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[MemorySSA] Fix a cache invalidation bug with removed accesses

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I suspect there's a deeper issue here, but we probably shouldn't be
using INVALID_MEMORYSSA_ID as liveOnEntry's ID anyway.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@325971 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
George Burgess IV 2018-02-23 23:07:18 +00:00
parent 5e4b515c4b
commit 3d238821f1
3 changed files with 45 additions and 3 deletions
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4
include/llvm/Analysis/MemorySSA.h
View File

@ -118,10 +118,10 @@ struct DefsOnlyTag {};
} // end namespace MSSAHelpers
enum {
enum : unsigned {
// Used to signify what the default invalid ID is for MemoryAccess's
// getID()
INVALID_MEMORYACCESS_ID = 0
INVALID_MEMORYACCESS_ID = -1U
};
template <class T> class memoryaccess_def_iterator_base;

2
lib/Analysis/MemorySSA.cpp
View File

@ -1033,7 +1033,7 @@ void MemorySSA::markUnreachableAsLiveOnEntry(BasicBlock *BB) {
MemorySSA::MemorySSA(Function &Func, AliasAnalysis *AA, DominatorTree *DT)
: AA(AA), DT(DT), F(Func), LiveOnEntryDef(nullptr), Walker(nullptr),
NextID(INVALID_MEMORYACCESS_ID) {
NextID(0) {
buildMemorySSA();
}

42
unittests/Analysis/MemorySSA.cpp
View File

@ -909,3 +909,45 @@ TEST_F(MemorySSATest, Irreducible) {
Updater.insertUse(LoadAccess);
MSSA.verifyMemorySSA();
}
TEST_F(MemorySSATest, MoveToBeforeLiveOnEntryInvalidatesCache) {
// Create:
// %1 = alloca i8
// ; 1 = MemoryDef(liveOnEntry)
// store i8 0, i8* %1
// ; 2 = MemoryDef(1)
// store i8 0, i8* %1
//
// ...And be sure that MSSA's caching doesn't give us `1` for the clobber of
// `2` after `1` is removed.
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 *A = B.CreateAlloca(B.getInt8Ty());
StoreInst *StoreA = B.CreateStore(B.getInt8(0), A);
StoreInst *StoreB = B.CreateStore(B.getInt8(0), A);
setupAnalyses();
MemorySSA &MSSA = *Analyses->MSSA;
auto *DefA = cast<MemoryDef>(MSSA.getMemoryAccess(StoreA));
auto *DefB = cast<MemoryDef>(MSSA.getMemoryAccess(StoreB));
MemoryAccess *BClobber = MSSA.getWalker()->getClobberingMemoryAccess(DefB);
ASSERT_EQ(DefA, BClobber);
MemorySSAUpdater(&MSSA).removeMemoryAccess(DefA);
StoreA->eraseFromParent();
EXPECT_EQ(DefB->getDefiningAccess(), MSSA.getLiveOnEntryDef());
EXPECT_EQ(MSSA.getWalker()->getClobberingMemoryAccess(DefB),
MSSA.getLiveOnEntryDef())
<< "(DefA = " << DefA << ")";
}