[llvm] Add option to log debugging to stdout (PR #91533)

[David Blaikie via llvm-commits]

================
@@ -161,31 +166,39 @@ static void debug_user_sig_handler(void *Cookie) {
 
 /// dbgs - Return a circular-buffered debug stream.
 raw_ostream &llvm::dbgs() {
-  // Do one-time initialization in a thread-safe way.
-  static struct dbgstream {
-    circular_raw_ostream strm;
-
-    dbgstream()
-        : strm(errs(), "*** Debug Log Output ***\n",
-               (!EnableDebugBuffering || !DebugFlag) ? 0 : *DebugBufferSize) {
-      if (EnableDebugBuffering && DebugFlag && *DebugBufferSize != 0)
-        // TODO: Add a handler for SIGUSER1-type signals so the user can
-        // force a debug dump.
-        sys::AddSignalHandler(&debug_user_sig_handler, nullptr);
-      // Otherwise we've already set the debug stream buffer size to
-      // zero, disabling buffering so it will output directly to errs().
-    }
-  } thestrm;
-
-  return thestrm.strm;
+  if (LogDebugToStdOut) {
+    return outs();
+  } else {
----------------
dwblaikie wrote:

Generally LLVM omits {} on single-line if statements, and avoids else-after-return, so this would be:
```
if (LogDebugToStdOut)
  return outs();
static struct dbgstream {
  ...
};
return thstrm.strm;
```

https://github.com/llvm/llvm-project/pull/91533