#include "llvm/Constants.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Pass.h"
#include "llvm/Type.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
void SimplifyPredecessors(BranchInst *BI);
void SimplifyPredecessors(SwitchInst *SI);
void RevectorBlockTo(BasicBlock *FromBB, BasicBlock *ToBB);
+ bool RevectorBlockTo(BasicBlock *FromBB, Value *Cond, BranchInst *BI);
};
}
// jump directly to the destination instead of going through this block.
void CondProp::SimplifyPredecessors(BranchInst *BI) {
// TODO: We currently only handle the most trival case, where the PHI node has
- // one use (the branch), and is the only instruction besides the branch in the
- // block.
+ // one use (the branch), and is the only instruction besides the branch and dbg
+ // intrinsics in the block.
PHINode *PN = cast<PHINode>(BI->getCondition());
if (PN->getNumIncomingValues() == 1) {
if (!PN->hasOneUse()) return;
BasicBlock *BB = BI->getParent();
- if (&*BB->begin() != PN || &*next(BB->begin()) != BI)
+ if (&*BB->begin() != PN)
+ return;
+ BasicBlock::iterator BBI = BB->begin();
+ BasicBlock::iterator BBE = BB->end();
+ while (BBI != BBE && isa<DbgInfoIntrinsic>(++BBI)) /* empty */;
+ if (&*BBI != BI)
return;
// Ok, we have this really simple case, walk the PHI operands, looking for
// constants. Walk from the end to remove operands from the end when
// possible, and to avoid invalidating "i".
- for (unsigned i = PN->getNumIncomingValues(); i != 0; --i)
- if (ConstantInt *CB = dyn_cast<ConstantInt>(PN->getIncomingValue(i-1))) {
- // If we have a constant, forward the edge from its current to its
- // ultimate destination.
- RevectorBlockTo(PN->getIncomingBlock(i-1),
- BI->getSuccessor(CB->isZero()));
- ++NumBrThread;
-
- // If there were two predecessors before this simplification, or if the
- // PHI node contained all the same value except for the one we just
- // substituted, the PHI node may be deleted. Don't iterate through it the
- // last time.
- if (BI->getCondition() != PN) return;
- }
+ for (unsigned i = PN->getNumIncomingValues(); i != 0; --i) {
+ Value *InVal = PN->getIncomingValue(i-1);
+ if (!RevectorBlockTo(PN->getIncomingBlock(i-1), InVal, BI))
+ continue;
+
+ ++NumBrThread;
+
+ // If there were two predecessors before this simplification, or if the
+ // PHI node contained all the same value except for the one we just
+ // substituted, the PHI node may be deleted. Don't iterate through it the
+ // last time.
+ if (BI->getCondition() != PN) return;
+ }
}
// SimplifyPredecessors(switch) - We know that SI is switch based on a PHI node
// the destination instead of going through this block.
void CondProp::SimplifyPredecessors(SwitchInst *SI) {
// TODO: We currently only handle the most trival case, where the PHI node has
- // one use (the branch), and is the only instruction besides the branch in the
- // block.
+ // one use (the branch), and is the only instruction besides the branch and
+ // dbg intrinsics in the block.
PHINode *PN = cast<PHINode>(SI->getCondition());
if (!PN->hasOneUse()) return;
BasicBlock *BB = SI->getParent();
- if (&*BB->begin() != PN || &*next(BB->begin()) != SI)
+ if (&*BB->begin() != PN)
+ return;
+ BasicBlock::iterator BBI = BB->begin();
+ BasicBlock::iterator BBE = BB->end();
+ while (BBI != BBE && isa<DbgInfoIntrinsic>(++BBI)) /* empty */;
+ if (&*BBI != SI)
return;
bool RemovedPreds = false;
MadeChange = true;
}
+
+bool CondProp::RevectorBlockTo(BasicBlock *FromBB, Value *Cond, BranchInst *BI){
+ BranchInst *FromBr = cast<BranchInst>(FromBB->getTerminator());
+ if (!FromBr->isUnconditional())
+ return false;
+
+ // Get the old block we are threading through.
+ BasicBlock *OldSucc = FromBr->getSuccessor(0);
+
+ // If the condition is a constant, simply revector the unconditional branch at
+ // the end of FromBB to one of the successors of its current successor.
+ if (ConstantInt *CB = dyn_cast<ConstantInt>(Cond)) {
+ BasicBlock *ToBB = BI->getSuccessor(CB->isZero());
+
+ // OldSucc had multiple successors. If ToBB has multiple predecessors, then
+ // the edge between them would be critical, which we already took care of.
+ // If ToBB has single operand PHI node then take care of it here.
+ FoldSingleEntryPHINodes(ToBB);
+
+ // Update PHI nodes in OldSucc to know that FromBB no longer branches to it.
+ OldSucc->removePredecessor(FromBB);
+
+ // Change FromBr to branch to the new destination.
+ FromBr->setSuccessor(0, ToBB);
+ } else {
+ BasicBlock *Succ0 = BI->getSuccessor(0);
+ // Do not perform transform if the new destination has PHI nodes. The
+ // transform will add new preds to the PHI's.
+ if (isa<PHINode>(Succ0->begin()))
+ return false;
+
+ BasicBlock *Succ1 = BI->getSuccessor(1);
+ if (isa<PHINode>(Succ1->begin()))
+ return false;
+
+ // Insert the new conditional branch.
+ BranchInst::Create(Succ0, Succ1, Cond, FromBr);
+
+ FoldSingleEntryPHINodes(Succ0);
+ FoldSingleEntryPHINodes(Succ1);
+
+ // Update PHI nodes in OldSucc to know that FromBB no longer branches to it.
+ OldSucc->removePredecessor(FromBB);
+
+ // Delete the old branch.
+ FromBr->eraseFromParent();
+ }
+
+ MadeChange = true;
+ return true;
+}
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