[llvm] r276181 - [GVNHoist] Don't hoist PHI nodes

[Hans Wennborg via llvm-commits]

Merged to 3.9 in r276418.

On Wed, Jul 20, 2016 at 5:05 PM, David Majnemer via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: majnemer
> Date: Wed Jul 20 16:05:01 2016
> New Revision: 276181
>
> URL: http://llvm.org/viewvc/llvm-project?rev=276181&view=rev
> Log:
> [GVNHoist] Don't hoist PHI nodes
>
> We hoisted PHIs without respecting their special insertion point in the
> block, leading to verfier errors.
>
> This fixes PR28626.
>
> Added:
>     llvm/trunk/test/Transforms/GVN/pr28626.ll
> Modified:
>     llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp
>
> Modified: llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp?rev=276181&r1=276180&r2=276181&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp Wed Jul 20 16:05:01 2016
> @@ -576,16 +576,20 @@ public:
>
>    bool makeOperandsAvailable(Instruction *Repl, BasicBlock *HoistPt) const {
>      // Check whether the GEP of a ld/st can be synthesized at HoistPt.
> -    Instruction *Gep = nullptr;
> +    GetElementPtrInst *Gep = nullptr;
>      Instruction *Val = nullptr;
>      if (auto *Ld = dyn_cast<LoadInst>(Repl))
> -      Gep = dyn_cast<Instruction>(Ld->getPointerOperand());
> +      Gep = dyn_cast<GetElementPtrInst>(Ld->getPointerOperand());
>      if (auto *St = dyn_cast<StoreInst>(Repl)) {
> -      Gep = dyn_cast<Instruction>(St->getPointerOperand());
> +      Gep = dyn_cast<GetElementPtrInst>(St->getPointerOperand());
>        Val = dyn_cast<Instruction>(St->getValueOperand());
>      }
>
> -    if (!Gep || !isa<GetElementPtrInst>(Gep))
> +    if (!Gep)
> +      return false;
> +
> +    // PHIs may only be inserted at the start of a block.
> +    if (Val && isa<PHINode>(Val))
>        return false;
>
>      // Check whether we can compute the Gep at HoistPt.
>
> Added: llvm/trunk/test/Transforms/GVN/pr28626.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVN/pr28626.ll?rev=276181&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/GVN/pr28626.ll (added)
> +++ llvm/trunk/test/Transforms/GVN/pr28626.ll Wed Jul 20 16:05:01 2016
> @@ -0,0 +1,42 @@
> +; RUN: opt -S -gvn-hoist < %s | FileCheck %s
> +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
> +target triple = "x86_64-unknown-linux-gnu"
> +
> +define void @test1(i1 %a, i1** %d) {
> +entry:
> +  %0 = load i1*, i1** %d, align 8
> +  br i1 %a, label %if.then, label %if.else
> +
> +if.then:                                          ; preds = %entry
> +  br label %if.end
> +
> +if.else:                                          ; preds = %entry
> +  br label %if.end
> +
> +if.end:                                           ; preds = %if.else, %if.then
> +  %c.0 = phi i1 [ 1, %if.then ], [ 0, %if.else ]
> +  br i1 %c.0, label %if.then2, label %if.else3
> +
> +if.then2:                                         ; preds = %if.end
> +  %rc = getelementptr inbounds i1, i1* %0, i64 0
> +  store i1 %c.0, i1* %rc, align 4
> +  br label %if.end6
> +
> +if.else3:                                         ; preds = %if.end
> +  %rc5 = getelementptr inbounds i1, i1* %0, i64 0
> +  store i1 %c.0, i1* %rc5, align 4
> +  br label %if.end6
> +
> +if.end6:                                          ; preds = %if.else3, %if.then2
> +  ret void
> +}
> +
> +; CHECK-LABEL: define void @test1(
> +; CHECK:  %[[load:.*]] = load i1*, i1** %d, align 8
> +; CHECK:  %[[phi:.*]] = phi i1 [ true, {{.*}} ], [ false, {{.*}} ]
> +
> +; CHECK: %[[gep0:.*]] = getelementptr inbounds i1, i1* %[[load]], i64 0
> +; CHECK: store i1 %[[phi]], i1* %[[gep0]], align 4
> +
> +; CHECK: %[[gep1:.*]] = getelementptr inbounds i1, i1* %[[load]], i64 0
> +; CHECK: store i1 %[[phi]], i1* %[[gep1]], align 4
>
>
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