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Avoid building data structures we don't really need. This improves the runtime 

of a test that Bill Wendling sent me from 228.5s to 105s.  Obviously there is
more improvement to be had, but this is a nice speedup which should be "felt"
by many programs.

llvm-svn: 8962
This commit is contained in:
Chris Lattner 2003-10-08 15:47:41 +00:00
parent c4788bbde0
commit 71ac22ffb5
1 changed files with 39 additions and 10 deletions
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47
llvm/lib/Transforms/Scalar/SCCP.cpp
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@ -381,17 +381,46 @@ bool SCCP::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
if (!BBExecutable.count(From)) return false;
// Check to make sure this edge itself is actually feasible now...
TerminatorInst *FT = From->getTerminator();
std::vector<bool> SuccFeasible;
getFeasibleSuccessors(*FT, SuccFeasible);
// Check all edges from From to To. If any are feasible, return true.
for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i)
if (FT->getSuccessor(i) == To && SuccFeasible[i])
TerminatorInst *TI = From->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isUnconditional())
return true;
else {
InstVal &BCValue = getValueState(BI->getCondition());
if (BCValue.isOverdefined()) {
// Overdefined condition variables mean the branch could go either way.
return true;
} else if (BCValue.isConstant()) {
// Constant condition variables mean the branch can only go a single way
return BI->getSuccessor(BCValue.getConstant() ==
ConstantBool::False) == To;
}
return false;
}
} else if (InvokeInst *II = dyn_cast<InvokeInst>(TI)) {
// Invoke instructions successors are always executable.
return true;
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
InstVal &SCValue = getValueState(SI->getCondition());
if (SCValue.isOverdefined()) { // Overdefined condition?
// All destinations are executable!
return true;
} else if (SCValue.isConstant()) {
Constant *CPV = SCValue.getConstant();
// Make sure to skip the "default value" which isn't a value
for (unsigned i = 1, E = SI->getNumSuccessors(); i != E; ++i)
if (SI->getSuccessorValue(i) == CPV) // Found the taken branch...
return SI->getSuccessor(i) == To;
// Otherwise, none of the edges are actually feasible at this time...
return false;
// Constant value not equal to any of the branches... must execute
// default branch then...
return SI->getDefaultDest() == To;
}
return false;
} else {
std::cerr << "Unknown terminator instruction: " << *TI;
abort();
}
}
// visit Implementations - Something changed in this instruction... Either an