mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-10-20 09:24:58 +00:00
pull a bunch of logic out of SimplifyCFG into a helper fn
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23407 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
parent
7c439929bc
commit
f58c1a578e
@ -1018,6 +1018,116 @@ static bool FoldCondBranchOnPHI(BranchInst *BI) {
|
||||
return false;
|
||||
}
|
||||
|
||||
/// FoldTwoEntryPHINode - Given a BB that starts with the specified two-entry
|
||||
/// PHI node, see if we can eliminate it.
|
||||
static bool FoldTwoEntryPHINode(PHINode *PN) {
|
||||
// Ok, this is a two entry PHI node. Check to see if this is a simple "if
|
||||
// statement", which has a very simple dominance structure. Basically, we
|
||||
// are trying to find the condition that is being branched on, which
|
||||
// subsequently causes this merge to happen. We really want control
|
||||
// dependence information for this check, but simplifycfg can't keep it up
|
||||
// to date, and this catches most of the cases we care about anyway.
|
||||
//
|
||||
BasicBlock *BB = PN->getParent();
|
||||
BasicBlock *IfTrue, *IfFalse;
|
||||
Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse);
|
||||
if (!IfCond) return false;
|
||||
|
||||
DEBUG(std::cerr << "FOUND IF CONDITION! " << *IfCond << " T: "
|
||||
<< IfTrue->getName() << " F: " << IfFalse->getName() << "\n");
|
||||
|
||||
// Loop over the PHI's seeing if we can promote them all to select
|
||||
// instructions. While we are at it, keep track of the instructions
|
||||
// that need to be moved to the dominating block.
|
||||
std::set<Instruction*> AggressiveInsts;
|
||||
|
||||
bool CanPromote = true;
|
||||
BasicBlock::iterator AfterPHIIt = BB->begin();
|
||||
while (isa<PHINode>(AfterPHIIt)) {
|
||||
PHINode *PN = cast<PHINode>(AfterPHIIt++);
|
||||
if (PN->getIncomingValue(0) == PN->getIncomingValue(1)) {
|
||||
if (PN->getIncomingValue(0) != PN)
|
||||
PN->replaceAllUsesWith(PN->getIncomingValue(0));
|
||||
else
|
||||
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
|
||||
} else if (!DominatesMergePoint(PN->getIncomingValue(0), BB,
|
||||
&AggressiveInsts) ||
|
||||
!DominatesMergePoint(PN->getIncomingValue(1), BB,
|
||||
&AggressiveInsts)) {
|
||||
CanPromote = false;
|
||||
}
|
||||
}
|
||||
|
||||
// Did we eliminate all PHI's?
|
||||
if (!CanPromote && AfterPHIIt != BB->begin())
|
||||
return false;
|
||||
|
||||
// If we all PHI nodes are promotable, check to make sure that all
|
||||
// instructions in the predecessor blocks can be promoted as well. If
|
||||
// not, we won't be able to get rid of the control flow, so it's not
|
||||
// worth promoting to select instructions.
|
||||
BasicBlock *DomBlock = 0, *IfBlock1 = 0, *IfBlock2 = 0;
|
||||
PN = cast<PHINode>(BB->begin());
|
||||
BasicBlock *Pred = PN->getIncomingBlock(0);
|
||||
if (cast<BranchInst>(Pred->getTerminator())->isUnconditional()) {
|
||||
IfBlock1 = Pred;
|
||||
DomBlock = *pred_begin(Pred);
|
||||
for (BasicBlock::iterator I = Pred->begin();
|
||||
!isa<TerminatorInst>(I); ++I)
|
||||
if (!AggressiveInsts.count(I)) {
|
||||
// This is not an aggressive instruction that we can promote.
|
||||
// Because of this, we won't be able to get rid of the control
|
||||
// flow, so the xform is not worth it.
