[llvm] r342209 - [LoopInterchange] Preserve ScalarEvolution, by forgetting about interchanged loops.

[Florian Hahn via llvm-commits]

Author: fhahn
Date: Fri Sep 14 00:50:20 2018
New Revision: 342209

URL: http://llvm.org/viewvc/llvm-project?rev=342209&view=rev
Log:
[LoopInterchange] Preserve ScalarEvolution, by forgetting about interchanged loops.

As preparation for LoopInterchange becoming a loop pass, it needs to
preserve ScalarEvolution. Even though interchanging should not change
the trip count of the loop, it modifies loop entry, latch and exit
blocks.

I added -verify-scev to some loop interchange tests, but the verification does
not catch problems caused by missing invalidation of SE in loop interchange, as
the trip counts themselves do not change. So there might be potential to
make the SE verification covering more stuff in the future.

Reviewers: mkazantsev, efriedma, karthikthecool

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D52026


Modified:
    llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp
    llvm/trunk/test/Transforms/LoopInterchange/interchangeable.ll
    llvm/trunk/test/Transforms/LoopInterchange/phi-ordering.ll

Modified: llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp?rev=342209&r1=342208&r2=342209&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp Fri Sep 14 00:50:20 2018
@@ -454,6 +454,7 @@ struct LoopInterchange : public Function
 
     AU.addPreserved<DominatorTreeWrapperPass>();
     AU.addPreserved<LoopInfoWrapperPass>();
+    AU.addPreserved<ScalarEvolutionWrapperPass>();
   }
 
   bool runOnFunction(Function &F) override {
@@ -1231,6 +1232,10 @@ void LoopInterchangeTransform::restructu
   // outer loop.
   NewOuter->addBlockEntry(OrigOuterPreHeader);
   LI->changeLoopFor(OrigOuterPreHeader, NewOuter);
+
+  // Tell SE that we move the loops around.
+  SE->forgetLoop(NewOuter);
+  SE->forgetLoop(NewInner);
 }
 
 bool LoopInterchangeTransform::transform() {

Modified: llvm/trunk/test/Transforms/LoopInterchange/interchangeable.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopInterchange/interchangeable.ll?rev=342209&r1=342208&r2=342209&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopInterchange/interchangeable.ll (original)
+++ llvm/trunk/test/Transforms/LoopInterchange/interchangeable.ll Fri Sep 14 00:50:20 2018
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -basicaa -loop-interchange -verify-dom-info -verify-loop-info -S | FileCheck %s
+; RUN: opt < %s -basicaa -loop-interchange -verify-dom-info -verify-loop-info -verify-scev -S | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"

Modified: llvm/trunk/test/Transforms/LoopInterchange/phi-ordering.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopInterchange/phi-ordering.ll?rev=342209&r1=342208&r2=342209&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopInterchange/phi-ordering.ll (original)
+++ llvm/trunk/test/Transforms/LoopInterchange/phi-ordering.ll Fri Sep 14 00:50:20 2018
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -loop-interchange -verify-dom-info -verify-loop-info -S 2>&1 | FileCheck %s
+; RUN: opt < %s -loop-interchange -verify-dom-info -verify-loop-info -verify-scev -S 2>&1 | FileCheck %s
 ;; Checks the order of the inner phi nodes does not cause havoc.
 ;; The inner loop has a reduction into c. The IV is not the first phi.