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If there is an empty block between a source and its successor block, it still requires a unconditional branch. 

llvm-svn: 37344
This commit is contained in:
Evan Cheng 2007-05-29 22:31:16 +00:00
parent 5fba6c19b2
commit c2237ce217
1 changed files with 37 additions and 30 deletions
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67
llvm/lib/CodeGen/IfConversion.cpp
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@ -339,6 +339,14 @@ void IfConverter::InvalidatePreds(MachineBasicBlock *BB) {
}
}
/// InsertUncondBranch - Inserts an unconditional branch from BB to ToBB.
///
static void InsertUncondBranch(MachineBasicBlock *BB, MachineBasicBlock *ToBB,
const TargetInstrInfo *TII) {
std::vector<MachineOperand> NoCond;
TII->InsertBranch(*BB, ToBB, NULL, NoCond);
}
/// IfConvertEarlyExit - If convert a early exit sub-CFG.
///
bool IfConverter::IfConvertEarlyExit(BBInfo &BBI) {
@ -369,10 +377,8 @@ bool IfConverter::IfConvertEarlyExit(BBInfo &BBI) {
// unconditional one.
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
MergeBlocks(BBI, *CvtBBI);
if (!isNextBlock(BBI.BB, NextBBI->BB)) {
std::vector<MachineOperand> NoCond;
TII->InsertBranch(*BBI.BB, NextBBI->BB, NULL, NoCond);
}
if (!isNextBlock(BBI.BB, NextBBI->BB))
InsertUncondBranch(BBI.BB, NextBBI->BB, TII);
std::copy(NewCond.begin(), NewCond.end(), std::back_inserter(BBI.Predicate));
// Update block info. BB can be iteratively if-converted.
@ -430,8 +436,8 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
BBI.Kind = ICNotClassfied;
bool TrueNeedCBr;
bool FalseNeedCBr;
bool TrueNeedBr;
bool FalseNeedBr;
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
FeasibilityAnalysis(TrueBBI, BBI.BrCond);
@ -444,14 +450,14 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
if (Proceed) {
// 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 conditional branch to its successor.
TrueNeedCBr = !TrueBBI.TrueBB && BBI.TrueBB->succ_size();
FalseNeedCBr = !FalseBBI.TrueBB && BBI.FalseBB->succ_size();
if (TrueNeedCBr && TrueBBI.ModifyPredicate) {
// return. If it's the former, add a branch to its successor.
TrueNeedBr = !TrueBBI.TrueBB && BBI.TrueBB->succ_size();
FalseNeedBr = !FalseBBI.TrueBB && BBI.FalseBB->succ_size();
if (TrueNeedBr && TrueBBI.ModifyPredicate) {
TrueBBI.isPredicable = false;
Proceed = false;
}
if (FalseNeedCBr && FalseBBI.ModifyPredicate) {
if (FalseNeedBr && FalseBBI.ModifyPredicate) {
FalseBBI.isPredicable = false;
Proceed = false;
}
@ -502,32 +508,35 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB);
PredicateBlock(TrueBBI, BBI.BrCond);
// Add a conditional branch to 'true' successor if needed.
if (TrueNeedCBr && TrueBBI.ModifyPredicate &&
isNextBlock(BBI.TrueBB, *BBI.TrueBB->succ_begin()))
TrueNeedCBr = false;
if (TrueNeedCBr)
TII->InsertBranch(*BBI.TrueBB, *BBI.TrueBB->succ_begin(), NULL, BBI.BrCond);
// Predicate the 'false' block.
PredicateBlock(FalseBBI, RevCond, true);
// Add a conditional branch to 'false' successor if needed.
if (FalseNeedCBr && !TrueBBI.ModifyPredicate &&
isNextBlock(BBI.FalseBB, *BBI.FalseBB->succ_begin()))
FalseNeedCBr = false;
if (FalseNeedCBr)
TII->InsertBranch(*BBI.FalseBB, *BBI.FalseBB->succ_begin(), NULL,
RevCond);
// 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 *CvtBBI;
if (!TrueBBI.ModifyPredicate) {
// Add a conditional branch from 'true' to 'true' successor if needed.
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 {
// 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;
}
@ -543,10 +552,8 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
MergeBlocks(BBI, *CvtBBI);
CvtBBI = &BBI;
OkToIfcvt = false;
} else {
std::vector<MachineOperand> NoCond;
TII->InsertBranch(*BBI.BB, CvtBBI->BB, NULL, NoCond);
}
} else
InsertUncondBranch(BBI.BB, CvtBBI->BB, TII);
// If the if-converted block fallthrough into the tail block, then
// fold the tail block in as well.