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Fix handling of forward unreachable but reverse-reachable blocks in MemorySSA construction

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llvm-svn: 274606
This commit is contained in:
Daniel Berlin 2016-07-06 05:32:05 +00:00
parent 849887c0a3
commit e473c8b506
2 changed files with 39 additions and 2 deletions
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18
lib/Transforms/Utils/MemorySSA.cpp
View File

@ -201,8 +201,6 @@ MemoryAccess *MemorySSA::renameBlock(BasicBlock *BB,
continue;
AccessList *Accesses = It->second.get();
auto *Phi = cast<MemoryPhi>(&Accesses->front());
assert(std::find(succ_begin(BB), succ_end(BB), S) != succ_end(BB) &&
"Must be at least one edge from Succ to BB!");
Phi->addIncoming(IncomingVal, BB);
}
@ -252,6 +250,22 @@ void MemorySSA::markUnreachableAsLiveOnEntry(BasicBlock *BB) {
assert(!DT->isReachableFromEntry(BB) &&
"Reachable block found while handling unreachable blocks");
// Make sure phi nodes in our reachable successors end up with a
// LiveOnEntryDef for our incoming edge, even though our block is forward
// unreachable. We could just disconnect these blocks from the CFG fully,
// but we do not right now.
for (const BasicBlock *S : successors(BB)) {
if (!DT->isReachableFromEntry(S))
continue;
auto It = PerBlockAccesses.find(S);
// Rename the phi nodes in our successor block
if (It == PerBlockAccesses.end() || !isa<MemoryPhi>(It->second->front()))
continue;
AccessList *Accesses = It->second.get();
auto *Phi = cast<MemoryPhi>(&Accesses->front());
Phi->addIncoming(LiveOnEntryDef.get(), BB);
}
auto It = PerBlockAccesses.find(BB);
if (It == PerBlockAccesses.end())
return;

23
test/Transforms/Util/MemorySSA/forward-unreachable.ll Normal file
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@ -0,0 +1,23 @@
; RUN: opt -aa-pipeline=basic-aa -passes='print<memoryssa>,verify<memoryssa>' -disable-output < %s 2>&1 | FileCheck %s
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
define void @test() {
entry:
br i1 undef, label %split1, label %split2
split1:
store i16 undef, i16* undef, align 2
br label %merge
split2:
br label %merge
forwardunreachable:
br label %merge
merge:
; The forwardunreachable block still needs an entry in the phi node,
; because it is reverse reachable, so the CFG still has it as a
; predecessor of the block
; CHECK: 3 = MemoryPhi({split1,1},{split2,liveOnEntry},{forwardunreachable,liveOnEntry})
store i16 undef, i16* undef, align 2
ret void
}