[PGO] Allow collecting other kinds of pgo profiles.

https://bugs.webkit.org/show_bug.cgi?id=239776

Reviewed by Saam Barati.

Update the way we collect PGO profiles to use LLVM's file handling, because
it really seems to care about that. This allowws us to try out other kinds
of profile generation, like the IR-based -fcs-profile-generate.

* Source/WTF/wtf/GenerateProfiles.h:
(WTF::registerProfileGenerationCallback):

Canonical link: https://commits.webkit.org/250064@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@293544 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/WTF/ChangeLog

@@ -1,3 +1,17 @@
+2022-04-26  Justin Michaud  <justin_michaud@apple.com>
+
+        [PGO] Allow collecting other kinds of pgo profiles
+        https://bugs.webkit.org/show_bug.cgi?id=239776
+
+        Reviewed by Saam Barati.
+
+        Update the way we collect PGO profiles to use LLVM's file handling, because
+        it really seems to care about that. This allowws us to try out other kinds
+        of profile generation, like the IR-based -fcs-profile-generate.
+
+        * wtf/GenerateProfiles.h:
+        (WTF::registerProfileGenerationCallback):
+
 2022-04-27  Diego Pino Garcia  <dpino@igalia.com>
 
         [GCC] GCC9.3 defines 'remove_cvref_t' but not '__cpp_lib_remove_cvref'

Source/WTF/wtf/GenerateProfiles.h

@@ -32,8 +32,8 @@
 #include <notify.h>
 #include <unistd.h>
 
-extern "C" uint64_t __llvm_profile_get_size_for_buffer();
-extern "C" int __llvm_profile_write_buffer(char *);
+extern "C" int __llvm_profile_write_file(void);
+extern "C" void __llvm_profile_set_filename(const char*);
 extern "C" void __llvm_profile_reset_counters(void);
 
 #endif
@@ -44,37 +44,48 @@ template<typename OnceFlagDiversifier>
 ALWAYS_INLINE void registerProfileGenerationCallback(const char* name)
 {
 #if ENABLE(LLVM_PROFILE_GENERATION)
+    constexpr int WRITE_SUCCESS = 0;
+
+    static int profileCount = 0;
+    static NeverDestroyed<String> profileFileBase;
+    static NeverDestroyed<String> profileFileName;
     static std::once_flag registerFlag;
     std::call_once(registerFlag, [name] {
-        WTFLogAlways("<WEBKIT_LLVM_PROFILE><%s><%d><0>: Registering callback for profile data.", name, getpid());
+        int pid = getpid();
+        WTFLogAlways("<WEBKIT_LLVM_PROFILE><%s><%d>: Registering callback for profile data.", name, pid);
         WTFLogAlways("<WEBKIT_LLVM_PROFILE> To collect a profile: `notifyutil -p com.apple.WebKit.profiledata`");
         WTFLogAlways("<WEBKIT_LLVM_PROFILE> To copy the output: `"
             R"HERE(log stream --style json --color none | perl -mFile::Basename -mFile::Copy -nle 'if (m/<WEBKIT_LLVM_PROFILE>.*<BEGIN>(.*)<END>/) { (my $l = $1) =~ s/\\\//\//g; my $b = File::Basename::basename($l); my $d = "./profiles/$b"; print "Moving $l to $d"; File::Copy::move($l, $d); }')HERE"
             "`.");
         WTFLogAlways("<WEBKIT_LLVM_PROFILE> To sanity-check the output: `for f in ./profiles/*; do echo $f; xcrun -sdk macosx.internal llvm-profdata show $f; done;`.");
-        int token;
-        notify_register_dispatch("com.apple.WebKit.profiledata", &token, dispatch_get_main_queue(), ^(int) {
-            int pid = getpid();
-            int64_t time = MonotonicTime::now().secondsSinceEpoch().milliseconds();
 
-            auto bufferSize = __llvm_profile_get_size_for_buffer();
-            WTFLogAlways("<WEBKIT_LLVM_PROFILE><%s><%d><%lld>: LLVM collected %llu bytes of profile data.", 
-                name, pid, time, bufferSize);
+        {
+            // Maybe we could use %t instead here, but this folder is permitted through the sandbox because of ANGLE.
+            FileSystem::PlatformFileHandle fileHandle;
+            auto filePath = FileSystem::openTemporaryFile(makeString(name, "-", getpid()), fileHandle, ".profraw");
+            profileFileBase.get() = String::fromUTF8(filePath.utf8().data());
+            FileSystem::closeFile(fileHandle);
+        }
 
-            auto* buffer = static_cast<char*>(calloc(sizeof(char), bufferSize));
-            __llvm_profile_write_buffer(buffer);
+        WTFLogAlways("<WEBKIT_LLVM_PROFILE><%s><%d>: We will dump the resulting profile to %s.", name, pid, profileFileBase->utf8().data());
 
-            String fileName(String::fromUTF8(name) + "-" + pid + "-" + time + "-");
+        int token;
+        notify_register_dispatch("com.apple.WebKit.profiledata", &token, dispatch_get_main_queue(), ^(int) {
+            profileFileName.get() = makeString(profileFileBase.get(), ".", profileCount++, ".profraw");
+            __llvm_profile_set_filename(profileFileName->utf8().data()); // Must stay alive while it is used by llvm.
 
-            FileSystem::PlatformFileHandle fileHandle;
-            auto filePath = FileSystem::openTemporaryFile(fileName, fileHandle, ".profraw");
-            size_t bytesWritten = FileSystem::writeToFile(fileHandle, reinterpret_cast<const void*>(buffer), bufferSize);
+            WTFLogAlways("<WEBKIT_LLVM_PROFILE><%s><%d><%lf>: About to write to %s.", 
+                name, pid, MonotonicTime::now().secondsSinceEpoch().milliseconds(), profileFileName->utf8().data());
 
-            WTFLogAlways("<WEBKIT_LLVM_PROFILE><%s><%d><%lld>: Wrote %zu bytes to file <BEGIN>%s<END>.", 
-                name, pid, time, bytesWritten, filePath.utf8().data());
+            int writeResult = __llvm_profile_write_file();
+            if (writeResult == WRITE_SUCCESS) {
+                WTFLogAlways("<WEBKIT_LLVM_PROFILE><%s><%d><%lf>: Wrote to file <BEGIN>%s<END>.", 
+                    name, pid, MonotonicTime::now().secondsSinceEpoch().milliseconds(), profileFileName->utf8().data());
+            } else {
+                WTFLogAlways("<WEBKIT_LLVM_PROFILE><%s><%d><%lf>: Error writing profile file %s.", 
+                    name, pid, MonotonicTime::now().secondsSinceEpoch().milliseconds(), profileFileName->utf8().data());
+            }
 
-            FileSystem::closeFile(fileHandle);
-            free(buffer);
             __llvm_profile_reset_counters();
         });
     });