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Fix a couple of typos and be smarter about order of blocks when ifcvt a diamond. 

llvm-svn: 37449
This commit is contained in:
Evan Cheng 2007-06-06 00:57:55 +00:00
parent 3c6ab49051
commit 30565998bb
1 changed files with 30 additions and 17 deletions
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47
llvm/lib/CodeGen/IfConversion.cpp
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@ -308,8 +308,8 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
} else {
// FIXME: Consider duplicating if BB is small.
bool TryTriangle = TrueBBI.TrueBB && TrueBBI.TrueBB == BBI.FalseBB &&
BBI.TrueBB->pred_size() == 1;
bool TrySimple = TrueBBI.BrCond.size() == 0 && BBI.TrueBB->pred_size() == 1;
TrueBBI.BB->pred_size() == 1;
bool TrySimple = TrueBBI.BrCond.size() == 0 && TrueBBI.BB->pred_size() == 1;
if ((TryTriangle || TrySimple) &&
FeasibilityAnalysis(TrueBBI, BBI.BrCond)) {
if (TryTriangle) {
@ -333,14 +333,21 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
BBI.Kind = ICSimple;
TrueBBI.Kind = ICChild;
}
} else if (FalseBBI.BrCond.size() == 0 && BBI.FalseBB->pred_size() == 1) {
// Try 'simple' on the other path...
} else if (FalseBBI.BrCond.size() == 0 && FalseBBI.BB->pred_size() == 1) {
// Try the other path...
std::vector<MachineOperand> RevCond(BBI.BrCond);
if (TII->ReverseBranchCondition(RevCond))
assert(false && "Unable to reverse branch condition!");
if (FeasibilityAnalysis(FalseBBI, RevCond)) {
BBI.Kind = ICSimpleFalse;
FalseBBI.Kind = ICChild;
if (!TII->ReverseBranchCondition(RevCond) &&
FeasibilityAnalysis(FalseBBI, RevCond)) {
if (FalseBBI.TrueBB && FalseBBI.TrueBB == BBI.TrueBB &&
FalseBBI.BB->pred_size() == 1) {
// Reverse 'true' and 'false' paths.
ReverseBranchCondition(BBI);
BBI.Kind = ICTriangle;
FalseBBI.Kind = ICChild;
} else {
BBI.Kind = ICSimpleFalse;
FalseBBI.Kind = ICChild;
}
}
}
}
@ -620,16 +627,19 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
TII->ReverseBranchCondition(RevCond);
std::vector<MachineOperand> *Cond1 = &BBI.BrCond;
std::vector<MachineOperand> *Cond2 = &RevCond;
if (TrueBBI.ModifyPredicate) {
std::swap(BBI1, BBI2);
std::swap(Cond1, Cond2);
}
// Check the 'true' and 'false' blocks if either isn't ended with a branch.
// Either the block fallthrough to another block or it ends with a
// return. If it's the former, add a branch to its successor.
bool NeedBr1 = !BBI1->TrueBB && BBI1->BB->succ_size();
bool NeedBr2 = !BBI2->TrueBB && BBI1->BB->succ_size();
bool NeedBr2 = !BBI2->TrueBB && BBI2->BB->succ_size();
if ((TrueBBI.ModifyPredicate && !FalseBBI.ModifyPredicate) ||
(!TrueBBI.ModifyPredicate && !FalseBBI.ModifyPredicate &&
NeedBr1 && !NeedBr2)) {
std::swap(BBI1, BBI2);
std::swap(Cond1, Cond2);
std::swap(NeedBr1, NeedBr2);
}
// Predicate the 'true' block after removing its branch.
BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB);
@ -650,8 +660,6 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
// Keep them as two separate blocks if there is an early exit.
if (!NeedBr1)
MergeBlocks(*BBI1, *BBI2);
else if (!isNextBlock(BBI1->BB, BBI2->BB))
InsertUncondBranch(BBI1->BB, BBI2->BB, TII);
// Remove the conditional branch from entry to the blocks.
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
@ -659,6 +667,11 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
// Merge the combined block into the entry of the diamond.
MergeBlocks(BBI, *BBI1);
// 'True' and 'false' aren't combined, see if we need to add a unconditional
// branch to the 'false' block.
if (NeedBr1 && !isNextBlock(BBI.BB, BBI2->BB))
InsertUncondBranch(BBI1->BB, BBI2->BB, TII);
// If the if-converted block fallthrough or unconditionally branch into the
// tail block, and the tail block does not have other predecessors, then
// fold the tail block in as well.