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Fix SCCP/2004-12-10-UndefBranchBug.ll

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18776 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-12-10 20:41:50 +00:00
parent bfaf88a4d3
commit fc6ac50619
1 changed files with 51 additions and 3 deletions
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54
lib/Transforms/Scalar/SCCP.cpp
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@ -153,6 +153,13 @@ public:
///
void Solve();
/// ResolveBranchesIn - While solving the dataflow for a function, we assume
/// that branches on undef values cannot reach any of their successors.
/// However, this is not a safe assumption. After we solve dataflow, this
/// method should be use to handle this. If this returns true, the solver
/// should be rerun.
bool ResolveBranchesIn(Function &F);
/// getExecutableBlocks - Once we have solved for constants, return the set of
/// blocks that is known to be executable.
std::set<BasicBlock*> &getExecutableBlocks() {
@ -869,6 +876,36 @@ void SCCPSolver::Solve() {
}
}
/// ResolveBranchesIn - While solving the dataflow for a function, we assume
/// that branches on undef values cannot reach any of their successors.
/// However, this is not a safe assumption. After we solve dataflow, this
/// method should be use to handle this. If this returns true, the solver
/// should be rerun.
bool SCCPSolver::ResolveBranchesIn(Function &F) {
bool BranchesResolved = false;
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
TerminatorInst *TI = BB->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isConditional()) {
LatticeVal &BCValue = getValueState(BI->getCondition());
if (BCValue.isUndefined()) {
BI->setCondition(ConstantBool::True);
BranchesResolved = true;
visit(BI);
}
}
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
LatticeVal &SCValue = getValueState(SI->getCondition());
if (SCValue.isUndefined()) {
SI->setCondition(Constant::getNullValue(SI->getCondition()->getType()));
BranchesResolved = true;
visit(SI);
}
}
}
return BranchesResolved;
}
namespace {
Statistic<> NumInstRemoved("sccp", "Number of instructions removed");
@ -916,7 +953,11 @@ bool SCCP::runOnFunction(Function &F) {
Values[AI].markOverdefined();
// Solve for constants.
Solver.Solve();
bool ResolvedBranches = true;
while (ResolvedBranches) {
Solver.Solve();
ResolvedBranches = Solver.ResolveBranchesIn(F);
}
bool MadeChanges = false;
@ -1037,7 +1078,14 @@ bool IPSCCP::runOnModule(Module &M) {
}
// Solve for constants.
Solver.Solve();
bool ResolvedBranches = true;
while (ResolvedBranches) {
Solver.Solve();
ResolvedBranches = false;
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
ResolvedBranches |= Solver.ResolveBranchesIn(*F);
}
bool MadeChanges = false;
@ -1065,7 +1113,7 @@ bool IPSCCP::runOnModule(Module &M) {
if (!ExecutableBBs.count(BB)) {
DEBUG(std::cerr << " BasicBlock Dead:" << *BB);
++IPNumDeadBlocks;
// Delete the instructions backwards, as it has a reduced likelihood of
// having to update as many def-use and use-def chains.
std::vector<Instruction*> Insts;