[PATCH] D123361: [llvm-profgen] Filter out oversized LBR ranges.

[Hongtao Yu via Phabricator via llvm-commits]

hoy created this revision.
Herald added subscribers: modimo, wenlei.
Herald added a project: All.
hoy requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Test Plan:


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D123361

Files:
  llvm/tools/llvm-profgen/PerfReader.cpp
  llvm/tools/llvm-profgen/PerfReader.h


Index: llvm/tools/llvm-profgen/PerfReader.h
===================================================================
--- llvm/tools/llvm-profgen/PerfReader.h
+++ llvm/tools/llvm-profgen/PerfReader.h
@@ -217,6 +217,14 @@
 
 using SampleVector = SmallVector<std::tuple<uint64_t, uint64_t, uint64_t>, 16>;
 
+
+inline bool isValidLBRRange(uint64_t Start, uint64_t End)
+{
+  // Start bigger than End is considered invalid.
+  // Larger LBR ranges are also assumed invalid.
+  return Start <= End && End <= Start +  (1 << 20);
+}
+
 // The state for the unwinder, it doesn't hold the data but only keep the
 // pointer/index of the data, While unwinding, the CallStack is changed
 // dynamicially and will be recorded as the context of the sample
Index: llvm/tools/llvm-profgen/PerfReader.cpp
===================================================================
--- llvm/tools/llvm-profgen/PerfReader.cpp
+++ llvm/tools/llvm-profgen/PerfReader.cpp
@@ -100,7 +100,7 @@
   InstructionPointer &IP = State.InstPtr;
   uint64_t Target = State.getCurrentLBRTarget();
   uint64_t End = IP.Address;
-  if (Target > End) {
+  if (!isValidLBRRange(Target, End)) {
     // Skip unwinding the rest of LBR trace when a bogus range is seen.
     State.setInvalid();
     return;
@@ -932,7 +932,7 @@
     // LBR and FROM of next LBR.
     uint64_t StartOffset = TargetOffset;
     if (EndOffeset != 0) {
-      if (StartOffset <= EndOffeset)
+      if (isValidLBRRange(StartOffset, EndOffeset))
         Counter.recordRangeCount(StartOffset, EndOffeset, Repeat);
     }
     EndOffeset = SourceOffset;
@@ -1179,7 +1179,7 @@
   const char *RangeCrossFuncMsg =
       "Fall through range should not cross function boundaries, likely due to "
       "profile and binary mismatch.";
-  const char *BogusRangeMsg = "Range start is after range end.";
+  const char *BogusRangeMsg = "Range start is after or too far from range end.";
 
   uint64_t TotalRangeNum = 0;
   uint64_t InstNotBoundary = 0;
@@ -1210,7 +1210,7 @@
       WarnInvalidRange(StartOffset, EndOffset, RangeCrossFuncMsg);
     }
 
-    if (StartOffset > EndOffset) {
+    if (!isValidLBRRange(StartOffset, EndOffset)) {
       BogusRange += I.second;
       WarnInvalidRange(StartOffset, EndOffset, BogusRangeMsg);
     }
@@ -1225,9 +1225,9 @@
   emitWarningSummary(
       RangeCrossFunc, TotalRangeNum,
       "of samples are from ranges that do cross function boundaries.");
-  emitWarningSummary(
-      BogusRange, TotalRangeNum,
-      "of samples are from ranges that have range start after range end.");
+  emitWarningSummary(BogusRange, TotalRangeNum,
+                     "of samples are from ranges that have range start after "
+                     "or too far from range end.");
 }
 
 void PerfScriptReader::parsePerfTraces() {


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D123361.421423.patch
Type: text/x-patch
Size: 2779 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20220408/fcc8f5c7/attachment.bin>