Don't crash on extra evil irreducible control flow.

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

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/CodeGen/MachineTraceMetrics.cpp b/lib/CodeGen/MachineTraceMetrics.cpp
index 9b91af541d..b3abec76bc 100644
--- a/lib/CodeGen/MachineTraceMetrics.cpp
+++ b/lib/CodeGen/MachineTraceMetrics.cpp
@@ -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;