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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* 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
#ifndef vm_BytecodeUtil_h
#define vm_BytecodeUtil_h
/*
* JS bytecode definitions.
*/
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/EndianUtils.h"
#include <algorithm>
#include <stddef.h>
#include <stdint.h>
#include "jstypes.h"
#include "NamespaceImports.h"
#include "js/TypeDecls.h"
#include "js/Utility.h"
#include "js/Value.h"
#include "vm/BytecodeFormatFlags.h" // JOF_*
#include "vm/GeneratorResumeKind.h"
#include "vm/Opcodes.h"
#include "vm/SharedStencil.h" // js::GCThingIndex
#include "vm/ThrowMsgKind.h" // ThrowMsgKind, ThrowCondition
namespace js {
class JS_PUBLIC_API StringPrinter;
} // namespace js
/* Shorthand for type from format. */
static inline uint32_t JOF_TYPE(uint32_t fmt) { return fmt & JOF_TYPEMASK; }
/*
* Immediate operand getters, setters, and bounds.
*/
static MOZ_ALWAYS_INLINE uint8_t GET_UINT8(jsbytecode* pc) {
return uint8_t(pc[1]);
}
static MOZ_ALWAYS_INLINE void SET_UINT8(jsbytecode* pc, uint8_t u) {
pc[1] = jsbytecode(u);
}
/* Common uint16_t immediate format helpers. */
static inline jsbytecode UINT16_HI(uint16_t i) { return jsbytecode(i >> 8); }
static inline jsbytecode UINT16_LO(uint16_t i) { return jsbytecode(i); }
static MOZ_ALWAYS_INLINE uint16_t GET_UINT16(const jsbytecode* pc) {
uint16_t result;
mozilla::NativeEndian::copyAndSwapFromLittleEndian(&result, pc + 1, 1);
return result;
}
static MOZ_ALWAYS_INLINE void SET_UINT16(jsbytecode* pc, uint16_t i) {
mozilla::NativeEndian::copyAndSwapToLittleEndian(pc + 1, &i, 1);
}
static const unsigned UINT16_LIMIT = 1 << 16;
/* Helpers for accessing the offsets of jump opcodes. */
static const unsigned JUMP_OFFSET_LEN = 4;
static const int32_t JUMP_OFFSET_MIN = INT32_MIN;
static const int32_t JUMP_OFFSET_MAX = INT32_MAX;
static MOZ_ALWAYS_INLINE uint32_t GET_UINT24(const jsbytecode* pc) {
#if MOZ_LITTLE_ENDIAN()
// Do a single 32-bit load (for opcode and operand), then shift off the
// opcode.
uint32_t result;
memcpy(&result, pc, 4);
return result >> 8;
#else
return uint32_t((pc[3] << 16) | (pc[2] << 8) | pc[1]);
#endif
}
static MOZ_ALWAYS_INLINE void SET_UINT24(jsbytecode* pc, uint32_t i) {
MOZ_ASSERT(i < (1 << 24));
#if MOZ_LITTLE_ENDIAN()
memcpy(pc + 1, &i, 3);
#else
pc[1] = jsbytecode(i);
pc[2] = jsbytecode(i >> 8);
pc[3] = jsbytecode(i >> 16);
#endif
}
static MOZ_ALWAYS_INLINE int8_t GET_INT8(const jsbytecode* pc) {
return int8_t(pc[1]);
}
static MOZ_ALWAYS_INLINE uint32_t GET_UINT32(const jsbytecode* pc) {
uint32_t result;
mozilla::NativeEndian::copyAndSwapFromLittleEndian(&result, pc + 1, 1);
return result;
}
static MOZ_ALWAYS_INLINE void SET_UINT32(jsbytecode* pc, uint32_t u) {
mozilla::NativeEndian::copyAndSwapToLittleEndian(pc + 1, &u, 1);
}
static MOZ_ALWAYS_INLINE JS::Value GET_INLINE_VALUE(const jsbytecode* pc) {
uint64_t raw;
mozilla::NativeEndian::copyAndSwapFromLittleEndian(&raw, pc + 1, 1);
return JS::Value::fromRawBits(raw);
}
static MOZ_ALWAYS_INLINE void SET_INLINE_VALUE(jsbytecode* pc,
const JS::Value& v) {
uint64_t raw = v.asRawBits();
mozilla::NativeEndian::copyAndSwapToLittleEndian(pc + 1, &raw, 1);
}
static MOZ_ALWAYS_INLINE int32_t GET_INT32(const jsbytecode* pc) {
return static_cast<int32_t>(GET_UINT32(pc));
}
static MOZ_ALWAYS_INLINE void SET_INT32(jsbytecode* pc, int32_t i) {
SET_UINT32(pc, static_cast<uint32_t>(i));
}
static MOZ_ALWAYS_INLINE int32_t GET_JUMP_OFFSET(jsbytecode* pc) {
return GET_INT32(pc);
}
static MOZ_ALWAYS_INLINE void SET_JUMP_OFFSET(jsbytecode* pc, int32_t off) {
SET_INT32(pc, off);
}
static const unsigned GCTHING_INDEX_LEN = 4;
static MOZ_ALWAYS_INLINE js::GCThingIndex GET_GCTHING_INDEX(
const jsbytecode* pc) {
return js::GCThingIndex(GET_UINT32(pc));
}
static MOZ_ALWAYS_INLINE void SET_GCTHING_INDEX(jsbytecode* pc,
js::GCThingIndex index) {
SET_UINT32(pc, index.index);
}
// Index limit is determined by SrcNote::FourByteOffsetFlag, see
// frontend/BytecodeEmitter.h.
