[llvm] r358017 - [InstCombine] [InstCombine] Canonicalize (-X s/ Y) to -(X s/ Y).

[Roman Lebedev via llvm-commits]

On Tue, Apr 9, 2019 at 7:32 PM Chen Zheng via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
>
> Author: shchenz
> Date: Tue Apr  9 09:34:31 2019
> New Revision: 358017
>
> URL: http://llvm.org/viewvc/llvm-project?rev=358017&view=rev
> Log:
> [InstCombine] [InstCombine] Canonicalize (-X s/ Y) to -(X s/ Y).
>
> Differential Revision: https://reviews.llvm.org/D60395
>
> Modified:
>     llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
>     llvm/trunk/test/Transforms/InstCombine/sdiv-canonicalize.ll
>
> Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp?rev=358017&r1=358016&r2=358017&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp (original)
> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp Tue Apr  9 09:34:31 2019
> @@ -1043,6 +1043,12 @@ Instruction *InstCombiner::visitSDiv(Bin
>        Value *NarrowOp = Builder.CreateSDiv(Op0Src, NarrowDivisor);
>        return new SExtInst(NarrowOp, Op0->getType());
>      }
> +
> +  // -X / Y --> -(X / Y)
> +  Value *Y;
> +  if (match(&I, m_SDiv(m_OneUse(m_NSWSub(m_Zero(), m_Value(X))), m_Value(Y))))
> +    return BinaryOperator::CreateNSWNeg(
> +        Builder.CreateSDiv(X, Y, I.getName(), I.isExact()));
This isn't what i have reviewed and accepted in https://reviews.llvm.org/D60395
In review, this fold was in completely different place of this function.

I can see that Nikita has already reverted the commit, thanks!

Roman.

>      // -X / C --> X / -C (if the negation doesn't overflow).
>      // TODO: This could be enhanced to handle arbitrary vector constants by
>
> Modified: llvm/trunk/test/Transforms/InstCombine/sdiv-canonicalize.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/sdiv-canonicalize.ll?rev=358017&r1=358016&r2=358017&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/InstCombine/sdiv-canonicalize.ll (original)
> +++ llvm/trunk/test/Transforms/InstCombine/sdiv-canonicalize.ll Tue Apr  9 09:34:31 2019
> @@ -3,8 +3,8 @@
>
>  define i32 @test_sdiv_canonicalize_op0(i32 %x, i32 %y) {
>  ; CHECK-LABEL: @test_sdiv_canonicalize_op0(
> -; CHECK-NEXT:    [[NEG:%.*]] = sub nsw i32 0, [[X:%.*]]
> -; CHECK-NEXT:    [[SDIV:%.*]] = sdiv i32 [[NEG]], [[Y:%.*]]
> +; CHECK-NEXT:    [[SDIV1:%.*]] = sdiv i32 [[X:%.*]], [[Y:%.*]]
> +; CHECK-NEXT:    [[SDIV:%.*]] = sub nsw i32 0, [[SDIV1]]
>  ; CHECK-NEXT:    ret i32 [[SDIV]]
>  ;
>    %neg = sub nsw i32 0, %x
> @@ -14,8 +14,8 @@ define i32 @test_sdiv_canonicalize_op0(i
>
>  define i32 @test_sdiv_canonicalize_op0_exact(i32 %x, i32 %y) {
>  ; CHECK-LABEL: @test_sdiv_canonicalize_op0_exact(
> -; CHECK-NEXT:    [[NEG:%.*]] = sub nsw i32 0, [[X:%.*]]
> -; CHECK-NEXT:    [[SDIV:%.*]] = sdiv exact i32 [[NEG]], [[Y:%.*]]
> +; CHECK-NEXT:    [[SDIV1:%.*]] = sdiv exact i32 [[X:%.*]], [[Y:%.*]]
> +; CHECK-NEXT:    [[SDIV:%.*]] = sub nsw i32 0, [[SDIV1]]
>  ; CHECK-NEXT:    ret i32 [[SDIV]]
>  ;
>    %neg = sub nsw i32 0, %x
> @@ -23,6 +23,7 @@ define i32 @test_sdiv_canonicalize_op0_e
>    ret i32 %sdiv
>  }
>
> +; (X/-Y) is not equal to -(X/Y), don't canonicalize.
>  define i32 @test_sdiv_canonicalize_op1(i32 %x, i32 %z) {
>  ; CHECK-LABEL: @test_sdiv_canonicalize_op1(
>  ; CHECK-NEXT:    [[Y:%.*]] = mul i32 [[Z:%.*]], 3
> @@ -49,8 +50,8 @@ define i32 @test_sdiv_canonicalize_nonsw
>
>  define <2 x i32> @test_sdiv_canonicalize_vec(<2 x i32> %x, <2 x i32> %y) {
>  ; CHECK-LABEL: @test_sdiv_canonicalize_vec(
> -; CHECK-NEXT:    [[NEG:%.*]] = sub nsw <2 x i32> zeroinitializer, [[X:%.*]]
> -; CHECK-NEXT:    [[SDIV:%.*]] = sdiv <2 x i32> [[NEG]], [[Y:%.*]]
> +; CHECK-NEXT:    [[SDIV1:%.*]] = sdiv <2 x i32> [[X:%.*]], [[Y:%.*]]
> +; CHECK-NEXT:    [[SDIV:%.*]] = sub nsw <2 x i32> zeroinitializer, [[SDIV1]]
>  ; CHECK-NEXT:    ret <2 x i32> [[SDIV]]
>  ;
>    %neg = sub nsw <2 x i32> <i32 0, i32 0>, %x
> @@ -71,9 +72,8 @@ define i32 @test_sdiv_canonicalize_multi
>    ret i32 %sdiv2
>  }
>
> -; There is combination: (X/-CE) -> -(X/CE)
> -; There is another combination: -(X/CE) -> (X/-CE)
> -; Make sure don't combine them endless.
> +; There is combination: -(X/CE) -> (X/-CE).
> +; If combines (X/-CE) to -(X/CE), make sure don't combine them endless.
>
>  @X = global i32 5
>
>
>
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