[PATCH] D52026: [LoopInterchange] Preserve ScalarEvolution, by forgetting about interchanged loops.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: mkazantsev, efriedma, karthikthecool.
Herald added a subscriber: javed.absar.

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.


https://reviews.llvm.org/D52026

Files:
  lib/Transforms/Scalar/LoopInterchange.cpp
  test/Transforms/LoopInterchange/interchangeable.ll
  test/Transforms/LoopInterchange/phi-ordering.ll


Index: test/Transforms/LoopInterchange/phi-ordering.ll
===================================================================
--- test/Transforms/LoopInterchange/phi-ordering.ll
+++ test/Transforms/LoopInterchange/phi-ordering.ll
@@ -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.
 
Index: test/Transforms/LoopInterchange/interchangeable.ll
===================================================================
--- test/Transforms/LoopInterchange/interchangeable.ll
+++ test/Transforms/LoopInterchange/interchangeable.ll
@@ -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"
Index: lib/Transforms/Scalar/LoopInterchange.cpp
===================================================================
--- lib/Transforms/Scalar/LoopInterchange.cpp
+++ lib/Transforms/Scalar/LoopInterchange.cpp
@@ -454,6 +454,7 @@
 
     AU.addPreserved<DominatorTreeWrapperPass>();
     AU.addPreserved<LoopInfoWrapperPass>();
+    AU.addPreserved<ScalarEvolutionWrapperPass>();
   }
 
   bool runOnFunction(Function &F) override {
@@ -1231,6 +1232,10 @@
   // 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() {


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D52026.165257.patch
Type: text/x-patch
Size: 2026 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20180913/7af0a1e1/attachment.bin>