diff options
Diffstat (limited to 'include/llvm')
| -rw-r--r-- | include/llvm/CodeGen/MachineTraceMetrics.h | 23 |
1 files changed, 18 insertions, 5 deletions
diff --git a/include/llvm/CodeGen/MachineTraceMetrics.h b/include/llvm/CodeGen/MachineTraceMetrics.h index 460730b..eaaa70a 100644 --- a/include/llvm/CodeGen/MachineTraceMetrics.h +++ b/include/llvm/CodeGen/MachineTraceMetrics.h @@ -165,12 +165,25 @@ public: /// Invalidate height resources when a block below this one has changed. void invalidateHeight() { InstrHeight = ~0u; HasValidInstrHeights = false; } - /// Determine if this block belongs to the same trace as TBI and comes - /// before it in the trace. + /// Assuming that this is a dominator of TBI, determine if it contains + /// useful instruction depths. A dominating block can be above the current + /// trace head, and any dependencies from such a far away dominator are not + /// expected to affect the critical path. + /// /// Also returns true when TBI == this. - bool isEarlierInSameTrace(const TraceBlockInfo &TBI) const { - return hasValidDepth() && TBI.hasValidDepth() && - Head == TBI.Head && InstrDepth <= TBI.InstrDepth; + bool isUsefulDominator(const TraceBlockInfo &TBI) const { + // The trace for TBI may not even be calculated yet. + if (!hasValidDepth() || !TBI.hasValidDepth()) + return false; + // Instruction depths are only comparable if the traces share a head. + if (Head != TBI.Head) + return false; + // It is almost always the case that TBI belongs to the same trace as + // this block, but rare convoluted cases involving irreducible control + // flow, a dominator may share a trace head without actually being on the + // same trace as TBI. This is not a big problem as long as it doesn't + // increase the instruction depth. + return HasValidInstrDepths && InstrDepth <= TBI.InstrDepth; } // Data-dependency-related information. Per-instruction depth and height |