commit 58a37754bb107ee1bd2e7a94f1da39fcebe900d9
author Alina Sbirlea <asbirlea@google.com> Wed Jul 10 17:36:56 2019 +0000
committer Alina Sbirlea <asbirlea@google.com> Wed Jul 10 17:36:56 2019 +0000
tree 69f7c671b3ca062c45d6ec1c70f7c1e6bb16c447
parent 843f198a83d8161dc580562cbe11643ed2b0e54f

[LoopRotate + MemorySSA] Keep an <instruction-cloned instruction> map.

Summary:
The map kept in loop rotate is used for instruction remapping, in order
to simplify the clones of instructions. Thus, if an instruction can be
simplified, its simplified value is placed in the map, even when the
clone is added to the IR. MemorySSA in contrast needs to know about that
clone, so it can add an access for it.
To resolve this: keep a different map for MemorySSA.

Reviewers: george.burgess.iv

Subscribers: jlebar, Prazek, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63680

llvm-svn: 365672

llvm/lib/Transforms/Utils/LoopRotationUtils.cpp

diff --git a/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp b/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
index 88c4937..37389a6 100644
--- a/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
@@ -295,7 +295,7 @@
   // Begin by walking OrigHeader and populating ValueMap with an entry for
   // each Instruction.
   BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end();
-  ValueToValueMapTy ValueMap;
+  ValueToValueMapTy ValueMap, ValueMapMSSA;
 
   // For PHI nodes, the value available in OldPreHeader is just the
   // incoming value from OldPreHeader.
@@ -374,6 +374,9 @@
       if (auto *II = dyn_cast<IntrinsicInst>(C))
         if (II->getIntrinsicID() == Intrinsic::assume)
           AC->registerAssumption(II);
+      // MemorySSA cares whether the cloned instruction was inserted or not, and
+      // not whether it can be remapped to a simplified value.
+      ValueMapMSSA[Inst] = C;
     }
   }
 
@@ -391,10 +394,11 @@
   LoopEntryBranch->eraseFromParent();
 
   // Update MemorySSA before the rewrite call below changes the 1:1
-  // instruction:cloned_instruction_or_value mapping in ValueMap.
+  // instruction:cloned_instruction_or_value mapping.
   if (MSSAU) {
-    ValueMap[OrigHeader] = OrigPreheader;
-    MSSAU->updateForClonedBlockIntoPred(OrigHeader, OrigPreheader, ValueMap);
+    ValueMapMSSA[OrigHeader] = OrigPreheader;
+    MSSAU->updateForClonedBlockIntoPred(OrigHeader, OrigPreheader,
+                                        ValueMapMSSA);
   }
 
   SmallVector<PHINode*, 2> InsertedPHIs;