BBVectorize: Only some insert element operand pairs are free.

This fixes another infinite recursion case when using target costs.
We can only replace insert element input chains that are pure (end
with inserting into an undef).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167784 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 13 deletions

diff --git a/lib/Transforms/Vectorize/BBVectorize.cpp b/lib/Transforms/Vectorize/BBVectorize.cpp
index fb31d91801..32a37bad7f 100644
--- a/lib/Transforms/Vectorize/BBVectorize.cpp
+++ b/lib/Transforms/Vectorize/BBVectorize.cpp
@@ -677,6 +677,19 @@ assert(n < 10 && "hrmm, really?");
 
       return false;
     }
+
+    bool isPureIEChain(InsertElementInst *IE) {
+      InsertElementInst *IENext = IE;
+      do {
+        if (!isa<UndefValue>(IENext->getOperand(0)) &&
+            !isa<InsertElementInst>(IENext->getOperand(0))) {
+          return false;
+        }
+      } while ((IENext =
+                 dyn_cast<InsertElementInst>(IENext->getOperand(0))));
+
+      return true;
+    }
   };
 
   // This function implements one vectorization iteration on the provided
@@ -1854,7 +1867,9 @@ assert(n < 10 && "hrmm, really?");
               // folded with other operations.
               if (Ty1 == Ty2) {
                 // If both are insert elements, then both can be widened.
-                if (isa<InsertElementInst>(O1) && isa<InsertElementInst>(O2))
+                InsertElementInst *IEO1 = dyn_cast<InsertElementInst>(O1),
+                                  *IEO2 = dyn_cast<InsertElementInst>(O2);
+                if (IEO1 && IEO2 && isPureIEChain(IEO1) && isPureIEChain(IEO2))
                   continue;
                 // If both are extract elements, and both have the same input
                 // type, then they can be replaced with a shuffle
@@ -2126,18 +2141,7 @@ assert(n < 10 && "hrmm, really?");
     if (InsertElementInst *LIE = dyn_cast<InsertElementInst>(LOp)) {
       // If we have a pure insertelement chain, then this can be rewritten
       // into a chain that directly builds the larger type.
-      bool PureChain = true;
-      InsertElementInst *LIENext = LIE;
-      do {
-        if (!isa<UndefValue>(LIENext->getOperand(0)) &&
-            !isa<InsertElementInst>(LIENext->getOperand(0))) {
-          PureChain = false;
-          break;
-        }
-      } while ((LIENext =
-                 dyn_cast<InsertElementInst>(LIENext->getOperand(0))));
-
-      if (PureChain) {
+      if (isPureIEChain(LIE)) {
         SmallVector<Value *, 8> VectElemts(numElemL,
           UndefValue::get(ArgTypeL->getScalarType()));
         InsertElementInst *LIENext = LIE;