[MLIR] Migrate pattern application / dialect conversion to the LDBG logging format

This prefix the output with the DEBUG_TYPE.
Dialect conversion is using a ScopedPrinter, we insert the raw_ldbg_ostream to
consistently prefix each new line.

Author: joker-eph

llvm/include/llvm/Support/DebugLog.h

@@ -61,8 +61,10 @@ namespace llvm {
   for (bool _c =                                                               \
            (::llvm::DebugFlag && ::llvm::isCurrentDebugType(TYPE, LEVEL));     \
        _c; _c = false)                                                         \
+    for (::llvm::impl::RAIINewLineStream NewLineStream{(STREAM)}; _c;          \
+         _c = false)                                                           \
   ::llvm::impl::raw_ldbg_ostream{                                              \
-      ::llvm::impl::computePrefix(TYPE, FILE, LINE, LEVEL), (STREAM)}          \
+      ::llvm::impl::computePrefix(TYPE, FILE, LINE, LEVEL), NewLineStream}     \
       .asLvalue()
 
 #define DEBUGLOG_WITH_STREAM_TYPE_AND_FILE(STREAM, LEVEL, TYPE, FILE)          \
@@ -81,14 +83,15 @@ namespace llvm {
 
 namespace impl {
 
-/// A raw_ostream that tracks `\n` and print the prefix.
+/// A raw_ostream that tracks `\n` and print the prefix after each
+/// newline.
 class LLVM_ABI raw_ldbg_ostream final : public raw_ostream {
   std::string Prefix;
   raw_ostream &Os;
-  bool HasPendingNewline = true;
+  bool HasPendingNewline;
 
-  /// Split the line on newlines and insert the prefix before each newline.
-  /// Forward everything to the underlying stream.
+  /// Split the line on newlines and insert the prefix before each
+  /// newline. Forward everything to the underlying stream.
   void write_impl(const char *Ptr, size_t Size) final {
     auto Str = StringRef(Ptr, Size);
     // Handle the initial prefix.
@@ -109,22 +112,18 @@ class LLVM_ABI raw_ldbg_ostream final : public raw_ostream {
   }
   void emitPrefix() { Os.write(Prefix.c_str(), Prefix.size()); }
   void writeWithPrefix(StringRef Str) {
-    if (HasPendingNewline) {
-      emitPrefix();
-      HasPendingNewline = false;
-    }
+    flushEol();
     Os.write(Str.data(), Str.size());
   }
 
 public:
-  explicit raw_ldbg_ostream(std::string Prefix, raw_ostream &Os)
-      : Prefix(std::move(Prefix)), Os(Os) {
+  explicit raw_ldbg_ostream(std::string Prefix, raw_ostream &Os,
+                            bool HasPendingNewline = true)
+      : Prefix(std::move(Prefix)), Os(Os),
+        HasPendingNewline(HasPendingNewline) {
     SetUnbuffered();
   }
-  ~raw_ldbg_ostream() final {
-    flushEol();
-    Os << '\n';
-  }
+  ~raw_ldbg_ostream() final { flushEol(); }
   void flushEol() {
     if (HasPendingNewline) {
       emitPrefix();
@@ -135,10 +134,22 @@ class LLVM_ABI raw_ldbg_ostream final : public raw_ostream {
   /// Forward the current_pos method to the underlying stream.
   uint64_t current_pos() const final { return Os.tell(); }
 
-  /// Some of the `<<` operators expect an lvalue, so we trick the type system.
+  /// Some of the `<<` operators expect an lvalue, so we trick the type
+  /// system.
   raw_ldbg_ostream &asLvalue() { return *this; }
 };
 
+/// A raw_ostream that prints a newline on destruction, useful for LDBG()
+class RAIINewLineStream final : public raw_ostream {
+  raw_ostream &Os;
+
+public:
+  RAIINewLineStream(raw_ostream &Os) : Os(Os) { SetUnbuffered(); }
+  ~RAIINewLineStream() { Os << '\n'; }
+  void write_impl(const char *Ptr, size_t Size) final { Os.write(Ptr, Size); }
+  uint64_t current_pos() const final { return Os.tell(); }
+};
+
 /// Remove the path prefix from the file name.
 static LLVM_ATTRIBUTE_UNUSED constexpr const char *
 getShortFileName(const char *path) {

llvm/unittests/Support/DebugLogTest.cpp

@@ -121,7 +121,7 @@ TEST(DebugLogTest, StreamPrefix) {
     EXPECT_EQ(os.str(), expected);
   }
   // After destructors, there was a pending newline for stream B.
-  EXPECT_EQ(os.str(), expected + "\nPrefixB \n");
+  EXPECT_EQ(os.str(), expected + "PrefixB ");
 }
 #else
 TEST(DebugLogTest, Basic) {

mlir/lib/Rewrite/PatternApplicator.cpp

@@ -13,7 +13,7 @@
 
 #include "mlir/Rewrite/PatternApplicator.h"
 #include "ByteCode.h"
-#include "llvm/Support/Debug.h"
+#include "llvm/Support/DebugLog.h"
 
 #ifndef NDEBUG
 #include "llvm/ADT/ScopeExit.h"
@@ -51,9 +51,7 @@ static Operation *getDumpRootOp(Operation *op) {
   return op;
 }
 static void logSucessfulPatternApplication(Operation *op) {
-  llvm::dbgs() << "// *** IR Dump After Pattern Application ***\n";
-  op->dump();
-  llvm::dbgs() << "\n\n";
+  LDBG(2) << "// *** IR Dump After Pattern Application ***\n" << *op << "\n";
 }
 #endif
 
@@ -208,8 +206,8 @@ LogicalResult PatternApplicator::matchAndRewrite(
             result =
                 bytecode->rewrite(rewriter, *pdlMatch, *mutableByteCodeState);
           } else {
-            LLVM_DEBUG(llvm::dbgs() << "Trying to match \""
-                                    << bestPattern->getDebugName() << "\"\n");
+            LDBG() << "Trying to match \"" << bestPattern->getDebugName()
+                   << "\"";
             const auto *pattern =
                 static_cast<const RewritePattern *>(bestPattern);
 
@@ -223,9 +221,8 @@ LogicalResult PatternApplicator::matchAndRewrite(
                 [&] { rewriter.setListener(oldListener); });
 #endif
             result = pattern->matchAndRewrite(op, rewriter);
-            LLVM_DEBUG(llvm::dbgs()
-                       << "\"" << bestPattern->getDebugName() << "\" result "
-                       << succeeded(result) << "\n");
+            LDBG() << " -> matchAndRewrite "
+                   << (succeeded(result) ? "successful" : "failed");
           }
 
           // Process the result of the pattern application.

mlir/lib/Transforms/Utils/DialectConversion.cpp

@@ -20,6 +20,7 @@
 #include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/DebugLog.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/SaveAndRestore.h"
 #include "llvm/Support/ScopedPrinter.h"
@@ -1129,8 +1130,13 @@ struct ConversionPatternRewriterImpl : public RewriterBase::Listener {
   /// verification.
   SmallPtrSet<Operation *, 1> pendingRootUpdates;
 
+  /// A raw output stream used to prefix the debug log.
+  llvm::impl::raw_ldbg_ostream os{(Twine("[") + DEBUG_TYPE + "] ").str(),
+                                  llvm::dbgs(), /*HasPendingNewline=*/false};
+
   /// A logger used to emit diagnostics during the conversion process.
-  llvm::ScopedPrinter logger{llvm::dbgs()};
+  llvm::ScopedPrinter logger{os};
+  std::string logPrefix;
 #endif
 };
 } // namespace detail