[Support] Accept Twine in debugHeader

Accept `Twine`s in `circt::debugHeader`, which makes using the function
a bit easier. Also, rely on the `raw_ostream`'s buffer location tracking
to figure out how many padding characters need to be added.

Author: fabianschuiki

include/circt/Support/Debug.h

@@ -25,7 +25,7 @@ namespace circt {
 ///
 /// This is commonly used for generating a header in debug information.  The
 /// format is modeled after LLVM/MLIR/CIRCT source file headers.
-llvm::raw_ostream &debugHeader(llvm::StringRef str, int width = 80);
+llvm::raw_ostream &debugHeader(const llvm::Twine &str, unsigned width = 80);
 
 /// Write a boilerplate header for a pass to the debug stream.  This generates
 /// output like the following if the pass's name is "FooPass":
@@ -34,13 +34,13 @@ llvm::raw_ostream &debugHeader(llvm::StringRef str, int width = 80);
 ///
 /// This is commonly used to generate a header in debug when a pass starts
 /// running.
-llvm::raw_ostream &debugPassHeader(const mlir::Pass *pass, int width = 80);
+llvm::raw_ostream &debugPassHeader(const mlir::Pass *pass, unsigned width = 80);
 
 /// Write a boilerplate footer to the debug stream to indicate that a pass has
 /// ended.  This produces text like the following:
 ///
 ///    ===-----------------------------------===
-llvm::raw_ostream &debugFooter(int width = 80);
+llvm::raw_ostream &debugFooter(unsigned width = 80);
 
 } // namespace circt
 

lib/Support/Debug.cpp

@@ -1,4 +1,4 @@
-//===- Debug.cpp - Debug Utilities ------------------------------*- C++ -*-===//
+//===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -11,39 +11,38 @@
 //===----------------------------------------------------------------------===//
 
 #include "circt/Support/Debug.h"
-
 #include "llvm/ADT/Twine.h"
 #include "llvm/Support/Debug.h"
 
-llvm::raw_ostream &circt::debugHeader(llvm::StringRef str, int width) {
-  auto &dbgStream = llvm::dbgs();
-  dbgStream << "===- " << str << " ";
-  width -= 6 + str.size();
-  if (width > 3) {
-    dbgStream << std::string(width - 3, '-');
-    width = 3;
+llvm::raw_ostream &circt::debugHeader(const llvm::Twine &str, unsigned width) {
+  auto &os = llvm::dbgs();
+  auto start = os.tell();
+  os << "===- " << str << " ";
+  auto endAct = os.tell() + 4; // 4 for "-==="
+  auto endExp = start + width;
+  while (endAct < endExp) {
+    os << '-';
+    ++endAct;
   }
-  if (width > 0)
-    dbgStream << std::string(width, '=');
-  return dbgStream;
+  os << "-===";
+  return os;
 }
 
-llvm::raw_ostream &circt::debugPassHeader(const mlir::Pass *pass, int width) {
-  return debugHeader((llvm::Twine("Running ") + pass->getName()).str());
+llvm::raw_ostream &circt::debugPassHeader(const mlir::Pass *pass,
+                                          unsigned width) {
+  return debugHeader(llvm::Twine("Running ") + pass->getName());
 }
 
-llvm::raw_ostream &circt::debugFooter(int width) {
-  auto &dbgStream = llvm::dbgs();
-  if (width > 3) {
-    int startWidth = std::min(width - 3, 3);
-    dbgStream << std::string(startWidth, '=');
-    width -= startWidth;
-  }
-  if (width > 3) {
-    dbgStream << std::string(width - 3, '-');
-    width = 3;
+llvm::raw_ostream &circt::debugFooter(unsigned width) {
+  auto &os = llvm::dbgs();
+  auto start = os.tell();
+  os << "===";
+  auto endAct = os.tell() + 3; // 3 for trailing "==="
+  auto endExp = start + width;
+  while (endAct < endExp) {
+    os << '-';
+    ++endAct;
   }
-  if (width > 0)
-    dbgStream << std::string(width, '=');
-  return dbgStream;
+  os << "===";
+  return os;
 }