LoopVectorizer: Fix a bug in the code that updates the loop exiting block.

LCSSA PHIs may have undef values. The vectorizer updates values that are used by outside users such as PHIs.
The bug happened because undefs are not loop values. This patch handles these PHIs.

PR14725



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171251 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 42 insertions, 0 deletions

diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp
index 7fb9bbada0..653c111182 100644
--- a/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -909,6 +909,19 @@ InnerLoopVectorizer::vectorizeLoop(LoopVectorizationLegality *Legal) {
     (RdxPhi)->setIncomingValue(SelfEdgeBlockIdx, Scalar0);
     (RdxPhi)->setIncomingValue(IncomingEdgeBlockIdx, RdxDesc.LoopExitInstr);
   }// end of for each redux variable.
+
+  // The Loop exit block may have single value PHI nodes where the incoming
+  // value is 'undef'. While vectorizing we only handled real values that
+  // were defined inside the loop. Here we handle the 'undef case'.
+  // See PR14725.
+  for (BasicBlock::iterator LEI = LoopExitBlock->begin(),
+       LEE = LoopExitBlock->end(); LEI != LEE; ++LEI) {
+    PHINode *LCSSAPhi = dyn_cast<PHINode>(LEI);
+    if (!LCSSAPhi) continue;
+    if (LCSSAPhi->getNumIncomingValues() == 1)
+      LCSSAPhi->addIncoming(UndefValue::get(LCSSAPhi->getType()),
+                            LoopMiddleBlock);
+  }
 }
 
 Value *InnerLoopVectorizer::createEdgeMask(BasicBlock *Src, BasicBlock *Dst) {
diff --git a/test/Transforms/LoopVectorize/lcssa-crash.ll b/test/Transforms/LoopVectorize/lcssa-crash.ll
new file mode 100644
index 0000000000..a618db53ff
--- /dev/null
+++ b/test/Transforms/LoopVectorize/lcssa-crash.ll
@@ -0,0 +1,29 @@
+; RUN: opt < %s  -loop-vectorize -force-vector-width=4 
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%type1 = type { %type2 }
+%type2 = type { [0 x i8*], i8**, i32, i32, i32 }
+
+define void @test() nounwind uwtable align 2 {
+  br label %for.body.lr.ph.i.i.i
+
+for.body.lr.ph.i.i.i:
+  br label %for.body.i.i.i
+
+for.body.i.i.i:
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.inc.i.i.i ], [ 0, %for.body.lr.ph.i.i.i ]
+  br label %for.inc.i.i.i
+
+for.inc.i.i.i:
+  %indvars.iv.next = add i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp ne i32 %lftr.wideiv, undef
+  br i1 %exitcond, label %for.body.i.i.i, label %for.end.i.i.i
+
+for.end.i.i.i:
+  %lcssa = phi %type1* [ undef, %for.inc.i.i.i ]
+  unreachable
+}
+