|
||||
return false;
|
||||
}
|
||||
}
|
||||
|
||||
Pred = PN->getIncomingBlock(1);
|
||||
if (cast<BranchInst>(Pred->getTerminator())->isUnconditional()) {
|
||||
IfBlock2 = Pred;
|
||||
DomBlock = *pred_begin(Pred);
|
||||
for (BasicBlock::iterator I = Pred->begin();
|
||||
!isa<TerminatorInst>(I); ++I)
|
||||
if (!AggressiveInsts.count(I)) {
|
||||
// This is not an aggressive instruction that we can promote.
|
||||
// Because of this, we won't be able to get rid of the control
|
||||
// flow, so the xform is not worth it.
|
||||
return false;
|
||||
}
|
||||
}
|
||||
|
||||
// If we can still promote the PHI nodes after this gauntlet of tests,
|
||||
// do all of the PHI's now.
|
||||
|
||||
// Move all 'aggressive' instructions, which are defined in the
|
||||
// conditional parts of the if's up to the dominating block.
|
||||
if (IfBlock1) {
|
||||
DomBlock->getInstList().splice(DomBlock->getTerminator(),
|
||||
IfBlock1->getInstList(),
|
||||
IfBlock1->begin(),
|
||||
IfBlock1->getTerminator());
|
||||
}
|
||||
if (IfBlock2) {
|
||||
DomBlock->getInstList().splice(DomBlock->getTerminator(),
|
||||
IfBlock2->getInstList(),
|
||||
IfBlock2->begin(),
|
||||
IfBlock2->getTerminator());
|
||||
}
|
||||
|
||||
while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
|
||||
// Change the PHI node into a select instruction.
|
||||
Value *TrueVal =
|
||||
PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse);
|
||||
Value *FalseVal =
|
||||
PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue);
|
||||
|
||||
std::string Name = PN->getName(); PN->setName("");
|
||||
PN->replaceAllUsesWith(new SelectInst(IfCond, TrueVal, FalseVal,
|
||||
Name, AfterPHIIt));
|
||||
BB->getInstList().erase(PN);
|
||||
}
|
||||
return true;
|
||||
}
|
||||
|
||||
namespace {
|
||||
/// ConstantIntOrdering - This class implements a stable ordering of constant
|
||||
@ -1620,118 +1730,8 @@ bool llvm::SimplifyCFG(BasicBlock *BB) {
|
||||
// If there is a trivial two-entry PHI node in this basic block, and we can
|
||||
// eliminate it, do so now.
|
||||
if (PHINode *PN = dyn_cast<PHINode>(BB->begin()))
|
||||
if (PN->getNumIncomingValues() == 2) {
|
||||
// Ok, this is a two entry PHI node. Check to see if this is a simple "if
|
||||
// statement", which has a very simple dominance structure. Basically, we
|
||||
// are trying to find the condition that is being branched on, which
|
||||
// subsequently causes this merge to happen. We really want control
|
||||
// dependence information for this check, but simplifycfg can't keep it up
|
||||
// to date, and this catches most of the cases we care about anyway.
|
||||
//
|
||||
BasicBlock *IfTrue, *IfFalse;
|
||||
if (Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse)) {
|
||||
DEBUG(std::cerr << "FOUND IF CONDITION! " << *IfCond << " T: "
|
||||
<< IfTrue->getName() << " F: " << IfFalse->getName() << "\n");
|
||||
|
||||
// Loop over the PHI's seeing if we can promote them all to select
|
||||
// instructions. While we are at it, keep track of the instructions
|
||||
// that need to be moved to the dominating block.
|
||||
std::set<Instruction*> AggressiveInsts;
|
||||
bool CanPromote = true;
|
||||
|
||||
BasicBlock::iterator AfterPHIIt = BB->begin();
|
||||
while (isa<PHINode>(AfterPHIIt)) {
|
||||
PHINode *PN = cast<PHINode>(AfterPHIIt++);
|
||||
if (PN->getIncomingValue(0) == PN->getIncomingValue(1)) {
|
||||
if (PN->getIncomingValue(0) != PN)
|
||||
PN->replaceAllUsesWith(PN->getIncomingValue(0));
|
||||
else
|
||||
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
|
||||
} else if (!DominatesMergePoint(PN->getIncomingValue(0), BB,
|
||||
&AggressiveInsts) ||
|
||||
!DominatesMergePoint(PN->getIncomingValue(1), BB,
|
||||
&AggressiveInsts)) {
|
||||
CanPromote = false;
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
// Did we eliminate all PHI's?
