patch for alp vectorizer assert

[Arnold]

LGTM. Please commit.

Thanks.

> On Feb 16, 2014, at 6:42 PM, Gerolf Hoflehner <ghoflehner at apple.com> wrote:
> 
> Hi
> 
> We run into an  null VectorizedValue assertion in the SLP Vectorizer (in function vectorizeTree()). The root cause is that we can end up picking wrong PHI nodes because we used 
> indices to get their incoming value rather than the  blocks.
> 
> 
> -Gerolf
> 
> <slp.patch>
> 
> 
> 
> 
> 
> Index: lib/Transforms/Vectorize/SLPVectorizer.cpp
> ===================================================================
> --- lib/Transforms/Vectorize/SLPVectorizer.cpp	(revision 201486)
> +++ lib/Transforms/Vectorize/SLPVectorizer.cpp	(working copy)
> @@ -779,7 +779,8 @@
>        // Check for terminator values (e.g. invoke).
>        for (unsigned j = 0; j < VL.size(); ++j)
>          for (unsigned i = 0, e = PH->getNumIncomingValues(); i < e; ++i) {
> -          TerminatorInst *Term = dyn_cast<TerminatorInst>(cast<PHINode>(VL[j])->getIncomingValue(i));
> +          TerminatorInst *Term = dyn_cast<TerminatorInst>(
> +              cast<PHINode>(VL[j])->getIncomingValueForBlock(PH->getIncomingBlock(i)));
>            if (Term) {
>              DEBUG(dbgs() << "SLP: Need to swizzle PHINodes (TerminatorInst use).\n");
>              newTreeEntry(VL, false);
> @@ -794,7 +795,8 @@
>          ValueList Operands;
>          // Prepare the operand vector.
>          for (unsigned j = 0; j < VL.size(); ++j)
> -          Operands.push_back(cast<PHINode>(VL[j])->getIncomingValue(i));
> +          Operands.push_back(cast<PHINode>(VL[j])->getIncomingValueForBlock(
> +              PH->getIncomingBlock(i)));
>  
>          buildTree_rec(Operands, Depth + 1);
>        }
> Index: test/Transforms/SLPVectorizer/X86/crash_vectorizeTree.ll
> ===================================================================
> --- test/Transforms/SLPVectorizer/X86/crash_vectorizeTree.ll	(revision 0)
> +++ test/Transforms/SLPVectorizer/X86/crash_vectorizeTree.ll	(working copy)
> @@ -0,0 +1,65 @@
> +; RUN: opt -slp-vectorizer -mtriple=x86_64-apple-macosx10.9.0 -mcpu=corei7-avx -S < %s | FileCheck %s
> +target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
> +target triple = "x86_64-apple-macosx10.9.0"
> +
> +
> +; This test used to crash because we were following phi chains incorrectly.
> +; We used indices to get the incoming value of two phi nodes rather than 
> +; incoming block lookup.
> +; This can give wrong results when the ordering of incoming
> +; edges in the two phi nodes don't match.
> +;CHECK-LABEL: bar
> +
> +%0 = type { %1, %2 }
> +%1 = type { double, double }
> +%2 = type { double, double }
> +
> +
> +;define fastcc void @bar() {
> +define void @bar() {
> +  %1 = getelementptr inbounds %0* undef, i64 0, i32 1, i32 0
> +  %2 = getelementptr inbounds %0* undef, i64 0, i32 1, i32 1
> +  %3 = getelementptr inbounds %0* undef, i64 0, i32 1, i32 0
> +  %4 = getelementptr inbounds %0* undef, i64 0, i32 1, i32 1
> +  %5 = getelementptr inbounds %0* undef, i64 0, i32 1, i32 0
> +  %6 = getelementptr inbounds %0* undef, i64 0, i32 1, i32 1
> +  br label %7
> +
> +; <label>:7                                       ; preds = %18, %17, %17, %0
> +  %8 = phi double [ 2.800000e+01, %0 ], [ %11, %18 ], [ %11, %17 ], [ %11, %17 ]
> +  %9 = phi double [ 1.800000e+01, %0 ], [ %10, %18 ], [ %10, %17 ], [ %10, %17 ]
> +  store double %9, double* %1, align 8
> +  store double %8, double* %2, align 8
> +  %10 = load double* %3, align 8
> +  %11 = load double* %4, align 8
> +  br i1 undef, label %12, label %13
> +
> +; <label>:12                                      ; preds = %7
> +  ret void
> +
> +; <label>:13                                      ; preds = %7
> +  store double %10, double* %5, align 8
> +  store double %11, double* %6, align 8
> +  br i1 undef, label %14, label %15
> +
> +; <label>:14                                      ; preds = %13
> +  br label %15
> +
> +; <label>:15                                      ; preds = %14, %13
> +  br i1 undef, label %16, label %17
> +
> +; <label>:16                                      ; preds = %15
> +  unreachable
> +
> +; <label>:17                                      ; preds = %15
> +  switch i32 undef, label %18 [
> +    i32 32, label %7
> +    i32 103, label %7
> +  ]
> +
> +; <label>:18                                      ; preds = %17
> +  br i1 undef, label %7, label %19
> +
> +; <label>:19                                      ; preds = %18
> +  unreachable
> +}
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