[llvm] Implement a custom stream for LDBG macro to handle newlines (PR #150750)
Mehdi Amini via llvm-commits
llvm-commits at lists.llvm.org
Sun Jul 27 13:15:27 PDT 2025
https://github.com/joker-eph updated https://github.com/llvm/llvm-project/pull/150750
>From 213d1b60e66b242e535f55c458746987d79d6d2f Mon Sep 17 00:00:00 2001
From: Mehdi Amini <joker.eph at gmail.com>
Date: Sat, 26 Jul 2025 03:51:17 -0700
Subject: [PATCH] Implement a custom stream for LDBG macro to handle newlines
This prints the prefix on every new line, allowing for an output that looks like:
[dead-code-analysis] DeadCodeAnalysis.cpp:284 Visiting program point: 0x55ea5be2d4c8 <after operation>:func.func private @private_1() -> (i32, i32) {...}
[dead-code-analysis] DeadCodeAnalysis.cpp:288 Visiting operation: func.func private @private_1() -> (i32, i32) {
[dead-code-analysis] DeadCodeAnalysis.cpp:288 %c0_i32 = arith.constant 0 : i32
[dead-code-analysis] DeadCodeAnalysis.cpp:288 %0 = arith.addi %c0_i32, %c0_i32 {tag = "one"} : i32
[dead-code-analysis] DeadCodeAnalysis.cpp:288 return %c0_i32, %0 : i32, i32
[dead-code-analysis] DeadCodeAnalysis.cpp:288 }
[dead-code-analysis] DeadCodeAnalysis.cpp:313 Visiting callable operation: func.func private @private_1() -> (i32, i32) {
[dead-code-analysis] DeadCodeAnalysis.cpp:313 %c0_i32 = arith.constant 0 : i32
[dead-code-analysis] DeadCodeAnalysis.cpp:313 %0 = arith.addi %c0_i32, %c0_i32 {tag = "one"} : i32
[dead-code-analysis] DeadCodeAnalysis.cpp:313 return %c0_i32, %0 : i32, i32
[dead-code-analysis] DeadCodeAnalysis.cpp:313 }
---
llvm/include/llvm/Support/DebugLog.h | 122 +++++++++++++++++-------
llvm/unittests/Support/DebugLogTest.cpp | 21 ++++
2 files changed, 108 insertions(+), 35 deletions(-)
diff --git a/llvm/include/llvm/Support/DebugLog.h b/llvm/include/llvm/Support/DebugLog.h
index b1b17e3ede950..3d326d773d1a1 100644
--- a/llvm/include/llvm/Support/DebugLog.h
+++ b/llvm/include/llvm/Support/DebugLog.h
@@ -26,55 +26,107 @@ namespace llvm {
// << "] " << "Bitset contains: " << Bitset << "\n");
#define LDBG() DEBUGLOG_WITH_STREAM_AND_TYPE(llvm::dbgs(), DEBUG_TYPE)
-#if defined(__SHORT_FILE__)
-#define DEBUGLOG_WITH_STREAM_AND_TYPE(STREAM, TYPE) \
+#define DEBUGLOG_WITH_STREAM_TYPE_AND_FILE(STREAM, TYPE, FILE) \
for (bool _c = (::llvm::DebugFlag && ::llvm::isCurrentDebugType(TYPE)); _c; \
_c = false) \
- ::llvm::impl::LogWithNewline(TYPE, __SHORT_FILE__, __LINE__, (STREAM))
+ ::llvm::impl::raw_ldbg_ostream { \
+ ::llvm::impl::computePrefix(TYPE, FILE, __LINE__), (STREAM) \
+ }
+// When __SHORT_FILE__ is not define, the File is the full path,
+// otherwise __SHORT_FILE__ is defined in CMake to provide the file name
+// without the path prefix.
+#if defined(__SHORT_FILE__)
+#define DEBUGLOG_WITH_STREAM_AND_TYPE(STREAM, TYPE) \
+ DEBUGLOG_WITH_STREAM_TYPE_AND_FILE(STREAM, TYPE, __SHORT_FILE__)
#else
#define DEBUGLOG_WITH_STREAM_AND_TYPE(STREAM, TYPE) \
- for (bool _c = (::llvm::DebugFlag && ::llvm::isCurrentDebugType(TYPE)); _c; \
- _c = false) \
- ::llvm::impl::LogWithNewline(TYPE, __FILE__, __LINE__, (STREAM))
+ DEBUGLOG_WITH_STREAM_TYPE_AND _FILE( \
+ STREAM, TYPE, ::llvm::impl::LogWithNewline::getShortFileName(__FILE__))
#endif
namespace impl {
-class LogWithNewline {
+
+/// A raw_ostream that tracks `\n` and print the prefix.
