand(0), NegOp1, NegOp2,
>                                  I->getName() + ".neg",
> /*MDFrom=*/I);
>    }
> +  case Instruction::ShuffleVector: {
> +    // `shufflevector` is negatible if both operands are negatible.
> +    ShuffleVectorInst *Shuf = cast<ShuffleVectorInst>(I);
> +    Value *NegOp0 = visit(I->getOperand(0), Depth + 1);
> +    if (!NegOp0) // Early return.
> +      return nullptr;
> +    Value *NegOp1 = visit(I->getOperand(1), Depth + 1);
> +    if (!NegOp1)
> +      return nullptr;
> +    return Builder.CreateShuffleVector(NegOp0, NegOp1, Shuf-
> >getShuffleMask(),
> +                                       I->getName() + ".neg");
> +  }
>    case Instruction::Trunc: {
>      // `trunc` is negatible if its operand is negatible.
>      Value *NegOp = visit(I->getOperand(0), Depth + 1);
> 
> diff  --git a/llvm/test/Transforms/InstCombine/sub-of-negatible.ll
> b/llvm/test/Transforms/InstCombine/sub-of-negatible.ll
> index 21f695f40172..d676c0ba0936 100644
> --- a/llvm/test/Transforms/InstCombine/sub-of-negatible.ll
> +++ b/llvm/test/Transforms/InstCombine/sub-of-negatible.ll
> @@ -625,9 +625,9 @@ define i8 @negate_zext_wrongwidth(i8 %x, i2 %y) {
>  
>  define <2 x i4> @negate_shufflevector_oneinput_reverse(<2 x i4> %x,
> <2 x i4> %y) {
>  ; CHECK-LABEL: @negate_shufflevector_oneinput_reverse(
> -; CHECK-NEXT:    [[T0:%.*]] = shl <2 x i4> <i4 -6, i4 5>, [[X:%.*]]
> -; CHECK-NEXT:    [[T1:%.*]] = shufflevector <2 x i4> [[T0]], <2 x
> i4> undef, <2 x i32> <i32 1, i32 0>
> -; CHECK-NEXT:    [[T2:%.*]] = sub <2 x i4> [[Y:%.*]], [[T1]]
> +; CHECK-NEXT:    [[T0_NEG:%.*]] = shl <2 x i4> <i4 6, i4 -5>,
> [[X:%.*]]
> +; CHECK-NEXT:    [[T1_NEG:%.*]] = shufflevector <2 x i4> [[T0_NEG]],
> <2 x i4> undef, <2 x i32> <i32 1, i32 0>
> +; CHECK-NEXT:    [[T2:%.*]] = add <2 x i4> [[T1_NEG]], [[Y:%.*]]
>  ; CHECK-NEXT:    ret <2 x i4> [[T2]]
>  ;
>    %t0 = shl <2 x i4> <i4 -6, i4 5>, %x
> @@ -637,9 +637,9 @@ define <2 x i4>
> @negate_shufflevector_oneinput_reverse(<2 x i4> %x, <2 x i4> %y)
>  }
>  define <2 x i4>
> @negate_shufflevector_oneinput_second_lane_is_undef(<2 x i4> %x, <2 x
> i4> %y) {
>  ; CHECK-LABEL: @negate_shufflevector_oneinput_second_lane_is_undef(
> -; CHECK-NEXT:    [[T0:%.*]] = shl <2 x i4> <i4 -6, i4 5>, [[X:%.*]]
> -; CHECK-NEXT:    [[T1:%.*]] = shufflevector <2 x i4> [[T0]], <2 x
> i4> undef, <2 x i32> <i32 0, i32 undef>
> -; CHECK-NEXT:    [[T2:%.*]] = sub <2 x i4> [[Y:%.*]], [[T1]]
> +; CHECK-NEXT:    [[T0_NEG:%.*]] = shl <2 x i4> <i4 6, i4 -5>,
> [[X:%.*]]
> +; CHECK-NEXT:    [[T1_NEG:%.*]] = shufflevector <2 x i4> [[T0_NEG]],
> <2 x i4> undef, <2 x i32> <i32 0, i32 undef>
> +; CHECK-NEXT:    [[T2:%.*]] = add <2 x i4> [[T1_NEG]], [[Y:%.*]]
>  ; CHECK-NEXT:    ret <2 x i4> [[T2]]
>  ;
>    %t0 = shl <2 x i4> <i4 -6, i4 5>, %x
> @@ -649,10 +649,10 @@ define <2 x i4>
> @negate_shufflevector_oneinput_second_lane_is_undef(<2 x i4> %x,
>  }
>  define <2 x i4> @negate_shufflevector_twoinputs(<2 x i4> %x, <2 x
> i4> %y, <2 x i4> %z) {
>  ; CHECK-LABEL: @negate_shufflevector_twoinputs(
> -; CHECK-NEXT:    [[T0:%.*]] = shl <2 x i4> <i4 -6, i4 5>, [[X:%.*]]
> -; CHECK-NEXT:    [[T1:%.*]] = xor <2 x i4> [[Y:%.*]], <i4 undef, i4
> -1>
> -; CHECK-NEXT:    [[T2:%.*]] = shufflevector <2 x i4> [[T0]], <2 x
> i4> [[T1]], <2 x i32> <i32 0, i32 3>
> -; CHECK-NEXT:    [[T3:%.*]] = sub <2 x i4> [[Z:%.*]], [[T2]]
> +; CHECK-NEXT:    [[T0_NEG:%.*]] = shl <2 x i4> <i4 6, i4 -5>,
> [[X:%.*]]
> +; CHECK-NEXT:    [[T1_NEG:%.*]] = add <2 x i4> [[Y:%.*]], <i4 undef,
> i4 1>
> +; CHECK-NEXT:    [[T2_NEG:%.*]] = shufflevector <2 x i4> [[T0_NEG]],
> <2 x i4> [[T1_NEG]], <2 x i32> <i32 0, i32 3>
> +; CHECK-NEXT:    [[T3:%.*]] = add <2 x i4> [[T2_NEG]], [[Z:%.*]]
>  ; CHECK-NEXT:    ret <2 x i4> [[T3]]
>  ;
>    %t0 = shl <2 x i4> <i4 -6, i4 5>, %x
> 
> 
>         
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