[CSSPGO][llvm-profgen] Handle return to external transition.

htyu · htyu · commit 5c8659801a49 · 2021-06-22T16:24:59.000-07:00
In a callback case, a return from internal code, say A, to external runtime can happen. The external runtime can then call back to another internal routine, say B. Making an artificial branch that looks like a return from A to B can confuse the unwinder to treat the instruction before B as the call instruction. Reviewed By: wenlei, wmi Differential Revision: https://reviews.llvm.org/D104546
diff --git a/llvm/tools/llvm-profgen/PerfReader.cpp b/llvm/tools/llvm-profgen/PerfReader.cpp
@@ -460,6 +460,16 @@ bool PerfReader::extractLBRStack(TraceStream &TraceIt,
         // they are likely in different contexts.
         break;
       }
+
+      if (Binary->addressIsReturn(Src)) {
+        // In a callback case, a return from internal code, say A, to external
+        // runtime can happen. The external runtime can then call back to
+        // another internal routine, say B. Making an artificial branch that
+        // looks like a return from A to B can confuse the unwinder to treat
+        // the instruction before B as the call instruction.
+        break;
+      }
+
       // For transition to external code, group the Source with the next
       // availabe transition target.
       Dst = PrevTrDst;
