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Two bug fixes:

Browse Source 
1. Actually increment the Statistic for the GV elim optzn
 2. When resolving undef branches, only resolve branches in executable blocks,
    avoiding marking a bunch of completely dead blocks live.  This has a big
    impact on the quality of the generated code.

With this patch, we positively rip up vortex, compiling Ut_MoveBytes to a
single memcpy call. In vortex we get this:

     12 ipsccp           - Number of globals found to be constant
    986 ipsccp           - Number of arguments constant propagated
   1378 ipsccp           - Number of basic blocks unreachable
   8919 ipsccp           - Number of instructions removed


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18796 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-12-11 06:05:53 +00:00
parent 864737bf9e
commit dade2d22ba
1 changed files with 27 additions and 17 deletions

44
lib/Transforms/Scalar/SCCP.cpp

@ -217,7 +217,11 @@ private:
inline void markOverdefined(LatticeVal &IV, Value *V) {
if (IV.markOverdefined()) {
DEBUG(std::cerr << "markOverdefined: " << *V);
DEBUG(std::cerr << "markOverdefined: ";
if (Function *F = dyn_cast<Function>(V))
std::cerr << "Function '" << F->getName() << "'\n";
else
std::cerr << *V);
// Only instructions go on the work list
OverdefinedInstWorkList.push_back(V);
}
@ -934,26 +938,29 @@ void SCCPSolver::Solve() {
/// 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);
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
if (BBExecutable.count(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()) {
const Type *CondTy = SI->getCondition()->getType();
SI->setCondition(Constant::getNullValue(CondTy));
BranchesResolved = true;
visit(BI);
visit(SI);
}
}
} 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;
}
@ -1007,6 +1014,7 @@ bool SCCP::runOnFunction(Function &F) {
bool ResolvedBranches = true;
while (ResolvedBranches) {
Solver.Solve();
DEBUG(std::cerr << "RESOLVING UNDEF BRANCHES\n");
ResolvedBranches = Solver.ResolveBranchesIn(F);
}
@ -1146,6 +1154,7 @@ bool IPSCCP::runOnModule(Module &M) {
while (ResolvedBranches) {
Solver.Solve();
DEBUG(std::cerr << "RESOLVING UNDEF BRANCHES\n");
ResolvedBranches = false;
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
ResolvedBranches |= Solver.ResolveBranchesIn(*F);
@ -1284,6 +1293,7 @@ bool IPSCCP::runOnModule(Module &M) {
SI->eraseFromParent();
}
M.getGlobalList().erase(GV);
++IPNumGlobalConst;
}
return MadeChanges;