[llvm] r321789 - [GVNHoist] Fix: PR35222 gvn-hoist incorrectly erases load in case of a loop

[Hans Wennborg via llvm-commits]

Merged to 6.0 in r322558.

On Thu, Jan 4, 2018 at 8:47 AM, Aditya Kumar via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: hiraditya
> Date: Wed Jan  3 23:47:24 2018
> New Revision: 321789
>
> URL: http://llvm.org/viewvc/llvm-project?rev=321789&view=rev
> Log:
> [GVNHoist] Fix: PR35222 gvn-hoist incorrectly erases load in case of a loop
>
> Reviewers:
>     dberlin
>     sebpop
>     eli.friedman
>
> Differential Revision: https://reviews.llvm.org/D41453
>
> Modified:
>     llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp
>     llvm/trunk/test/Transforms/GVNHoist/pr35222-hoist-load.ll
>
> Modified: llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp?rev=321789&r1=321788&r2=321789&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp Wed Jan  3 23:47:24 2018
> @@ -648,7 +648,7 @@ private:
>            // track in a CHI. In the PDom walk, there can be values in the
>            // stack which are not control dependent e.g., nested loop.
>            if (si != RenameStack.end() && si->second.size() &&
> -              DT->dominates(Pred, si->second.back()->getParent())) {
> +              DT->properlyDominates(Pred, si->second.back()->getParent())) {
>              C.Dest = BB;                     // Assign the edge
>              C.I = si->second.pop_back_val(); // Assign the argument
>              DEBUG(dbgs() << "\nCHI Inserted in BB: " << C.Dest->getName()
>
> Modified: llvm/trunk/test/Transforms/GVNHoist/pr35222-hoist-load.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVNHoist/pr35222-hoist-load.ll?rev=321789&r1=321788&r2=321789&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/GVNHoist/pr35222-hoist-load.ll (original)
> +++ llvm/trunk/test/Transforms/GVNHoist/pr35222-hoist-load.ll Wed Jan  3 23:47:24 2018
> @@ -1,4 +1,5 @@
>  ; RUN: opt -S -gvn-hoist < %s | FileCheck %s
> +; CHECK-LABEL: build_tree
>  ; CHECK: load
>  ; CHECK: load
>  ; Check that the load is not hoisted because the call can potentially
> @@ -23,3 +24,47 @@ do.end:
>  }
>
>  declare i1 @pqdownheap(i32)
> +
> + at i = external hidden unnamed_addr global i32, align 4
> + at j = external hidden unnamed_addr global [573 x i32], align 4
> + at v = external global i1
> +
> +; CHECK-LABEL: test
> +; CHECK-LABEL: do.end
> +; CHECK: load
> +; Check that the load is not hoisted because the call can potentially
> +; modify the global
> +
> +define i32 @test() {
> +entry:
> +  br label %for.cond
> +
> +for.cond:
> +  %a3 = load volatile i1, i1* @v
> +  br i1 %a3, label %for.body, label %while.end
> +
> +for.body:
> +  br label %if.then
> +
> +if.then:
> +  %tmp4 = load i32, i32* @i, align 4
> +  br label %for.cond
> +
> +while.end:
> +  br label %do.body
> +
> +do.body:
> +  %tmp9 = load i32, i32* getelementptr inbounds ([573 x i32], [573 x i32]* @j,
> +i32 0, i32 1), align 4
> +  %tmp10 = load i32, i32* @i, align 4
> +  call void @fn()
> +  %a1 = load volatile i1, i1* @v
> +  br i1 %a1, label %do.body, label %do.end
> +
> +do.end:
> +  %tmp20 = load i32, i32* getelementptr inbounds ([573 x i32], [573 x i32]* @j,
> +i32 0, i32 1), align 4
> +  ret i32 %tmp20
> +}
> +
> +declare void @fn()
>
>
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