patch for alp vectorizer assert

[Gerolf Hoflehner]

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







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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