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Whitespace changes, comment clarification. No functional changes.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91274 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2009-12-14 06:51:19 +00:00
parent a937f220e1
commit 85de1e5bad
3 changed files with 33 additions and 23 deletions
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9
include/llvm/Target/TargetInstrInfo.h
View File

@ -286,11 +286,10 @@ public:
/// just return false, leaving TBB/FBB null.
/// 2. If this block ends with only an unconditional branch, it sets TBB to be
/// the destination block.
/// 3. If this block ends with an conditional branch and it falls through to
/// a successor block, it sets TBB to be the branch destination block and
/// a list of operands that evaluate the condition. These
/// operands can be passed to other TargetInstrInfo methods to create new
/// branches.
/// 3. If this block ends with a conditional branch and it falls through to a
/// successor block, it sets TBB to be the branch destination block and a
/// list of operands that evaluate the condition. These operands can be
/// passed to other TargetInstrInfo methods to create new branches.
/// 4. If this block ends with a conditional branch followed by an
/// unconditional branch, it returns the 'true' destination in TBB, the
/// 'false' destination in FBB, and a list of operands that evaluate the

6
lib/CodeGen/MachineBasicBlock.cpp
View File

@ -483,16 +483,16 @@ bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
MachineFunction::iterator FallThru =
llvm::next(MachineFunction::iterator(this));
// If this block ends with a conditional branch that falls through to its
// successor, set DestB as the successor.
if (isCond) {
// If this block ends with a conditional branch that falls through to its
// successor, set DestB as the successor.
if (DestB == 0 && FallThru != getParent()->end()) {
DestB = FallThru;
AddedFallThrough = true;
}
} else {
// If this is an unconditional branch with no explicit dest, it must just be
// a fallthrough into DestB.
// a fallthrough into DestA.
if (DestA == 0 && FallThru != getParent()->end()) {
DestA = FallThru;
AddedFallThrough = true;

41
lib/Target/X86/X86InstrInfo.cpp
View File

@ -1624,14 +1624,17 @@ bool X86InstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,
MachineBasicBlock::iterator I = MBB.end();
while (I != MBB.begin()) {
--I;
// Working from the bottom, when we see a non-terminator
// instruction, we're done.
// Working from the bottom, when we see a non-terminator instruction, we're
// done.
if (!isBrAnalysisUnpredicatedTerminator(I, *this))
break;
// A terminator that isn't a branch can't easily be handled
// by this analysis.
// A terminator that isn't a branch can't easily be handled by this
// analysis.
if (!I->getDesc().isBranch())
return true;
// Handle unconditional branches.
if (I->getOpcode() == X86::JMP) {
if (!AllowModify) {
@ -1642,8 +1645,10 @@ bool X86InstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,
// If the block has any instructions after a JMP, delete them.
while (llvm::next(I) != MBB.end())
llvm::next(I)->eraseFromParent();
Cond.clear();
FBB = 0;
// Delete the JMP if it's equivalent to a fall-through.
if (MBB.isLayoutSuccessor(I->getOperand(0).getMBB())) {
TBB = 0;
@ -1651,14 +1656,17 @@ bool X86InstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,
I = MBB.end();
continue;
}
// TBB is used to indicate the unconditinal destination.
TBB = I->getOperand(0).getMBB();
continue;
}
// Handle conditional branches.
X86::CondCode BranchCode = GetCondFromBranchOpc(I->getOpcode());
if (BranchCode == X86::COND_INVALID)
return true; // Can't handle indirect branch.
// Working from the bottom, handle the first conditional branch.
if (Cond.empty()) {
FBB = TBB;
@ -1666,24 +1674,26 @@ bool X86InstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,
Cond.push_back(MachineOperand::CreateImm(BranchCode));
continue;
}
// Handle subsequent conditional branches. Only handle the case
// where all conditional branches branch to the same destination
// and their condition opcodes fit one of the special
// multi-branch idioms.
// Handle subsequent conditional branches. Only handle the case where all
// conditional branches branch to the same destination and their condition
// opcodes fit one of the special multi-branch idioms.
assert(Cond.size() == 1);
assert(TBB);
// Only handle the case where all conditional branches branch to
// the same destination.
// Only handle the case where all conditional branches branch to the same
// destination.
if (TBB != I->getOperand(0).getMBB())
return true;
X86::CondCode OldBranchCode = (X86::CondCode)Cond[0].getImm();
// If the conditions are the same, we can leave them alone.
X86::CondCode OldBranchCode = (X86::CondCode)Cond[0].getImm();
if (OldBranchCode == BranchCode)
continue;
// If they differ, see if they fit one of the known patterns.
// Theoretically we could handle more patterns here, but
// we shouldn't expect to see them if instruction selection
// has done a reasonable job.
// If they differ, see if they fit one of the known patterns. Theoretically,
// we could handle more patterns here, but we shouldn't expect to see them
// if instruction selection has done a reasonable job.
if ((OldBranchCode == X86::COND_NP &&
BranchCode == X86::COND_E) ||
(OldBranchCode == X86::COND_E &&
@ -1696,6 +1706,7 @@ bool X86InstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,
BranchCode = X86::COND_NE_OR_P;
else
return true;
// Update the MachineOperand.
Cond[0].setImm(BranchCode);
}