Add -verify-indvars for imperfect SCEV trip count verification after indvars.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139169 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 1 deletions

diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp
index b12a76acf8..636fefaf22 100644
--- a/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -76,6 +76,13 @@ namespace llvm {
   cl::opt<bool> DisableIVRewrite(
     "disable-iv-rewrite", cl::Hidden,
     cl::desc("Disable canonical induction variable rewriting"));
+
+  // Trip count verification can be enabled by default under NDEBUG if we
+  // implement a strong expression equivalence checker in SCEV. Until then, we
+  // use the verify-indvars flag, which may assert in some cases.
+  cl::opt<bool> VerifyIndvars(
+    "verify-indvars", cl::Hidden,
+    cl::desc("Verify the ScalarEvolution result after running indvars"));
 }
 
 // Temporary flag for use with -disable-iv-rewrite to force a canonical IV for
@@ -1968,7 +1975,8 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
   // Verify that LFTR, and any other change have not interfered with SCEV's
   // ability to compute trip count.
 #ifndef NDEBUG
-  if (DisableIVRewrite && !isa<SCEVCouldNotCompute>(BackedgeTakenCount)) {
+  if (DisableIVRewrite && VerifyIndvars &&
+      !isa<SCEVCouldNotCompute>(BackedgeTakenCount)) {
     SE->forgetLoop(L);
     const SCEV *NewBECount = SE->getBackedgeTakenCount(L);
     if (SE->getTypeSizeInBits(BackedgeTakenCount->getType()) <