Bug 1824772: part 1 - Add jit option and static pref to toggle eager baseline hints. r=iain

Add a pref, javascript.options.jitHints, to toggle eager baseline hints.

Differential Revision: https://phabricator.services.mozilla.com/D175521

js/src/jit/JitOptions.cpp

@@ -179,6 +179,9 @@ DefaultJitOptions::DefaultJitOptions() {
   // Duplicated in all.js - ensure both match.
   SET_DEFAULT(baselineJitWarmUpThreshold, 100);
 
+  // Disable eager baseline jit hints
+  SET_DEFAULT(disableJitHints, false);
+
   // How many invocations or loop iterations are needed before functions
   // are considered for trial inlining.
   SET_DEFAULT(trialInliningWarmUpThreshold, 500);

js/src/jit/JitOptions.h

@@ -45,6 +45,7 @@ struct DefaultJitOptions {
   bool checkRangeAnalysis;
   bool runExtraChecks;
   bool disableJitBackend;
+  bool disableJitHints;
   bool disableAma;
   bool disableEaa;
   bool disableEdgeCaseAnalysis;

js/src/jsapi.cpp

@@ -4183,6 +4183,9 @@ JS_PUBLIC_API void JS_SetGlobalJitCompilerOption(JSContext* cx,
     case JSJITCOMPILER_NATIVE_REGEXP_ENABLE:
       jit::JitOptions.nativeRegExp = !!value;
       break;
+    case JSJITCOMPILER_JIT_HINTS_ENABLE:
+      jit::JitOptions.disableJitHints = !value;
+      break;
     case JSJITCOMPILER_OFFTHREAD_COMPILATION_ENABLE:
       if (value == 1) {
         rt->setOffthreadIonCompilationEnabled(true);

js/src/jsapi.h

@@ -829,6 +829,7 @@ extern JS_PUBLIC_API void JS_SetOffthreadIonCompilationEnabled(JSContext* cx,
   Register(FULL_DEBUG_CHECKS, "jit.full-debug-checks") \
   Register(JUMP_THRESHOLD, "jump-threshold") \
   Register(NATIVE_REGEXP_ENABLE, "native_regexp.enable") \
+  Register(JIT_HINTS_ENABLE, "jitHints.enable") \
   Register(SIMULATOR_ALWAYS_INTERRUPT, "simulator.always-interrupt")      \
   Register(SPECTRE_INDEX_MASKING, "spectre.index-masking") \
   Register(SPECTRE_OBJECT_MITIGATIONS, "spectre.object-mitigations") \

js/src/shell/js.cpp

@@ -11555,6 +11555,8 @@ bool InitOptionParser(OptionParser& op) {
       !op.addBoolOption('\0', "blinterp",
                         "Enable Baseline Interpreter (default)") ||
       !op.addBoolOption('\0', "no-blinterp", "Disable Baseline Interpreter") ||
+      !op.addBoolOption('\0', "disable-jithints",
+                        "Disable caching eager baseline compilation hints.") ||
       !op.addBoolOption(
           '\0', "emit-interpreter-entry",
           "Emit Interpreter entry trampolines (default under --enable-perf)") ||
@@ -12349,6 +12351,10 @@ bool SetContextJITOptions(JSContext* cx, const OptionParser& op) {
     jit::JitOptions.baselineInterpreter = false;
   }
 
+  if (op.getBoolOption("disable-jithints")) {
+    jit::JitOptions.disableJitHints = true;
+  }
+
   if (op.getBoolOption("emit-interpreter-entry")) {
     jit::JitOptions.emitInterpreterEntryTrampoline = true;
   }

js/xpconnect/src/XPCJSContext.cpp

@@ -895,6 +895,7 @@ static void LoadStartupJSPrefs(XPCJSContext* xpccx) {
         cx, JSJITCOMPILER_JIT_TRUSTEDPRINCIPALS_ENABLE, false);
     JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_NATIVE_REGEXP_ENABLE,
                                   false);
+    JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_JIT_HINTS_ENABLE, false);
     sSelfHostedUseSharedMemory = false;
   } else {
     JS_SetGlobalJitCompilerOption(
@@ -909,6 +910,11 @@ static void LoadStartupJSPrefs(XPCJSContext* xpccx) {
     JS_SetGlobalJitCompilerOption(
         cx, JSJITCOMPILER_NATIVE_REGEXP_ENABLE,
         StaticPrefs::javascript_options_native_regexp_DoNotUseDirectly());
+    JS_SetGlobalJitCompilerOption(
+        cx, JSJITCOMPILER_JIT_HINTS_ENABLE,
+        XRE_IsContentProcess()
+            ? StaticPrefs::javascript_options_jitHints_DoNotUseDirectly()
+            : false);
     sSelfHostedUseSharedMemory = StaticPrefs::
         javascript_options_self_hosted_use_shared_memory_DoNotUseDirectly();
   }

modules/libpref/init/StaticPrefList.yaml

@@ -7470,6 +7470,14 @@
   mirror: always  # LoadStartupJSPrefs
   do_not_use_directly: true
 
+# Jit Hints Cache - An in-process cache to
+# accelerate repeated baseline compilations
+- name: javascript.options.jitHints
+  type: bool
+  value: true
+  mirror: always  # LoadStartupJSPrefs
+  do_not_use_directly: true
+
 # "Warm-up" thresholds at which we attempt to compile a script/function with
 # the next JIT tier.
 #