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Don't crash on extra evil irreducible control flow.

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When the CFG contains a loop with multiple entry blocks, the traces
computed by MachineTraceMetrics don't always have the same nice
properties. Loop back-edges are normally excluded from traces, but
MachineLoopInfo doesn't recognize loops with multiple entry blocks, so
those back-edges may be included.

Avoid asserting when that happens by adding an isEarlierInSameTrace()
function that accurately determines if a dominating block is part of the
same trace AND is above the currrent block in the trace.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165434 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen
2012-10-08 22:06:44 +00:00
parent 8e635dbc78
commit 6be75ae196
3 changed files with 85 additions and 2 deletions
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4
lib/CodeGen/MachineTraceMetrics.cpp
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@ -677,7 +677,7 @@ computeCrossBlockCriticalPath(const TraceBlockInfo &TBI) {
const MachineInstr *DefMI = MTM.MRI->getVRegDef(LIR.Reg);
// Ignore dependencies outside the current trace.
const TraceBlockInfo &DefTBI = BlockInfo[DefMI->getParent()->getNumber()];
if (!DefTBI.hasValidDepth() || DefTBI.Head != TBI.Head)
if (!DefTBI.isEarlierInSameTrace(TBI))
continue;
unsigned Len = LIR.Height + Cycles[DefMI].Depth;
MaxLen = std::max(MaxLen, Len);
@ -740,7 +740,7 @@ computeInstrDepths(const MachineBasicBlock *MBB) {
const TraceBlockInfo&DepTBI =
BlockInfo[Dep.DefMI->getParent()->getNumber()];
// Ignore dependencies from outside the current trace.
if (!DepTBI.hasValidDepth() || DepTBI.Head != TBI.Head)
if (!DepTBI.isEarlierInSameTrace(TBI))
continue;
assert(DepTBI.HasValidInstrDepths && "Inconsistent dependency");
unsigned DepCycle = Cycles.lookup(Dep.DefMI).Depth;