[llvm] r296759 - Re-apply "[GVNHoist] Move GVNHoist to function simplification part of pipeline."

[Benjamin Kramer via llvm-commits]

This miscompiles bash. Self-contained test-case attached (produces
different output at -O2 before and after this patch). Reverted in
r296872.

On Thu, Mar 2, 2017 at 5:16 PM, Geoff Berry via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: gberry
> Date: Thu Mar  2 10:16:47 2017
> New Revision: 296759
>
> URL: http://llvm.org/viewvc/llvm-project?rev=296759&view=rev
> Log:
> Re-apply "[GVNHoist] Move GVNHoist to function simplification part of pipeline."
>
> This re-applies r289696, which caused TSan perf regression, which has
> since been addressed in separate changes (see PR for details).
>
> See PR31382.
>
> Added:
>     llvm/trunk/test/Transforms/GVNHoist/hoist-inline.ll
> Modified:
>     llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp
>
> Modified: llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp?rev=296759&r1=296758&r2=296759&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp (original)
> +++ llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp Thu Mar  2 10:16:47 2017
> @@ -244,8 +244,6 @@ void PassManagerBuilder::populateFunctio
>    FPM.add(createCFGSimplificationPass());
>    FPM.add(createSROAPass());
>    FPM.add(createEarlyCSEPass());
> -  if(EnableGVNHoist)
> -    FPM.add(createGVNHoistPass());
>    FPM.add(createLowerExpectIntrinsicPass());
>  }
>
> @@ -290,6 +288,8 @@ void PassManagerBuilder::addFunctionSimp
>    // Break up aggregate allocas, using SSAUpdater.
>    MPM.add(createSROAPass());
>    MPM.add(createEarlyCSEPass());              // Catch trivial redundancies
> +  if(EnableGVNHoist)
> +    MPM.add(createGVNHoistPass());
>    // Speculative execution if the target has divergent branches; otherwise nop.
>    MPM.add(createSpeculativeExecutionIfHasBranchDivergencePass());
>    MPM.add(createJumpThreadingPass());         // Thread jumps.
>
> Added: llvm/trunk/test/Transforms/GVNHoist/hoist-inline.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVNHoist/hoist-inline.ll?rev=296759&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/GVNHoist/hoist-inline.ll (added)
> +++ llvm/trunk/test/Transforms/GVNHoist/hoist-inline.ll Thu Mar  2 10:16:47 2017
> @@ -0,0 +1,38 @@
> +; RUN: opt -S -O2 < %s | FileCheck %s
> +
> +; Check that the inlined loads are hoisted.
> +; CHECK-LABEL: define i32 @fun(
> +; CHECK-LABEL: entry:
> +; CHECK: load i32, i32* @A
> +; CHECK: if.then:
> +
> + at A = external global i32
> + at B = external global i32
> + at C = external global i32
> +
> +define i32 @loadA() {
> +   %a = load i32, i32* @A
> +   ret i32 %a
> +}
> +
> +define i32 @fun(i1 %c) {
> +entry:
> +  br i1 %c, label %if.then, label %if.else
> +
> +if.then:
> +  store i32 1, i32* @B
> +  %call1 = call i32 @loadA()
> +  store i32 2, i32* @C
> +  br label %if.endif
> +
> +if.else:
> +  store i32 2, i32* @C
> +  %call2 = call i32 @loadA()
> +  store i32 1, i32* @B
> +  br label %if.endif
> +
> +if.endif:
> +  %ret = phi i32 [ %call1, %if.then ], [ %call2, %if.else ]
> +  ret i32 %ret
> +}
> +
>
>
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