Restore the LoopInstSimplify pass, reverting r327329 that removed it.

The plan had always been to move towards using this rather than so much
in-pass simplification within the loop pipeline, but we never got around
to it.... until only a couple months after it was removed due to disuse.
=/

This commit is just a pure revert of the removal. I will add tests and
do some basic cleanup in follow-up commits. Then I'll wire it into the
loop pass pipeline.

Differential Revision: https://reviews.llvm.org/D47353

llvm-svn: 333250

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
index 4787e70bbb1..8b9962af38c 100644
--- a/llvm/lib/Passes/PassBuilder.cpp
+++ b/llvm/lib/Passes/PassBuilder.cpp
@@ -111,6 +111,7 @@
 #include "llvm/Transforms/Scalar/LoopDeletion.h"
 #include "llvm/Transforms/Scalar/LoopDistribute.h"
 #include "llvm/Transforms/Scalar/LoopIdiomRecognize.h"
+#include "llvm/Transforms/Scalar/LoopInstSimplify.h"
 #include "llvm/Transforms/Scalar/LoopLoadElimination.h"
 #include "llvm/Transforms/Scalar/LoopPassManager.h"
 #include "llvm/Transforms/Scalar/LoopPredication.h"
@@ -391,8 +392,9 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
   // FIXME: Currently this is split into two loop pass pipelines because we run
   // some function passes in between them. These can and should be replaced by
   // loop pass equivalenst but those aren't ready yet. Specifically,
-  // `SimplifyCFGPass` and `InstCombinePass` are used. We just have
-  // `LoopSimplifyCFGPass` which isn't yet powerful enough.
+  // `SimplifyCFGPass` and `InstCombinePass` are used. We have
+  // `LoopSimplifyCFGPass` which isn't yet powerful enough, and the closest to
+  // the other we have is `LoopInstSimplify`.
   LoopPassManager LPM1(DebugLogging), LPM2(DebugLogging);
 
   // Rotate Loop - disable header duplication at -Oz