[llvm-commits] [llvm] r117992 - /llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp
Jakob Stoklund Olesen
stoklund at 2pi.dk
Mon Nov 1 17:58:37 PDT 2010
Author: stoklund
Date: Mon Nov 1 19:58:37 2010
New Revision: 117992
URL: http://llvm.org/viewvc/llvm-project?rev=117992&view=rev
Log:
Don't try to split weird critical edges that really aren't:
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.
Modified:
llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp
Modified: llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp?rev=117992&r1=117991&r2=117992&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp Mon Nov 1 19:58:37 2010
@@ -450,14 +450,24 @@
MachineFunction *MF = getParent();
DebugLoc dl; // FIXME: this is nowhere
- // We may need to update this's terminator, but we can't do that if AnalyzeBranch
- // fails. If this uses a jump table, we won't touch it.
+ // We may need to update this's terminator, but we can't do that if
+ // AnalyzeBranch fails. If this uses a jump table, we won't touch it.
const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
MachineBasicBlock *TBB = 0, *FBB = 0;
SmallVector<MachineOperand, 4> Cond;
if (TII->AnalyzeBranch(*this, TBB, FBB, Cond))
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();
MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB);
DEBUG(dbgs() << "Splitting critical edge:"
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