[llvm] [llvm-profgen][SPGO] Support profiles with multiple concurrent processes (PR #169353)

[Wei Wang via llvm-commits]

================
@@ -1169,15 +1263,24 @@ bool PerfScriptReader::isMMapEvent(StringRef Line) {
   if (Line.empty() || Line.size() < 50)
     return false;
 
-  if (std::isdigit(Line[0]))
-    return false;
+  if (MultiProcessProfile) {
+    // Trim off the first numeric field, which is the PID.
+    // Make sure not to trim other numeric fields.
+    auto Trimmed = Line.ltrim().ltrim("0123456789").ltrim();
+
+    if (Trimmed.empty() || std::isdigit(Trimmed[0]))
+      return false;
+  } else {
+    if (std::isdigit(Line[0]))
+      return false;
+  }
----------------
apolloww wrote:

nit

```suggestion
  auto Trimmed = Line;
  if (MultiProcessProfile)
    // Trim off the first numeric field, which is the PID.
    // Make sure not to trim other numeric fields.
    Trimmed = Line.ltrim().ltrim("0123456789").ltrim();

  if (Trimmed.empty() || std::isdigit(Trimmed[0]))
    return false;
```

https://github.com/llvm/llvm-project/pull/169353