[llvm] r272703 - [ValueTracking] Calls to @llvm.assume always return

[Sanjoy Das via llvm-commits]

Forgot to mention in the commit message: this regression was
introduced in http://reviews.llvm.org/rL272489

On Tue, Jun 14, 2016 at 1:23 PM, Sanjoy Das via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: sanjoy
> Date: Tue Jun 14 15:23:16 2016
> New Revision: 272703
>
> URL: http://llvm.org/viewvc/llvm-project?rev=272703&view=rev
> Log:
> [ValueTracking] Calls to @llvm.assume always return
>
> This change teaches llvm::isGuaranteedToTransferExecutionToSuccessor
> that calls to @llvm.assume always terminate.  Most other relevant
> intrinsics should be covered by the "CS.onlyReadsMemory() ||
> CS.onlyAccessesArgMemory()" bit but we were missing @llvm.assumes
> because we state that it clobbers memory.
>
> Added an LICM test case, but this change is not specific to LICM.
>
> Modified:
>     llvm/trunk/lib/Analysis/ValueTracking.cpp
>     llvm/trunk/test/Transforms/LICM/assume.ll
>
> Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=272703&r1=272702&r2=272703&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
> +++ llvm/trunk/lib/Analysis/ValueTracking.cpp Tue Jun 14 15:23:16 2016
> @@ -3478,7 +3478,8 @@ bool llvm::isGuaranteedToTransferExecuti
>      // but it's consistent with other passes. See http://llvm.org/PR965 .
>      // FIXME: This isn't aggressive enough; a call which only writes to a
>      // global is guaranteed to return.
> -    return CS.onlyReadsMemory() || CS.onlyAccessesArgMemory();
> +    return CS.onlyReadsMemory() || CS.onlyAccessesArgMemory() ||
> +           match(I, m_Intrinsic<Intrinsic::assume>());
>    }
>
>    // Other instructions return normally.
>
> Modified: llvm/trunk/test/Transforms/LICM/assume.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LICM/assume.ll?rev=272703&r1=272702&r2=272703&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/LICM/assume.ll (original)
> +++ llvm/trunk/test/Transforms/LICM/assume.ll Tue Jun 14 15:23:16 2016
> @@ -1,6 +1,7 @@
>  ; RUN: opt -licm -basicaa < %s -S | FileCheck %s
>
> -define void @f(i1 %p) nounwind ssp {
> +define void @f_0(i1 %p) nounwind ssp {
> +; CHECK-LABEL: @f_0(
>  entry:
>    br label %for.body
>
> @@ -31,4 +32,20 @@ for.end104:
>    ret void
>  }
>
> +define void @f_1(i1 %cond, i32* %ptr) {
> +; CHECK-LABEL: @f_1(
> +; CHECK: %val = load i32, i32* %ptr
> +; CHECK-NEXT:  br label %loop
> +
> +entry:
> +  br label %loop
> +
> +loop:
> +  %x = phi i32 [ 0, %entry ], [ %x.inc, %loop ]
> +  call void @llvm.assume(i1 %cond)
> +  %val = load i32, i32* %ptr
> +  %x.inc = add i32 %x, %val
> +  br label %loop
> +}
> +
>  declare void @llvm.assume(i1)
>
>
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-- 
Sanjoy Das
http://playingwithpointers.com