LoopVectorizer: Fix an endless loop in the code that looks for reductions.

The bug was in the code that detects PHIs in if-then-else block sequence.

PR14701.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171008 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp
index 1d78fac500daa20c517b9e3237619ed74f782b1f..20bcf8681b8d6bc883897d83dd6cc7a16ce8b800 100644 (file)
--- a/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -1737,10 +1737,9 @@ bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
   Instruction *ExitInstruction = 0;
 
   // Iter is our iterator. We start with the PHI node and scan for all of the
-  // users of this instruction. All users must be instructions which can be
+  // users of this instruction. All users must be instructions that can be
   // used as reduction variables (such as ADD). We may have a single
-  // out-of-block user. They cycle must end with the original PHI.
-  // Also, we can't have multiple block-local users.
+  // out-of-block user. The cycle must end with the original PHI.
   Instruction *Iter = Phi;
   while (true) {
     // If the instruction has no users then this is a broken
@@ -1752,9 +1751,9 @@ bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
     if (!isReductionInstr(Iter, Kind))
       return false;
 
-    // Did we find a user inside this block ?
+    // Did we find a user inside this loop already ?
     bool FoundInBlockUser = false;
-    // Did we reach the initial PHI node ?
+    // Did we reach the initial PHI node already ?
     bool FoundStartPHI = false;
 
     // For each of the *users* of iter.
@@ -1779,8 +1778,10 @@ bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
       // We allow in-loop PHINodes which are not the original reduction PHI
       // node. If this PHI is the only user of Iter (happens in IF w/ no ELSE
       // structure) then don't skip this PHI.
-      if (isa<PHINode>(U) && U->getParent() != TheLoop->getHeader() &&
-          TheLoop->contains(U) && Iter->getNumUses() > 1)
+      if (isa<PHINode>(Iter) && isa<PHINode>(U) &&
+          U->getParent() != TheLoop->getHeader() &&
+          TheLoop->contains(U) &&
+          Iter->getNumUses() > 1)
         continue;
 
       // We can't have multiple inside users.

diff --git a/test/Transforms/LoopVectorize/2012-10-20-infloop.ll b/test/Transforms/LoopVectorize/2012-10-20-infloop.ll
index 0176c9a18966637a583b95131e9f6120d19746d5..da1abc61fa3cd25a856750c092eb1cb470c61603 100644 (file)
--- a/test/Transforms/LoopVectorize/2012-10-20-infloop.ll
+++ b/test/Transforms/LoopVectorize/2012-10-20-infloop.ll
@@ -25,3 +25,47 @@ for.body:                                         ; preds = %for.body, %entry
 for.end:                                          ; preds = %for.body
  unreachable
 }
+
+;PR14701
+define void @start_model_rare() nounwind uwtable ssp {
+entry:
+  br i1 undef, label %return, label %if.end
+
+if.end:                                           ; preds = %entry
+  br i1 undef, label %cond.false, label %cond.true
+
+cond.true:                                        ; preds = %if.end
+  unreachable
+
+cond.false:                                       ; preds = %if.end
+  br i1 undef, label %cond.false28, label %cond.true20
+
+cond.true20:                                      ; preds = %cond.false
+  unreachable
+
+cond.false28:                                     ; preds = %cond.false
+  br label %for.body40
+
+for.body40:                                       ; preds = %for.inc50, %cond.false28
+  %indvars.iv123 = phi i64 [ 3, %cond.false28 ], [ %indvars.iv.next124, %for.inc50 ]
+  %step.0121 = phi i32 [ 1, %cond.false28 ], [ %step.1, %for.inc50 ]
+  br i1 undef, label %if.then46, label %for.inc50
+
+if.then46:                                        ; preds = %for.body40
+  %inc47 = add nsw i32 %step.0121, 1
+  br label %for.inc50
+
+for.inc50:                                        ; preds = %if.then46, %for.body40
+  %k.1 = phi i32 [ undef, %for.body40 ], [ %inc47, %if.then46 ]
+  %step.1 = phi i32 [ %step.0121, %for.body40 ], [ %inc47, %if.then46 ]
+  %indvars.iv.next124 = add i64 %indvars.iv123, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next124 to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, 256
+  br i1 %exitcond, label %for.end52, label %for.body40
+
+for.end52:                                        ; preds = %for.inc50
+  unreachable
+
+return:                                           ; preds = %entry
+  ret void
+}