|
||||
CanPromote |= AfterPHIIt == BB->begin();
|
||||
|
||||
// If we all PHI nodes are promotable, check to make sure that all
|
||||
// instructions in the predecessor blocks can be promoted as well. If
|
||||
// not, we won't be able to get rid of the control flow, so it's not
|
||||
// worth promoting to select instructions.
|
||||
BasicBlock *DomBlock = 0, *IfBlock1 = 0, *IfBlock2 = 0;
|
||||
if (CanPromote) {
|
||||
PN = cast<PHINode>(BB->begin());
|
||||
BasicBlock *Pred = PN->getIncomingBlock(0);
|
||||
if (cast<BranchInst>(Pred->getTerminator())->isUnconditional()) {
|
||||
IfBlock1 = Pred;
|
||||
DomBlock = *pred_begin(Pred);
|
||||
for (BasicBlock::iterator I = Pred->begin();
|
||||
!isa<TerminatorInst>(I); ++I)
|
||||
if (!AggressiveInsts.count(I)) {
|
||||
// This is not an aggressive instruction that we can promote.
|
||||
// Because of this, we won't be able to get rid of the control
|
||||
// flow, so the xform is not worth it.
|
||||
CanPromote = false;
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
Pred = PN->getIncomingBlock(1);
|
||||
if (CanPromote &&
|
||||
cast<BranchInst>(Pred->getTerminator())->isUnconditional()) {
|
||||
IfBlock2 = Pred;
|
||||
DomBlock = *pred_begin(Pred);
|
||||
for (BasicBlock::iterator I = Pred->begin();
|
||||
!isa<TerminatorInst>(I); ++I)
|
||||
if (!AggressiveInsts.count(I)) {
|
||||
// This is not an aggressive instruction that we can promote.
|
||||
// Because of this, we won't be able to get rid of the control
|
||||
// flow, so the xform is not worth it.
|
||||
CanPromote = false;
|
||||
break;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// If we can still promote the PHI nodes after this gauntlet of tests,
|
||||
// do all of the PHI's now.
|
||||
if (CanPromote) {
|
||||
// Move all 'aggressive' instructions, which are defined in the
|
||||
// conditional parts of the if's up to the dominating block.
|
||||
if (IfBlock1) {
|
||||
DomBlock->getInstList().splice(DomBlock->getTerminator(),
|
||||
IfBlock1->getInstList(),
|
||||
IfBlock1->begin(),
|
||||
IfBlock1->getTerminator());
|
||||
}
|
||||
if (IfBlock2) {
|
||||
DomBlock->getInstList().splice(DomBlock->getTerminator(),
|
||||
IfBlock2->getInstList(),
|
||||
IfBlock2->begin(),
|
||||
IfBlock2->getTerminator());
|
||||
}
|
||||
|
||||
while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
|
||||
// Change the PHI node into a select instruction.
|
||||
Value *TrueVal =
|
||||
PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse);
|
||||
Value *FalseVal =
|
||||
PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue);
|
||||
|
||||
std::string Name = PN->getName(); PN->setName("");
|
||||
PN->replaceAllUsesWith(new SelectInst(IfCond, TrueVal, FalseVal,
|
||||
Name, AfterPHIIt));
|
||||
BB->getInstList().erase(PN);
|
||||
}
|
||||
Changed = true;
|
||||
}
|
||||
}
|
||||
}
|
||||
if (PN->getNumIncomingValues() == 2)
|
||||
Changed |= FoldTwoEntryPHINode(PN);
|
||||
|
||||
return Changed;
|
||||
}
|
||||
|
||||
Loading…
Reference in New Issue
Block a user