Even if there are not any induction variables in the loop, if we can compute

the trip count for the loop, insert one so that we can canonicalize the exit
condition.

llvm-svn: 13015

1 files changed, 11 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
index 9bc897fe022..fa81f81f743 100644
--- a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -368,7 +368,17 @@ void IndVarSimplify::runOnLoop(Loop *L) {
 
   // If there are no induction variables in the loop, there is nothing more to
   // do.
-  if (IndVars.empty()) return;
+  if (IndVars.empty()) {
+    // Actually, if we know how many times the loop iterates, lets insert a
+    // canonical induction variable to help subsequent passes.
+    if (!isa<SCEVCouldNotCompute>(IterationCount)) {
+      ScalarEvolutionRewriter Rewriter(*SE, *LI);
+      Rewriter.GetOrInsertCanonicalInductionVariable(L,
+                                                     IterationCount->getType());
+      LinearFunctionTestReplace(L, IterationCount, Rewriter);
+    }
+    return;
+  }
 
   // Compute the type of the largest recurrence expression.
   //