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Fix diamond shape ifcvt bugs.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37444 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2007-06-05 23:46:14 +00:00
parent 1d4eb6ab0d
commit 993fc9594e
1 changed files with 41 additions and 61 deletions
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102
lib/CodeGen/IfConversion.cpp
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@ -284,7 +284,7 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
}
} else if (TrueBBI.TrueBB == FalseBBI.TrueBB && CanRevCond &&
TrueBBI.BB->pred_size() == 1 &&
TrueBBI.BB->pred_size() == 1 &&
FalseBBI.BB->pred_size() == 1 &&
// Check the 'true' and 'false' blocks if either isn't ended with
// a branch. If the block does not fallthrough to another block
// then we need to add a branch to its successor.
@ -301,7 +301,7 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
// TBB FBB
// \ /
// TailBB
// Note MBB can be empty in case both TBB and FBB are return blocks.
// Note TailBB can be empty.
BBI.Kind = ICDiamond;
TrueBBI.Kind = FalseBBI.Kind = ICChild;
BBI.TailBB = TrueBBI.TrueBB;
@ -611,74 +611,58 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
--TrueBBI.NonPredSize;
}
// 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 TrueNeedBr = !TrueBBI.TrueBB && BBI.TrueBB->succ_size();
bool FalseNeedBr = !FalseBBI.TrueBB && BBI.FalseBB->succ_size();
// Merge the 'true' and 'false' blocks by copying the instructions
// from the 'false' block to the 'true' block. That is, unless the true
// block would clobber the predicate, in that case, do the opposite.
BBInfo *BBI1 = &TrueBBI;
BBInfo *BBI2 = &FalseBBI;
std::vector<MachineOperand> RevCond(BBI.BrCond);
TII->ReverseBranchCondition(RevCond);
BBInfo *CvtBBI;
if (!TrueBBI.ModifyPredicate) {
// Predicate the 'true' block after removing its branch.
TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB);
PredicateBlock(TrueBBI, BBI.BrCond);
// Predicate the 'false' block.
PredicateBlock(FalseBBI, RevCond, true);
if (TrueNeedBr)
TII->InsertBranch(*BBI.TrueBB, *BBI.TrueBB->succ_begin(), NULL,
BBI.BrCond);
// Add an unconditional branch from 'false' to to 'false' successor if it
// will not be the fallthrough block.
if (FalseNeedBr &&
!isNextBlock(BBI.BB, *BBI.FalseBB->succ_begin()))
InsertUncondBranch(BBI.FalseBB, *BBI.FalseBB->succ_begin(), TII);
MergeBlocks(TrueBBI, FalseBBI);
CvtBBI = &TrueBBI;
} else {
// Predicate the 'false' block after removing its branch.
FalseBBI.NonPredSize -= TII->RemoveBranch(*BBI.FalseBB);
PredicateBlock(FalseBBI, RevCond);
// Predicate the 'false' block.
PredicateBlock(TrueBBI, BBI.BrCond, true);
// Add a conditional branch from 'false' to 'false' successor if needed.
if (FalseNeedBr)
TII->InsertBranch(*BBI.FalseBB, *BBI.FalseBB->succ_begin(), NULL,
RevCond);
// Add an unconditional branch from 'true' to to 'true' successor if it
// will not be the fallthrough block.
if (TrueNeedBr &&
!isNextBlock(BBI.BB, *BBI.TrueBB->succ_begin()))
InsertUncondBranch(BBI.TrueBB, *BBI.TrueBB->succ_begin(), TII);
MergeBlocks(FalseBBI, TrueBBI);
CvtBBI = &FalseBBI;
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();
// Predicate the 'true' block after removing its branch.
BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB);
PredicateBlock(*BBI1, *Cond1);
// Add an early exit branch if needed.
if (NeedBr1)
TII->InsertBranch(*BBI1->BB, *BBI1->BB->succ_begin(), NULL, *Cond1);
// Predicate the 'false' block.
PredicateBlock(*BBI2, *Cond2, true);
// Add an unconditional branch from 'false' to to 'false' successor if it
// will not be the fallthrough block.
if (NeedBr2 && !isNextBlock(BBI2->BB, *BBI2->BB->succ_begin()))
InsertUncondBranch(BBI2->BB, *BBI2->BB->succ_begin(), TII);
// 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);
bool OkToIfcvt = true;
// Merge the combined block into the entry of the diamond if the entry
// block is its only predecessor. Otherwise, insert an unconditional
// branch from entry to the if-converted block.
if (CvtBBI->BB->pred_size() == 1) {
MergeBlocks(BBI, *CvtBBI);
CvtBBI = &BBI;
OkToIfcvt = false;
} else if (!isNextBlock(BBI.BB, CvtBBI->BB))
InsertUncondBranch(BBI.BB, CvtBBI->BB, TII);
// Merge the combined block into the entry of the diamond.
MergeBlocks(BBI, *BBI1);
// 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.
BBInfo *CvtBBI = NeedBr1 ? BBI2 : &BBI;
if (BBI.TailBB &&
BBI.TailBB->pred_size() == 1 && CvtBBI->BB->succ_size() == 1) {
CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB);
@ -687,11 +671,7 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
TailBBI.Kind = ICDead;
}
// Update block info. BB may be iteratively if-converted.
if (OkToIfcvt) {
BBI.Kind = ICReAnalyze;
ReTryPreds(BBI.BB);
}
// Update block info.
TrueBBI.Kind = ICDead;
FalseBBI.Kind = ICDead;