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constant fold indirectbr(blockaddress(%bb)) -> br label %bb.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85704 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-11-01 03:40:38 +00:00
parent 43f44aa160
commit 0a4c6789d5
1 changed files with 46 additions and 9 deletions
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55
lib/Transforms/Utils/Local.cpp
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@ -110,7 +110,9 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
// unconditional branch. // unconditional branch.
BI->setUnconditionalDest(Destination); BI->setUnconditionalDest(Destination);
return true; return true;
} else if (Dest2 == Dest1) { // Conditional branch to same location? }
if (Dest2 == Dest1) { // Conditional branch to same location?
// This branch matches something like this: // This branch matches something like this:
// br bool %cond, label %Dest, label %Dest // br bool %cond, label %Dest, label %Dest
// and changes it into: br label %Dest // and changes it into: br label %Dest
@ -123,7 +125,10 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
BI->setUnconditionalDest(Dest1); BI->setUnconditionalDest(Dest1);
return true; return true;
} }
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(T)) { return false;
}
if (SwitchInst *SI = dyn_cast<SwitchInst>(T)) {
// If we are switching on a constant, we can convert the switch into a // If we are switching on a constant, we can convert the switch into a
// single branch instruction! // single branch instruction!
ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition()); ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition());
@ -132,7 +137,7 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
assert(TheOnlyDest == SI->getDefaultDest() && assert(TheOnlyDest == SI->getDefaultDest() &&
"Default destination is not successor #0?"); "Default destination is not successor #0?");
// Figure out which case it goes to... // Figure out which case it goes to.
for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) { for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
// Found case matching a constant operand? // Found case matching a constant operand?
if (SI->getSuccessorValue(i) == CI) { if (SI->getSuccessorValue(i) == CI) {
@ -143,7 +148,7 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
// Check to see if this branch is going to the same place as the default // Check to see if this branch is going to the same place as the default
// dest. If so, eliminate it as an explicit compare. // dest. If so, eliminate it as an explicit compare.
if (SI->getSuccessor(i) == DefaultDest) { if (SI->getSuccessor(i) == DefaultDest) {
// Remove this entry... // Remove this entry.
DefaultDest->removePredecessor(SI->getParent()); DefaultDest->removePredecessor(SI->getParent());
SI->removeCase(i); SI->removeCase(i);
--i; --e; // Don't skip an entry... --i; --e; // Don't skip an entry...
@ -165,7 +170,7 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
// If we found a single destination that we can fold the switch into, do so // If we found a single destination that we can fold the switch into, do so
// now. // now.
if (TheOnlyDest) { if (TheOnlyDest) {
// Insert the new branch.. // Insert the new branch.
BranchInst::Create(TheOnlyDest, SI); BranchInst::Create(TheOnlyDest, SI);
BasicBlock *BB = SI->getParent(); BasicBlock *BB = SI->getParent();
@ -179,22 +184,54 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
Succ->removePredecessor(BB); Succ->removePredecessor(BB);
} }
// Delete the old switch... // Delete the old switch.
BB->getInstList().erase(SI); BB->getInstList().erase(SI);
return true; return true;
} else if (SI->getNumSuccessors() == 2) { }
if (SI->getNumSuccessors() == 2) {
// Otherwise, we can fold this switch into a conditional branch // Otherwise, we can fold this switch into a conditional branch
// instruction if it has only one non-default destination. // instruction if it has only one non-default destination.
Value *Cond = new ICmpInst(SI, ICmpInst::ICMP_EQ, SI->getCondition(), Value *Cond = new ICmpInst(SI, ICmpInst::ICMP_EQ, SI->getCondition(),
SI->getSuccessorValue(1), "cond"); SI->getSuccessorValue(1), "cond");
// Insert the new branch... // Insert the new branch.
BranchInst::Create(SI->getSuccessor(1), SI->getSuccessor(0), Cond, SI); BranchInst::Create(SI->getSuccessor(1), SI->getSuccessor(0), Cond, SI);
// Delete the old switch... // Delete the old switch.
SI->eraseFromParent(); SI->eraseFromParent();
return true; return true;
} }
return false;
} }
if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(T)) {
// indirectbr blockaddress(@F, @BB) -> br label @BB
if (BlockAddress *BA =
dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) {
BasicBlock *TheOnlyDest = BA->getBasicBlock();
// Insert the new branch.
BranchInst::Create(TheOnlyDest, IBI);
for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
if (IBI->getDestination(i) == TheOnlyDest)
TheOnlyDest = 0;
else
IBI->getDestination(i)->removePredecessor(IBI->getParent());
}
IBI->eraseFromParent();
// If we didn't find our destination in the IBI successor list, then we
// have undefined behavior. Replace the unconditional branch with an
// 'unreachable' instruction.
if (TheOnlyDest) {
BB->getTerminator()->eraseFromParent();
new UnreachableInst(BB->getContext(), BB);
}
return true;
}
}
return false; return false;
} }