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Merge branch 'ADCE5'

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llvm-svn: 281947
This commit is contained in:
David Callahan 2016-09-19 23:17:58 +00:00
parent 5bc3b7d901
commit ac0cc8c0ba
1 changed files with 39 additions and 2 deletions
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41
lib/Transforms/Scalar/ADCE.cpp
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@ -58,6 +58,10 @@ struct BlockInfoType {
bool Live = false;
/// True when this block ends in an unconditional branch.
bool UnconditionalBranch = false;
/// True when this block is known to have live PHI nodes.
bool HasLivePhiNodes = false;
/// Control dependence sources need to be live for this block.
bool CFLive = false;
/// Quick access to the LiveInfo for the terminator,
/// holds the value &InstInfo[Terminator]
@ -109,6 +113,9 @@ class AggressiveDeadCodeElimination {
void markLiveInstructions();
/// Mark an instruction as live.
void markLive(Instruction *I);
/// Mark terminators of control predecessors of a PHI node live.
void markPhiLive(PHINode *PN);
/// Record the Debug Scopes which surround live debug information.
void collectLiveScopes(const DILocalScope &LS);
@ -269,15 +276,18 @@ void AggressiveDeadCodeElimination::markLiveInstructions() {
// where we need to mark the inputs as live.
while (!Worklist.empty()) {
Instruction *LiveInst = Worklist.pop_back_val();
DEBUG(dbgs() << "work live: "; LiveInst->dump(););
// Collect the live debug info scopes attached to this instruction.
if (const DILocation *DL = LiveInst->getDebugLoc())
collectLiveScopes(*DL);
DEBUG(dbgs() << "work live: "; LiveInst->dump(););
for (Use &OI : LiveInst->operands())
if (Instruction *Inst = dyn_cast<Instruction>(OI))
markLive(Inst);
if (auto *PN = dyn_cast<PHINode>(LiveInst))
markPhiLive(PN);
}
markLiveBranchesFromControlDependences();
@ -315,7 +325,10 @@ void AggressiveDeadCodeElimination::markLive(Instruction *I) {
DEBUG(dbgs() << "mark block live: " << BBInfo.BB->getName() << '\n');
BBInfo.Live = true;
NewLiveBlocks.insert(BBInfo.BB);
if (!BBInfo.CFLive) {
BBInfo.CFLive = true;
NewLiveBlocks.insert(BBInfo.BB);
}
// Mark unconditional branches at the end of live
// blocks as live since there is no work to do for them later
@ -348,6 +361,25 @@ void AggressiveDeadCodeElimination::collectLiveScopes(const DILocation &DL) {
collectLiveScopes(*IA);
}
void AggressiveDeadCodeElimination::markPhiLive(PHINode *PN) {
auto &Info = BlockInfo[PN->getParent()];
// Only need to check this once per block.
if (Info.HasLivePhiNodes)
return;
Info.HasLivePhiNodes = true;
// If a predecessor block is not live, mark it as control-flow live
// which will trigger marking live branches upon which
// that block is control dependent.
for (auto *PredBB : predecessors(Info.BB)) {
auto &Info = BlockInfo[PredBB];
if (!Info.CFLive) {
Info.CFLive = true;
NewLiveBlocks.insert(PredBB);
}
}
}
void AggressiveDeadCodeElimination::markLiveBranchesFromControlDependences() {
if (BlocksWithDeadTerminators.empty())
@ -382,6 +414,11 @@ void AggressiveDeadCodeElimination::markLiveBranchesFromControlDependences() {
}
}
//===----------------------------------------------------------------------===//
//
// Routines to update the CFG and SSA information before removing dead code.
//
//===----------------------------------------------------------------------===//
bool AggressiveDeadCodeElimination::removeDeadInstructions() {
// The inverse of the live set is the dead set. These are those instructions