+class LLVM_ABI raw_ldbg_ostream final : public raw_ostream {
+ std::string Prefix;
+ raw_ostream &Os;
+ bool HasPendingNewline = true;
+
+ /// 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);
+ if (!Str.empty()) {
+ if (HasPendingNewline) {
+ emitPrefix();
+ HasPendingNewline = false;
+ }
+ }
+ auto Eol = Str.find('\n');
+ while (Eol != StringRef::npos) {
+ StringRef Line = Str.take_front(Eol + 1);
+ if (!Line.empty()) {
+ if (HasPendingNewline) {
+ emitPrefix();
+ HasPendingNewline = false;
+ }
+ Os.write(Line.data(), Line.size());
+ }
+ HasPendingNewline = true;
+ Str = Str.drop_front(Eol + 1);
+ Eol = Str.find('\n');
+ }
+ if (!Str.empty()) {
+ if (HasPendingNewline) {
+ emitPrefix();
+ HasPendingNewline = false;
+ }
+ Os.write(Str.data(), Str.size());
+ }
+ }
+ void emitPrefix() { Os.write(Prefix.c_str(), Prefix.size()); }
+
public:
- LogWithNewline(const char *debug_type, const char *file, int line,
- raw_ostream &os)
- : os(os) {
-#if !defined(__SHORT_FILE__)
- file = ::llvm::impl::LogWithNewline::getShortFileName(file);
-#endif
- if (debug_type)
- os << "[" << debug_type << "] ";
- os << file << ":" << line << " ";
+ explicit raw_ldbg_ostream(std::string Prefix, raw_ostream &Os)
+ : Prefix(std::move(Prefix)), Os(Os) {
+ SetUnbuffered();
}
- ~LogWithNewline() { os << '\n'; }
- template <typename T> raw_ostream &operator<<(const T &t) && {
- return os << t;
+ ~raw_ldbg_ostream() final {
+ flushEol();
+ Os << '\n';
}
-
- // Prevent copying, as this class manages newline responsibility and is
- // intended for use as a temporary.
- LogWithNewline(const LogWithNewline &) = delete;
- LogWithNewline &operator=(const LogWithNewline &) = delete;
- LogWithNewline &operator=(LogWithNewline &&) = delete;
- static constexpr const char *getShortFileName(const char *path) {
- // Remove the path prefix from the file name.
- const char *filename = path;
- for (const char *p = path; *p != '\0'; ++p) {
- if (*p == '/' || *p == '\\') {
- filename = p + 1;
- }
+ void flushEol() {
+ if (HasPendingNewline) {
+ emitPrefix();
+ HasPendingNewline = false;
}
- return filename;
}
-private:
- raw_ostream &os;
+ /// Forward the current_pos method to the underlying stream.
+ uint64_t current_pos() const final { return Os.tell(); }
};
+
+/// Remove the path prefix from the file name.
+static constexpr const char *getShortFileName(const char *path) {
+ for (const char *p = path; *p != '\0'; ++p) {
+ if (*p == '/' || *p == '\\')
+ path = p + 1;
+ }
+ return path;
+}
+
+/// Compute the prefix for the debug log in the form of:
+/// "[DebugType] File:Line "
+/// Where the File is the file name without the path prefix.
+static std::string computePrefix(const char *DebugType, const char *File,
+ int Line) {
+ std::string Prefix;
+ raw_string_ostream OsPrefix(Prefix);
+ if (DebugType)
+ OsPrefix << "[" << DebugType << "] ";
+ OsPrefix << File << ":" << Line << " ";
+ return OsPrefix.str();
+}
} // end namespace impl
#else
// As others in Debug, When compiling without assertions, the -debug-* options
diff --git a/llvm/unittests/Support/DebugLogTest.cpp b/llvm/unittests/Support/DebugLogTest.cpp
index b26fa40cc8687..b594a97d11e45 100644
--- a/llvm/unittests/Support/DebugLogTest.cpp
+++ b/llvm/unittests/Support/DebugLogTest.cpp
@@ -62,6 +62,27 @@ TEST(DebugLogTest, Basic) {
EXPECT_THAT(count, Eq(1));
}
}
+
+TEST(DebugLogTest, StreamPrefix) {
+ llvm::DebugFlag = true;
+ static const char *DT[] = {"A", "B"};
+ setCurrentDebugTypes(DT, 2);
+
+ std::string str;
+ raw_string_ostream os(str);
+ std::string expected = "PrefixA 1\nPrefixA 2\nPrefixB "
+ "3\nPrefixB 4\nPrefixA 5";
+ {
+ llvm::impl::raw_ldbg_ostream ldbg_osB("PrefixB ", os);
+ llvm::impl::raw_ldbg_ostream ldbg_osA("PrefixA ", os);
+ ldbg_osA << "1\n2\n";
+ ldbg_osB << "3\n4\n";
+ ldbg_osA << "5";
+ EXPECT_EQ(os.str(), expected);
+ }
+ // After destructors, there was a pending newline for stream B.
+ EXPECT_EQ(os.str(), expected + "\nPrefixB \n");
+}
#else
TEST(DebugLogTest, Basic) {
// LDBG should be compiled out in NDEBUG, so just check it compiles and has
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