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Don't try to split weird critical edges that really aren't:

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BB#1: derived from LLVM BB %bb.nph28
    Live Ins: %AL
    Predecessors according to CFG: BB#0
	TEST8rr %reg16384<kill>, %reg16384, %EFLAGS<imp-def>; GR8:%reg16384
	JNE_4 <BB#2>, %EFLAGS<imp-use,kill>
	JMP_4 <BB#2>
    Successors according to CFG: BB#2 BB#2

These double CFG edges only ever occur in bugpoint-generated code, so there is
no need to attempt something clever.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117992 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2010-11-02 00:58:37 +00:00
parent e85bd773e6
commit 371e82bf51
1 changed files with 12 additions and 2 deletions
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14
lib/CodeGen/MachineBasicBlock.cpp
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@ -450,14 +450,24 @@ MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
MachineFunction *MF = getParent(); MachineFunction *MF = getParent();
DebugLoc dl; // FIXME: this is nowhere DebugLoc dl; // FIXME: this is nowhere
// We may need to update this's terminator, but we can't do that if AnalyzeBranch // We may need to update this's terminator, but we can't do that if
// fails. If this uses a jump table, we won't touch it. // AnalyzeBranch fails. If this uses a jump table, we won't touch it.
const TargetInstrInfo *TII = MF->getTarget().getInstrInfo(); const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
MachineBasicBlock *TBB = 0, *FBB = 0; MachineBasicBlock *TBB = 0, *FBB = 0;
SmallVector<MachineOperand, 4> Cond; SmallVector<MachineOperand, 4> Cond;
if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) if (TII->AnalyzeBranch(*this, TBB, FBB, Cond))
return NULL; return NULL;
// Avoid bugpoint weirdness: A block may end with a conditional branch but
// jumps to the same MBB is either case. We have duplicate CFG edges in that
// case that we can't handle. Since this never happens in properly optimized
// code, just skip those edges.
if (TBB && TBB == FBB) {
DEBUG(dbgs() << "Won't split critical edge after degenerate BB#"
<< getNumber() << '\n');
return NULL;
}
MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock(); MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB); MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB);
DEBUG(dbgs() << "Splitting critical edge:" DEBUG(dbgs() << "Splitting critical edge:"