[llvm] [llvm-profgen] Ignore inline frames with an emtpy function name (PR #66678)

[Hongtao Yu via llvm-commits]

https://github.com/htyu created https://github.com/llvm/llvm-project/pull/66678

Broken debug information can give empty names for an inlined frame, e.g,
```

0x1d605c68: ryKeyINS7_17SmartCounterTypesEEESt10shared_ptrINS7_15AsyncCacheValueIS9_EEESaIhESt6atomicEEE9fetch_subElSt12memory_order at   Filename: edata.h
  Function start filename: edata.h
  Function start line: 266
  Function start address: 0x1d605c68
  Line: 267
  Column: 0
 (inlined by)  at   Filename: edata.h
  Function start filename: edata.h
  Function start line: 274
  Function start address: 0x1d605c68
  Line: 275
  Column: 0
 (inlined by) _EEEmmEv at   Filename: arena.c
  Function start filename: arena.c
  Function start line: 1303
  Line: 1308
  Column: 0
```

This patch avoids creating a sample context with an empty function name by stopping tracking at that frame. This prevents a hash failure that leads to an ICE, where empty context serves at an empty key for the underlying MapVector https://github.com/llvm/llvm-project/blob/7624de5beae2f142abfdb3e32a63c263a586d768/llvm/lib/ProfileData/SampleProfWriter.cpp#L261

>From 092820cd3d70afccd89a4a94ac8472770db2268a Mon Sep 17 00:00:00 2001
From: Hongtao Yu <hoy at fb.com>
Date: Mon, 18 Sep 2023 10:33:19 -0700
Subject: [PATCH] [llvm-profgen] Ignore inline frames with an emtpy function
 name

---
 llvm/include/llvm/ProfileData/SampleProf.h | 4 +++-
 llvm/tools/llvm-profgen/ProfiledBinary.cpp | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/llvm/include/llvm/ProfileData/SampleProf.h b/llvm/include/llvm/ProfileData/SampleProf.h
index 9b2416e39b6cc9a..78a16499accd64a 100644
--- a/llvm/include/llvm/ProfileData/SampleProf.h
+++ b/llvm/include/llvm/ProfileData/SampleProf.h
@@ -533,7 +533,9 @@ class SampleContext {
   SampleContext() : State(UnknownContext), Attributes(ContextNone) {}
 
   SampleContext(StringRef Name)
-      : Name(Name), State(UnknownContext), Attributes(ContextNone) {}
+      : Name(Name), State(UnknownContext), Attributes(ContextNone) {
+        assert(!Name.empty() && "Name is empty");
+      }
 
   SampleContext(SampleContextFrames Context,
                 ContextStateMask CState = RawContext)
diff --git a/llvm/tools/llvm-profgen/ProfiledBinary.cpp b/llvm/tools/llvm-profgen/ProfiledBinary.cpp
index 5fb51d3ac9eba78..f26b2bd5df5eda5 100644
--- a/llvm/tools/llvm-profgen/ProfiledBinary.cpp
+++ b/llvm/tools/llvm-profgen/ProfiledBinary.cpp
@@ -865,7 +865,7 @@ SampleContextFrameVector ProfiledBinary::symbolize(const InstructionPointer &IP,
   SampleContextFrameVector CallStack;
   for (int32_t I = InlineStack.getNumberOfFrames() - 1; I >= 0; I--) {
     const auto &CallerFrame = InlineStack.getFrame(I);
-    if (CallerFrame.FunctionName == "<invalid>")
+    if (CallerFrame.FunctionName.empty() || (CallerFrame.FunctionName == "<invalid>"))
       break;
 
     StringRef FunctionName(CallerFrame.FunctionName);