[llvm] 63844c1 - [MemorySSA] Clean up single value phis.

[Alina Sbirlea via llvm-commits]

Author: Alina Sbirlea
Date: 2020-08-31T19:26:08-07:00
New Revision: 63844c116a0acf8a75ebe4ed6f25fced3c655710

URL: https://github.com/llvm/llvm-project/commit/63844c116a0acf8a75ebe4ed6f25fced3c655710
DIFF: https://github.com/llvm/llvm-project/commit/63844c116a0acf8a75ebe4ed6f25fced3c655710.diff

LOG: [MemorySSA] Clean up single value phis.

MemoryPhis with a single value are correct, but can lead to errors when
updating. Clean up single entry Phis newly added when cloning blocks.
Resolves PR46574.

Added: 
    llvm/test/Analysis/MemorySSA/pr46574.ll

Modified: 
    llvm/lib/Analysis/MemorySSAUpdater.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/MemorySSAUpdater.cpp b/llvm/lib/Analysis/MemorySSAUpdater.cpp
index 1de562fd7f31..671d9e60ab7a 100644
--- a/llvm/lib/Analysis/MemorySSAUpdater.cpp
+++ b/llvm/lib/Analysis/MemorySSAUpdater.cpp
@@ -543,6 +543,20 @@ void MemorySSAUpdater::removeDuplicatePhiEdgesBetween(const BasicBlock *From,
   }
 }
 
+/// If all arguments of a MemoryPHI are defined by the same incoming
+/// argument, return that argument.
+static MemoryAccess *onlySingleValue(MemoryPhi *MP) {
+  MemoryAccess *MA = nullptr;
+
+  for (auto &Arg : MP->operands()) {
+    if (!MA)
+      MA = cast<MemoryAccess>(Arg);
+    else if (MA != Arg)
+      return nullptr;
+  }
+  return MA;
+}
+
 static MemoryAccess *getNewDefiningAccessForClone(MemoryAccess *MA,
                                                   const ValueToValueMapTy &VMap,
                                                   PhiToDefMap &MPhiMap,
@@ -699,6 +713,10 @@ void MemorySSAUpdater::updateForClonedLoop(const LoopBlocksRPO &LoopBlocks,
           NewPhi->addIncoming(IncPhi, IncBB);
       }
     }
+    if (onlySingleValue(NewPhi)) {
+      MPhiMap[Phi] = nullptr;
+      removeMemoryAccess(NewPhi);
+    }
   };
 
   auto ProcessBlock = [&](BasicBlock *BB) {
@@ -1231,20 +1249,6 @@ void MemorySSAUpdater::moveAllAfterMergeBlocks(BasicBlock *From, BasicBlock *To,
       MPhi->setIncomingBlock(MPhi->getBasicBlockIndex(From), To);
 }
 
-/// If all arguments of a MemoryPHI are defined by the same incoming
-/// argument, return that argument.
-static MemoryAccess *onlySingleValue(MemoryPhi *MP) {
-  MemoryAccess *MA = nullptr;
-
-  for (auto &Arg : MP->operands()) {
-    if (!MA)
-      MA = cast<MemoryAccess>(Arg);
-    else if (MA != Arg)
-      return nullptr;
-  }
-  return MA;
-}
-
 void MemorySSAUpdater::wireOldPredecessorsToNewImmediatePredecessor(
     BasicBlock *Old, BasicBlock *New, ArrayRef<BasicBlock *> Preds,
     bool IdenticalEdgesWereMerged) {

diff  --git a/llvm/test/Analysis/MemorySSA/pr46574.ll b/llvm/test/Analysis/MemorySSA/pr46574.ll
new file mode 100644
index 000000000000..4e107478ab50
--- /dev/null
+++ b/llvm/test/Analysis/MemorySSA/pr46574.ll
@@ -0,0 +1,33 @@
+; RUN: opt -loop-instsimplify -loop-simplifycfg -licm -simple-loop-unswitch -enable-nontrivial-unswitch %s -disable-output
+; REQUIRES: asserts
+
+%0 = type { i24, i32, i32, i8 }
+
+ at g_1077 = external dso_local local_unnamed_addr global [4 x [3 x [2 x { i8, i8, i8, i8, i8, i8, i8, i8, i32 }]]], align 4
+
+define void @func_22() {
+bb:
+  br label %bb13
+
+bb13:                                             ; preds = %bb38, %bb31, %bb
+  %i15 = load i32, i32* undef, align 4
+  %i16 = trunc i32 %i15 to i8
+  %i18 = load %0*, %0** undef, align 8
+  %i19 = icmp eq %0* %i18, null
+  br i1 %i19, label %bb31, label %safe_mod_func_uint8_t_u_u.exit
+
+bb31:                                             ; preds = %bb13
+  %i25 = load i8, i8* getelementptr inbounds ([4 x [3 x [2 x { i8, i8, i8, i8, i8, i8, i8, i8, i32 }]]], [4 x [3 x [2 x { i8, i8, i8, i8, i8, i8, i8, i8, i32 }]]]* @g_1077, i64 0, i64 2, i64 2, i64 1, i32 6), align 2
+  %i28 = or i8 %i25, %i16
+  store i8 %i28, i8* getelementptr inbounds ([4 x [3 x [2 x { i8, i8, i8, i8, i8, i8, i8, i8, i32 }]]], [4 x [3 x [2 x { i8, i8, i8, i8, i8, i8, i8, i8, i32 }]]]* @g_1077, i64 0, i64 2, i64 2, i64 1, i32 6), align 2
+  %i30 = icmp ne i8 %i28, 0
+  %i37.not = icmp eq i8 %i16, 0
+  %or.cond = or i1 %i37.not, %i30
+  br i1 %or.cond, label %bb13, label %bb38
+
+safe_mod_func_uint8_t_u_u.exit:                   ; preds = %bb13
+  br label %bb38
+
+bb38:                                             ; preds = %safe_mod_func_uint8_t_u_u.exit, %bb31
+  br label %bb13
+}