From 371e82bf513778bf2bde4c3eebe9407af2cef21f Mon Sep 17 00:00:00 2001 From: Jakob Stoklund Olesen Date: Tue, 2 Nov 2010 00:58:37 +0000 Subject: [PATCH] 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, %reg16384, %EFLAGS; GR8:%reg16384 JNE_4 , %EFLAGS JMP_4 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 --- lib/CodeGen/MachineBasicBlock.cpp | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp index d4f901d7933..31d12ebdc47 100644 --- a/lib/CodeGen/MachineBasicBlock.cpp +++ b/lib/CodeGen/MachineBasicBlock.cpp @@ -450,14 +450,24 @@ MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) { 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 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:" -- 2.34.1