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Ignore unreachable blocks when doing memory dependence analysis on non-local

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loads. It's not really profitable and may result in GVN going into an infinite
loop when it hits constructs like this:

     %x = gep %some.type %x, ...

Found via an LTO build of LLVM.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166490 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2012-10-23 18:37:11 +00:00
parent 5a719fcb5e
commit b846719663
2 changed files with 38 additions and 2 deletions
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4
lib/Analysis/MemoryDependenceAnalysis.cpp
View File

@ -983,7 +983,7 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
I != E; ++I) {
Visited.insert(std::make_pair(I->getBB(), Addr));
if (!I->getResult().isNonLocal())
if (!I->getResult().isNonLocal() && DT->isReachableFromEntry(I->getBB()))
Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), Addr));
}
++NumCacheCompleteNonLocalPtr;
@ -1029,7 +1029,7 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
NumSortedEntries);
// If we got a Def or Clobber, add this to the list of results.
if (!Dep.isNonLocal()) {
if (!Dep.isNonLocal() && DT->isReachableFromEntry(BB)) {
Result.push_back(NonLocalDepResult(BB, Dep, Pointer.getAddr()));
continue;
}

36
test/Transforms/GVN/crash.ll
View File

@ -163,3 +163,39 @@ entry:
ret i8 %1
}
; Test that a GEP in an unreachable block with the following form doesn't crash
; GVN:
;
; %x = gep %some.type %x, ...
%struct.type = type { i64, i32, i32 }
define fastcc void @func() nounwind uwtable ssp align 2 {
entry:
br label %reachable.bb
;; Unreachable code.
unreachable.bb:
%gep.val = getelementptr inbounds %struct.type* %gep.val, i64 1
br i1 undef, label %u2.bb, label %u1.bb
u1.bb:
%tmp1 = getelementptr inbounds %struct.type* %gep.val, i64 0, i32 0
store i64 -1, i64* %tmp1, align 8
br label %unreachable.bb
u2.bb:
%0 = load i32* undef, align 4
%conv.i.i.i.i.i = zext i32 %0 to i64
br label %u2.bb
;; Reachable code.
reachable.bb:
br label %r1.bb
r1.bb:
br label %u2.bb
}