Disable indvars on loops when LoopSimplify form is not available.

This fixes PR7333.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106267 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 11 insertions, 0 deletions

diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp
index 36bea67..84e393f 100644
--- a/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -467,6 +467,17 @@ void IndVarSimplify::EliminateIVRemainders() {
 }
 
 bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
+  // If LoopSimplify form is not available, stay out of trouble. Some notes:
+  //  - LSR currently only supports LoopSimplify-form loops. Indvars'
+  //    canonicalization can be a pessimization without LSR to "clean up"
+  //    afterwards.
+  //  - We depend on having a preheader; in particular,
+  //    Loop::getCanonicalInductionVariable only supports loops with preheaders,
+  //    and we're in trouble if we can't find the induction variable even when
+  //    we've manually inserted one.
+  if (!L->isLoopSimplifyForm())
+    return false;
+
   IU = &getAnalysis<IVUsers>();
   LI = &getAnalysis<LoopInfo>();
   SE = &getAnalysis<ScalarEvolution>();