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Fix PR8247: JumpThreading can cause a block to become unreachable while still having predecessor, if it is part of a self-loop.

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Because of this, we cannot use the Simplify* APIs, as they can assert-fail on unreachable code.  Since it's not easy to determine
if a given threading will cause a block to become unreachable, simply defer simplifying simplification to later InstCombine and/or
DCE passes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115082 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson
2010-09-29 20:34:41 +00:00
parent 18d52f2fb5
commit 36c4debc94
2 changed files with 31 additions and 4 deletions
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8
lib/Transforms/Scalar/JumpThreading.cpp
View File

@@ -613,7 +613,7 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
TerminatorInst *BBTerm = BB->getTerminator(); TerminatorInst *BBTerm = BB->getTerminator();
for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i) { for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i) {
if (i == BestSucc) continue; if (i == BestSucc) continue;
RemovePredecessorAndSimplify(BBTerm->getSuccessor(i), BB, TD); BBTerm->getSuccessor(i)->removePredecessor(BB, true);
} }
DEBUG(dbgs() << " In block '" << BB->getName() DEBUG(dbgs() << " In block '" << BB->getName()
@@ -664,7 +664,7 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
if (PI == PE) { if (PI == PE) {
unsigned ToRemove = Baseline == LazyValueInfo::True ? 1 : 0; unsigned ToRemove = Baseline == LazyValueInfo::True ? 1 : 0;
unsigned ToKeep = Baseline == LazyValueInfo::True ? 0 : 1; unsigned ToKeep = Baseline == LazyValueInfo::True ? 0 : 1;
RemovePredecessorAndSimplify(CondBr->getSuccessor(ToRemove), BB, TD); CondBr->getSuccessor(ToRemove)->removePredecessor(BB, true);
BranchInst::Create(CondBr->getSuccessor(ToKeep), CondBr); BranchInst::Create(CondBr->getSuccessor(ToKeep), CondBr);
CondBr->eraseFromParent(); CondBr->eraseFromParent();
return true; return true;
@@ -1470,7 +1470,7 @@ bool JumpThreading::ThreadEdge(BasicBlock *BB,
TerminatorInst *PredTerm = PredBB->getTerminator(); TerminatorInst *PredTerm = PredBB->getTerminator();
for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i) for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i)
if (PredTerm->getSuccessor(i) == BB) { if (PredTerm->getSuccessor(i) == BB) {
RemovePredecessorAndSimplify(BB, PredBB, TD); BB->removePredecessor(PredBB, true);
PredTerm->setSuccessor(i, NewBB); PredTerm->setSuccessor(i, NewBB);
} }
@@ -1620,7 +1620,7 @@ bool JumpThreading::DuplicateCondBranchOnPHIIntoPred(BasicBlock *BB,
// PredBB no longer jumps to BB, remove entries in the PHI node for the edge // PredBB no longer jumps to BB, remove entries in the PHI node for the edge
// that we nuked. // that we nuked.
RemovePredecessorAndSimplify(BB, PredBB, TD); BB->removePredecessor(PredBB, true);
// Remove the unconditional branch at the end of the PredBB block. // Remove the unconditional branch at the end of the PredBB block.
OldPredBranch->eraseFromParent(); OldPredBranch->eraseFromParent();

27
test/Transforms/JumpThreading/crash.ll
View File

@@ -484,3 +484,30 @@ bb269.us.us:
bb288.bb289.loopexit_crit_edge: bb288.bb289.loopexit_crit_edge:
unreachable unreachable
} }
; PR 8247
%struct.S1 = type { i8, i8 }
@func_89.l_245 = internal constant %struct.S1 { i8 33, i8 6 }, align 1
define void @func_89(i16 zeroext %p_90, %struct.S1* nocapture %p_91, i32* nocapture %p_92) nounwind ssp {
entry:
store i32 0, i32* %p_92, align 4
br i1 false, label %lbl_260, label %if.else
if.else: ; preds = %entry
br label %for.cond
for.cond: ; preds = %lbl_260, %if.else
%l_245.0 = phi i16 [ %l_245.1, %lbl_260 ], [ 33, %if.else ]
%l_261.0 = phi i32 [ %and, %lbl_260 ], [ 255, %if.else ]
%tobool21 = icmp ult i16 %l_245.0, 256
br i1 %tobool21, label %if.end, label %lbl_260
lbl_260: ; preds = %for.cond, %entry
%l_245.1 = phi i16 [ 1569, %entry ], [ %l_245.0, %for.cond ]
%l_261.1 = phi i32 [ 255, %entry ], [ %l_261.0, %for.cond ]
%and = and i32 %l_261.1, 1
br label %for.cond
if.end: ; preds = %for.cond
ret void
}