[llvm] r293058 - [InstCombine] Canonicalize guards for AND condition

[Sanjoy Das via llvm-commits]

Hi,

I had to revert these changes in https://reviews.llvm.org/rL293227
since they're buggy around guard intrinsics carrying extra arguments.
I have an example in the commit message for the revert commit.

Thinking about this a bit, I'm also not convinced of the utility
of (2) and (3) in PR31520.  InstCombine does the same canonicalization
for assumes, but there is a fundamental difference between guards and
assumes: assumes do not imply a runtime check of any form, and
complicated expressions feeding into an assumes makes it difficult to
compute the set of ephemeral values.  However, values feeding into a
guard are not ephemeral and the same reasoning does not apply.  In
fact, the extra uses of deopt state inserted by duplicating guards may
actually be a pessimization (since certain InstCombine optimizations
kick in if there is only one use of a value).

-- Sanjoy

On Wed, Jan 25, 2017 at 6:20 AM, Artur Pilipenko via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: apilipenko
> Date: Wed Jan 25 08:20:52 2017
> New Revision: 293058
>
> URL: http://llvm.org/viewvc/llvm-project?rev=293058&view=rev
> Log:
> [InstCombine] Canonicalize guards for AND condition
>
> This is a partial fix for Bug 31520 - [guards] canonicalize guards in instcombine
>
> Reviewed By: apilipenko
>
> Differential Revision: https://reviews.llvm.org/D29074
>
> Patch by Maxim Kazantsev.
>
> Modified:
>     llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
>     llvm/trunk/test/Transforms/InstCombine/call-guard.ll
>
> Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp?rev=293058&r1=293057&r2=293058&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Wed Jan 25 08:20:52 2017
> @@ -2878,6 +2878,23 @@ Instruction *InstCombiner::visitCallInst
>      if (match(II->getNextNode(),
>                m_Intrinsic<Intrinsic::experimental_guard>(m_Specific(IIOperand))))
>        return eraseInstFromFunction(*II);
> +
> +    // Canonicalize guard(a && b) -> guard(a); guard(b);
> +    // Note: New guard intrinsics created here are registered by
> +    // the InstCombineIRInserter object.
> +    Function *GuardIntrinsic = II->getCalledFunction();
> +    Value *A, *B;
> +    OperandBundleDef DeoptOB(*II->getOperandBundle(LLVMContext::OB_deopt));
> +    if (match(IIOperand, m_And(m_Value(A), m_Value(B)))) {
> +      CallInst *GuardA =
> +          Builder->CreateCall(GuardIntrinsic, A, {DeoptOB}, II->getName());
> +      CallInst *GuardB =
> +          Builder->CreateCall(GuardIntrinsic, B, {DeoptOB}, II->getName());
> +      auto CC = II->getCallingConv();
> +      GuardA->setCallingConv(CC);
> +      GuardB->setCallingConv(CC);
> +      return eraseInstFromFunction(*II);
> +    }
>      break;
>    }
>    }
>
> Modified: llvm/trunk/test/Transforms/InstCombine/call-guard.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/call-guard.ll?rev=293058&r1=293057&r2=293058&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/InstCombine/call-guard.ll (original)
> +++ llvm/trunk/test/Transforms/InstCombine/call-guard.ll Wed Jan 25 08:20:52 2017
> @@ -28,3 +28,23 @@ define void @test_guard_adjacent_neg(i1
>    call void(i1, ...) @llvm.experimental.guard( i1 %B )[ "deopt"() ]
>    ret void
>  }
> +
> +define void @test_guard_and(i1 %A, i1 %B) {
> +; CHECK-LABEL: @test_guard_and(
> +; CHECK-NEXT:    call void (i1, ...) @llvm.experimental.guard(i1 %A) [ "deopt"() ]
> +; CHECK-NEXT:    call void (i1, ...) @llvm.experimental.guard(i1 %B) [ "deopt"() ]
> +; CHECK-NEXT:    ret void
> +  %C = and i1 %A, %B
> +  call void(i1, ...) @llvm.experimental.guard( i1 %C )[ "deopt"() ]
> +  ret void
> +}
> +
> +define void @test_guard_and_non_default_cc(i1 %A, i1 %B) {
> +; CHECK-LABEL: @test_guard_and_non_default_cc(
> +; CHECK-NEXT:    call cc99 void (i1, ...) @llvm.experimental.guard(i1 %A) [ "deopt"() ]
> +; CHECK-NEXT:    call cc99 void (i1, ...) @llvm.experimental.guard(i1 %B) [ "deopt"() ]
> +; CHECK-NEXT:    ret void
> +  %C = and i1 %A, %B
> +  call cc99 void(i1, ...) @llvm.experimental.guard( i1 %C )[ "deopt"() ]
> +  ret void
> +}
>
>
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