use valid bits to avoid unnecessary machine trace metric recomputations

Although this does cut the number of traces recomputed by ~10% for the
test case mentioned in http://reviews.llvm.org/D10460, it doesn't
make a dent in the overall performance. That example needs to be more
selective when invalidating traces.

llvm-svn: 241393

1 files changed, 10 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/MachineTraceMetrics.cpp b/llvm/lib/CodeGen/MachineTraceMetrics.cpp
index f9adba0..10a984c 100644
--- a/llvm/lib/CodeGen/MachineTraceMetrics.cpp
+++ b/llvm/lib/CodeGen/MachineTraceMetrics.cpp
@@ -1131,11 +1131,16 @@ computeInstrHeights(const MachineBasicBlock *MBB) {
 
 MachineTraceMetrics::Trace
 MachineTraceMetrics::Ensemble::getTrace(const MachineBasicBlock *MBB) {
-  // FIXME: Check cache tags, recompute as needed.
-  computeTrace(MBB);
-  computeInstrDepths(MBB);
-  computeInstrHeights(MBB);
-  return Trace(*this, BlockInfo[MBB->getNumber()]);
+  TraceBlockInfo &TBI = BlockInfo[MBB->getNumber()];
+
+  if (!TBI.hasValidDepth() || !TBI.hasValidHeight())
+    computeTrace(MBB);
+  if (!TBI.HasValidInstrDepths)
+    computeInstrDepths(MBB);
+  if (!TBI.HasValidInstrHeights)
+    computeInstrHeights(MBB);
+  
+  return Trace(*this, TBI);
 }
 
 unsigned