From dd9776be63b6f67f051a7aa0e82d10ac1c9f2f79 Mon Sep 17 00:00:00 2001
From: Filip Niksic <fniksic@google.com>
Date: Mon, 3 Mar 2025 13:25:57 -0800
Subject: [PATCH] Replace C++20 branch predictor hints with C++17-compliant
 Abseil versions.

PiperOrigin-RevId: 733038863
---
 centipede/runner_interceptors.cc |  9 +++++----
 common/BUILD                     |  1 +
 common/CMakeLists.txt            |  1 +
 common/blob_file.cc              | 11 +++++------
 4 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/centipede/runner_interceptors.cc b/centipede/runner_interceptors.cc
index 5bb3622d..dfb5f3f6 100644
--- a/centipede/runner_interceptors.cc
+++ b/centipede/runner_interceptors.cc
@@ -21,6 +21,7 @@
 #include <cstring>
 
 #include "absl/base/nullability.h"
+#include "absl/base/optimization.h"
 #include "./centipede/runner.h"
 
 using centipede::tls;
@@ -143,7 +144,7 @@ static NO_SANITIZE int memcmp_fallback(const void *s1, const void *s2,
 extern "C" NO_SANITIZE int memcmp(const void *s1, const void *s2, size_t n) {
   const int result =
       memcmp_orig ? memcmp_orig(s1, s2, n) : memcmp_fallback(s1, s2, n);
-  if (!tls.started) [[unlikely]] {
+  if (ABSL_PREDICT_FALSE(!tls.started)) {
     return result;
   }
   tls.TraceMemCmp(reinterpret_cast<uintptr_t>(__builtin_return_address(0)),
@@ -167,7 +168,7 @@ extern "C" NO_SANITIZE int strcmp(const char *s1, const char *s2) {
       // Need to include one more byte than the shorter string length
       // when falling back to memcmp e.g. "foo" < "foobar".
       strcmp_orig ? strcmp_orig(s1, s2) : memcmp_fallback(s1, s2, len + 1);
-  if (!tls.started) [[unlikely]] {
+  if (ABSL_PREDICT_FALSE(!tls.started)) {
     return result;
   }
   // Pass `len` here to avoid storing the trailing '\0' in the dictionary.
@@ -190,7 +191,7 @@ extern "C" NO_SANITIZE int strncmp(const char *s1, const char *s2, size_t n) {
   if (n > len + 1) n = len + 1;
   const int result =
       strncmp_orig ? strncmp_orig(s1, s2, n) : memcmp_fallback(s1, s2, n);
-  if (!tls.started) [[unlikely]] {
+  if (ABSL_PREDICT_FALSE(!tls.started)) {
     return result;
   }
   // Pass `len` here to avoid storing the trailing '\0' in the dictionary.
@@ -206,7 +207,7 @@ extern "C" int pthread_create(absl::Nonnull<pthread_t *> thread,
                               absl::Nullable<const pthread_attr_t *> attr,
                               void *(*start_routine)(void *),
                               absl::Nullable<void *> arg) {
-  if (!tls.started) [[unlikely]] {
+  if (ABSL_PREDICT_FALSE(!tls.started)) {
     return REAL(pthread_create)(thread, attr, start_routine, arg);
   }
   // Wrap the arguments. Will be deleted in MyThreadStart.
diff --git a/common/BUILD b/common/BUILD
index e2d55d3f..56f57c49 100644
--- a/common/BUILD
+++ b/common/BUILD
@@ -62,6 +62,7 @@ cc_library(
         ":logging",
         ":remote_file",
         ":status_macros",
+        "@com_google_absl//absl/base:core_headers",
         "@com_google_absl//absl/base:nullability",
         "@com_google_absl//absl/log",
         "@com_google_absl//absl/log:check",
diff --git a/common/CMakeLists.txt b/common/CMakeLists.txt
index c7eed491..07b70297 100644
--- a/common/CMakeLists.txt
+++ b/common/CMakeLists.txt
@@ -51,6 +51,7 @@ fuzztest_cc_library(
     fuzztest::remote_file
     fuzztest::status_macros
     absl::check
+    absl::core_headers
     absl::log
     absl::nullability
     absl::status
diff --git a/common/blob_file.cc b/common/blob_file.cc
index 50110518..bdc8f2f3 100644
--- a/common/blob_file.cc
+++ b/common/blob_file.cc
@@ -26,6 +26,7 @@
 #include <vector>
 
 #include "absl/base/nullability.h"
+#include "absl/base/optimization.h"
 #include "absl/log/check.h"
 #include "absl/log/log.h"
 #include "absl/status/status.h"
@@ -179,11 +180,11 @@ class DefaultBlobFileReader : public BlobFileReader {
     ASSIGN_OR_RETURN_IF_NOT_OK(std::unique_ptr<riegeli::Reader> new_reader,
                                CreateRiegeliFileReader(path));
     riegeli_reader_.Reset(std::move(new_reader));
-    if (riegeli_reader_.CheckFileFormat()) [[likely]] {
+    if (ABSL_PREDICT_TRUE(riegeli_reader_.CheckFileFormat())) {
       // File could be opened and is in the Riegeli format.
       return absl::OkStatus();
     }
-    if (!riegeli_reader_.src()->ok()) [[unlikely]] {
+    if (ABSL_PREDICT_FALSE(!riegeli_reader_.src()->ok())) {
       // File could not be opened.
       return riegeli_reader_.src()->status();
     }
@@ -210,8 +211,7 @@ class DefaultBlobFileReader : public BlobFileReader {
     else
       return absl::FailedPreconditionError("no reader open");
 #else
-    if (legacy_reader_) [[unlikely]]
-      return legacy_reader_->Read(blob);
+    if (ABSL_PREDICT_FALSE(legacy_reader_)) return legacy_reader_->Read(blob);
 
     absl::string_view record;
     if (!riegeli_reader_.ReadRecord(record)) {
@@ -230,8 +230,7 @@ class DefaultBlobFileReader : public BlobFileReader {
     legacy_reader_ = nullptr;
     return absl::OkStatus();
 #else
-    // NOLINTNEXTLINE(readability/braces). Similar to b/278586863.
-    if (legacy_reader_) [[unlikely]] {
+    if (ABSL_PREDICT_FALSE(legacy_reader_)) {
       legacy_reader_ = nullptr;
       return absl::OkStatus();
     }