[llvm] r326177 - [MemorySSA] Invalidate def caches on deletion

[George Burgess IV via llvm-commits]

Author: gbiv
Date: Mon Feb 26 23:20:49 2018
New Revision: 326177

URL: http://llvm.org/viewvc/llvm-project?rev=326177&view=rev
Log:
[MemorySSA] Invalidate def caches on deletion

The only cases I can come up with where this invalidation needs to
happen is when there's a deletion somewhere. If we find more creative
test-cases, we can probably go with another approach mentioned on
PR36529.

Fixes PR36529.

Modified:
    llvm/trunk/include/llvm/Analysis/MemorySSA.h
    llvm/trunk/unittests/Analysis/MemorySSA.cpp

Modified: llvm/trunk/include/llvm/Analysis/MemorySSA.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/MemorySSA.h?rev=326177&r1=326176&r2=326177&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/MemorySSA.h (original)
+++ llvm/trunk/include/llvm/Analysis/MemorySSA.h Mon Feb 26 23:20:49 2018
@@ -381,7 +381,9 @@ public:
     OptimizedID = getDefiningAccess()->getID();
   }
 
-  MemoryAccess *getOptimized() const { return Optimized; }
+  MemoryAccess *getOptimized() const {
+    return cast_or_null<MemoryAccess>(Optimized);
+  }
 
   bool isOptimized() const {
     return getOptimized() && getDefiningAccess() &&
@@ -401,7 +403,7 @@ private:
 
   const unsigned ID;
   unsigned OptimizedID = INVALID_MEMORYACCESS_ID;
-  MemoryAccess *Optimized = nullptr;
+  WeakVH Optimized;
 };
 
 template <>

Modified: llvm/trunk/unittests/Analysis/MemorySSA.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Analysis/MemorySSA.cpp?rev=326177&r1=326176&r2=326177&view=diff
==============================================================================
--- llvm/trunk/unittests/Analysis/MemorySSA.cpp (original)
+++ llvm/trunk/unittests/Analysis/MemorySSA.cpp Mon Feb 26 23:20:49 2018
@@ -951,3 +951,51 @@ TEST_F(MemorySSATest, MoveToBeforeLiveOn
             MSSA.getLiveOnEntryDef())
       << "(DefA = " << DefA << ")";
 }
+
+TEST_F(MemorySSATest, RemovingDefInvalidatesCache) {
+  // Create:
+  //   %x = alloca i8
+  //   %y = alloca i8
+  //   ; 1 = MemoryDef(liveOnEntry)
+  //   store i8 0, i8* %x
+  //   ; 2 = MemoryDef(1)
+  //   store i8 0, i8* %y
+  //   ; 3 = MemoryDef(2)
+  //   store i8 0, i8* %x
+  //
+  // And be sure that MSSA's caching handles the removal of def `1`
+  // appropriately.
+  IRBuilder<> B(C);
+  F = Function::Create(
+      FunctionType::get(B.getVoidTy(), {B.getInt8PtrTy()}, false),
+      GlobalValue::ExternalLinkage, "F", &M);
+
+  BasicBlock *Entry = BasicBlock::Create(C, "if", F);
+  B.SetInsertPoint(Entry);
+
+  Value *X = B.CreateAlloca(B.getInt8Ty());
+  Value *Y = B.CreateAlloca(B.getInt8Ty());
+  StoreInst *StoreX1 = B.CreateStore(B.getInt8(0), X);
+  StoreInst *StoreY = B.CreateStore(B.getInt8(0), Y);
+  StoreInst *StoreX2 = B.CreateStore(B.getInt8(0), X);
+
+  setupAnalyses();
+
+  MemorySSA &MSSA = *Analyses->MSSA;
+
+  auto *DefX1 = cast<MemoryDef>(MSSA.getMemoryAccess(StoreX1));
+  auto *DefY = cast<MemoryDef>(MSSA.getMemoryAccess(StoreY));
+  auto *DefX2 = cast<MemoryDef>(MSSA.getMemoryAccess(StoreX2));
+
+  EXPECT_EQ(DefX2->getDefiningAccess(), DefY);
+  MemoryAccess *X2Clobber = MSSA.getWalker()->getClobberingMemoryAccess(DefX2);
+  ASSERT_EQ(DefX1, X2Clobber);
+
+  MemorySSAUpdater(&MSSA).removeMemoryAccess(DefX1);
+  StoreX1->eraseFromParent();
+
+  EXPECT_EQ(DefX2->getDefiningAccess(), DefY);
+  EXPECT_EQ(MSSA.getWalker()->getClobberingMemoryAccess(DefX2),
+            MSSA.getLiveOnEntryDef())
+      << "(DefX1 = " << DefX1 << ")";
+}