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Another attempt at making ArgPromotion smarter. This patch no longer breaks Burg.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30657 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2006-09-28 23:02:22 +00:00
parent 40d31ecb29
commit 3295471846
1 changed files with 49 additions and 1 deletions
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50
lib/Transforms/IPO/ArgumentPromotion.cpp
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@ -179,6 +179,53 @@ static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) {
return true;
}
/// AccessOccursOnPath - Returns true if and only if a load or GEP instruction
/// on Pointer occurs in Path, or in every control-flow path that succeeds it.
bool AccessOccursOnPath(Value* V, BasicBlock* Start) {
std::vector<BasicBlock*> Worklist;
Worklist.push_back(Start);
std::set<BasicBlock*> Visited;
while (!Worklist.empty()) {
BasicBlock* BB = Worklist.back();
Worklist.pop_back();
Visited.insert(BB);
bool ContainsAccess = false;
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
if (isa<LoadInst>(I)) {
for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end(); OI != OE; ++OI)
if (*OI == V) {
ContainsAccess = true;
break;
}
} else if (isa<GetElementPtrInst>(I)) {
for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end(); OI != OE; ++OI)
if (*OI == V) {
ContainsAccess = AccessOccursOnPath(I, I->getParent());
break;
}
}
if (ContainsAccess)
break;
}
if (ContainsAccess) continue;
TerminatorInst* TI = BB->getTerminator();
if (isa<BranchInst>(TI) || isa<SwitchInst>(TI)) {
for (unsigned i = 0; i < TI->getNumSuccessors(); ++i)
if (!Visited.count(TI->getSuccessor(i)))
Worklist.push_back(TI->getSuccessor(i));
} else {
return false;
}
}
return true;
}
/// isSafeToPromoteArgument - As you might guess from the name of this method,
/// it checks to see if it is both safe and useful to promote the argument.
@ -252,7 +299,8 @@ bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg) const {
// of the pointer in the entry block of the function) or if we can prove that
// all pointers passed in are always to legal locations (for example, no null
// pointers are passed in, no pointers to free'd memory, etc).
if (!HasLoadInEntryBlock && !AllCalleesPassInValidPointerForArgument(Arg))
if (!AccessOccursOnPath(Arg, Arg->getParent()->begin()) &&
!AllCalleesPassInValidPointerForArgument(Arg))
return false; // Cannot prove that this is safe!!
// Okay, now we know that the argument is only used by load instructions and