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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sts=4 et sw=4 tw=99:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#ifndef js_ProfilingStack_h
#define js_ProfilingStack_h
#include "jsbytecode.h"
#include "jstypes.h"
#include "js/TypeDecls.h"
#include "js/Utility.h"
struct JSRuntime;
namespace js {
// A call stack can be specified to the JS engine such that all JS entry/exits
// to functions push/pop an entry to/from the specified stack.
// For more detailed information, see vm/SPSProfiler.h.
class ProfileEntry
// All fields are marked volatile to prevent the compiler from re-ordering
// instructions. Namely this sequence:
// entry[size] = ...;
// size++;
// If the size modification were somehow reordered before the stores, then
// if a sample were taken it would be examining bogus information.
// A ProfileEntry represents both a C++ profile entry and a JS one.
// Descriptive string of this entry.
const char * volatile string;
// Stack pointer for non-JS entries, the script pointer otherwise.
void * volatile spOrScript;
// Line number for non-JS entries, the bytecode offset otherwise.
int32_t volatile lineOrPc;
// General purpose storage describing this frame.
uint32_t volatile flags_;
// These traits are bit masks. Make sure they're powers of 2.
enum Flags {
// Indicate whether a profile entry represents a CPP frame. If not set,
// a JS frame is assumed by default. You're not allowed to publicly
// change the frame type. Instead, initialize the ProfileEntry as either
// a JS or CPP frame with `initJsFrame` or `initCppFrame` respectively.
IS_CPP_ENTRY = 0x01,
// Indicate that copying the frame label is not necessary when taking a
// sample of the pseudostack.
// This ProfileEntry is a dummy entry indicating the start of a run
// of JS pseudostack entries.
// This flag is used to indicate that an interpreter JS entry has OSR-ed
// into baseline.
OSR = 0x08,
// Union of all flags.
// Mask for removing all flags except the category information.
// Keep these in sync with devtools/client/performance/modules/global.js
enum class Category : uint32_t {
OTHER = 0x10,
CSS = 0x20,
JS = 0x40,
GC = 0x80,
CC = 0x100,
NETWORK = 0x200,
GRAPHICS = 0x400,
STORAGE = 0x800,
EVENTS = 0x1000,
static_assert((static_cast<int>(Category::FIRST) & Flags::ALL) == 0,
"The category bitflags should not intersect with the other flags!");
// All of these methods are marked with the 'volatile' keyword because SPS's
// representation of the stack is stored such that all ProfileEntry
// instances are volatile. These methods would not be available unless they
// were marked as volatile as well.
bool isCpp() const volatile { return hasFlag(IS_CPP_ENTRY); }
bool isJs() const volatile { return !isCpp(); }
bool isCopyLabel() const volatile { return hasFlag(FRAME_LABEL_COPY); }
void setLabel(const char* aString) volatile { string = aString; }
const char* label() const volatile { return string; }
void initJsFrame(JSScript* aScript, jsbytecode* aPc) volatile {
flags_ = 0;
spOrScript = aScript;
void initCppFrame(void* aSp, uint32_t aLine) volatile {
flags_ = IS_CPP_ENTRY;
spOrScript = aSp;
lineOrPc = static_cast<int32_t>(aLine);
void setFlag(uint32_t flag) volatile {
flags_ |= flag;
void unsetFlag(uint32_t flag) volatile {
flags_ &= ~flag;
bool hasFlag(uint32_t flag) const volatile {
return bool(flags_ & flag);
uint32_t flags() const volatile {
return flags_;
uint32_t category() const volatile {
return flags_ & CATEGORY_MASK;
void setCategory(Category c) volatile {
MOZ_ASSERT(c >= Category::FIRST);
MOZ_ASSERT(c <= Category::LAST);
flags_ &= ~CATEGORY_MASK;
void setOSR() volatile {
void unsetOSR() volatile {
bool isOSR() const volatile {
return hasFlag(OSR);
void* stackAddress() const volatile {
return spOrScript;
JSScript* script() const volatile {
return (JSScript*)spOrScript;
uint32_t line() const volatile {
return static_cast<uint32_t>(lineOrPc);
// We can't know the layout of JSScript, so look in vm/SPSProfiler.cpp.
JS_FRIEND_API(jsbytecode*) pc() const volatile;
JS_FRIEND_API(void) setPC(jsbytecode* pc) volatile;
// The offset of a pc into a script's code can actually be 0, so to
// signify a nullptr pc, use a -1 index. This is checked against in
// pc() and setPC() to set/get the right pc.
static const int32_t NullPCOffset = -1;
static size_t offsetOfLabel() { return offsetof(ProfileEntry, string); }
static size_t offsetOfSpOrScript() { return offsetof(ProfileEntry, spOrScript); }
static size_t offsetOfLineOrPc() { return offsetof(ProfileEntry, lineOrPc); }
static size_t offsetOfFlags() { return offsetof(ProfileEntry, flags_); }
SetRuntimeProfilingStack(JSRuntime* rt, ProfileEntry* stack, uint32_t* size,
uint32_t max);
EnableRuntimeProfilingStack(JSRuntime* rt, bool enabled);
RegisterRuntimeProfilingEventMarker(JSRuntime* rt, void (*fn)(const char*));
ProfilingGetPC(JSRuntime* rt, JSScript* script, void* ip);
} // namespace js
#endif /* js_ProfilingStack_h */