static const unsigned INDEX_LIMIT_LOG2 = 31;
static const uint32_t INDEX_LIMIT = uint32_t(1) << INDEX_LIMIT_LOG2;
static inline jsbytecode ARGC_HI(uint16_t argc) { return UINT16_HI(argc); }
static inline jsbytecode ARGC_LO(uint16_t argc) { return UINT16_LO(argc); }
static inline uint16_t GET_ARGC(const jsbytecode* pc) { return GET_UINT16(pc); }
static const unsigned ARGC_LIMIT = UINT16_LIMIT;
static inline uint16_t GET_ARGNO(const jsbytecode* pc) {
return GET_UINT16(pc);
}
static inline void SET_ARGNO(jsbytecode* pc, uint16_t argno) {
SET_UINT16(pc, argno);
}
static const unsigned ARGNO_LEN = 2;
static const unsigned ARGNO_LIMIT = UINT16_LIMIT;
static inline uint32_t GET_LOCALNO(const jsbytecode* pc) {
return GET_UINT24(pc);
}
static inline void SET_LOCALNO(jsbytecode* pc, uint32_t varno) {
SET_UINT24(pc, varno);
}
static const unsigned LOCALNO_LEN = 3;
static const unsigned LOCALNO_BITS = 24;
static const uint32_t LOCALNO_LIMIT = 1 << LOCALNO_BITS;
static inline uint32_t GET_RESUMEINDEX(const jsbytecode* pc) {
return GET_UINT24(pc);
}
static inline void SET_RESUMEINDEX(jsbytecode* pc, uint32_t resumeIndex) {
SET_UINT24(pc, resumeIndex);
}
static const unsigned ICINDEX_LEN = 4;
static inline uint32_t GET_ICINDEX(const jsbytecode* pc) {
return GET_UINT32(pc);
}
static inline void SET_ICINDEX(jsbytecode* pc, uint32_t icIndex) {
SET_UINT32(pc, icIndex);
}
static inline unsigned LoopHeadDepthHint(jsbytecode* pc) {
MOZ_ASSERT(JSOp(*pc) == JSOp::LoopHead);
return GET_UINT8(pc + 4);
}
static inline void SetLoopHeadDepthHint(jsbytecode* pc, unsigned loopDepth) {
MOZ_ASSERT(JSOp(*pc) == JSOp::LoopHead);
uint8_t data = std::min(loopDepth, unsigned(UINT8_MAX));
SET_UINT8(pc + 4, data);
}
static inline bool IsBackedgePC(jsbytecode* pc) {
switch (JSOp(*pc)) {
case JSOp::Goto:
case JSOp::JumpIfTrue:
return GET_JUMP_OFFSET(pc) < 0;
default:
return false;
}
}
static inline bool IsBackedgeForLoopHead(jsbytecode* pc, jsbytecode* loopHead) {
MOZ_ASSERT(JSOp(*loopHead) == JSOp::LoopHead);
return IsBackedgePC(pc) && pc + GET_JUMP_OFFSET(pc) == loopHead;
}
/*
* Describes the 'hops' component of a JOF_ENVCOORD opcode.
*
* Note: this component is only 8 bits wide, limiting the maximum number of
* scopes between a use and def to roughly 255. This is a pretty small limit but
* note that SpiderMonkey's recursive descent parser can only parse about this
* many functions before hitting the C-stack recursion limit so this shouldn't
* be a significant limitation in practice.
*/
static inline uint8_t GET_ENVCOORD_HOPS(jsbytecode* pc) {
return GET_UINT8(pc);
}
static inline void SET_ENVCOORD_HOPS(jsbytecode* pc, uint8_t hops) {
SET_UINT8(pc, hops);
}
static const unsigned ENVCOORD_HOPS_LEN = 1;
static const unsigned ENVCOORD_HOPS_BITS = 8;
static const unsigned ENVCOORD_HOPS_LIMIT = 1 << ENVCOORD_HOPS_BITS;
/* Describes the 'slot' component of a JOF_ENVCOORD opcode. */
static inline uint32_t GET_ENVCOORD_SLOT(const jsbytecode* pc) {
return GET_UINT24(pc);
}
static inline void SET_ENVCOORD_SLOT(jsbytecode* pc, uint32_t slot) {
SET_UINT24(pc, slot);
}
static const unsigned ENVCOORD_SLOT_LEN = 3;
static const unsigned ENVCOORD_SLOT_BITS = 24;
static const uint32_t ENVCOORD_SLOT_LIMIT = 1 << ENVCOORD_SLOT_BITS;
struct JSCodeSpec {
uint8_t length; /* length including opcode byte */
int8_t nuses; /* arity, -1 if variadic */
int8_t ndefs; /* number of stack results */
uint32_t format; /* immediate operand format */
};
namespace js {
extern const JSCodeSpec CodeSpecTable[];
inline const JSCodeSpec& CodeSpec(JSOp op) {
return CodeSpecTable[uint8_t(op)];
}
extern const char* const CodeNameTable[];
inline const char* CodeName(JSOp op) { return CodeNameTable[uint8_t(op)]; }
/* Shorthand for type from opcode. */
static inline uint32_t JOF_OPTYPE(JSOp op) {
return JOF_TYPE(CodeSpec(op).format);
}
static inline bool IsJumpOpcode(JSOp op) { return JOF_OPTYPE(op) == JOF_JUMP; }
static inline bool BytecodeFallsThrough(JSOp op) {
// Note:
// * JSOp::Yield/JSOp::Await is considered to fall through, like JSOp::Call.
switch (op) {
case JSOp::Goto:
case JSOp::Default:
case JSOp::Return:
case JSOp::RetRval:
case JSOp::FinalYieldRval:
case JSOp::Throw:
case JSOp::ThrowWithStack:
case JSOp::ThrowMsg:
case JSOp::ThrowSetConst:
case JSOp::TableSwitch:
return false;
default:
return true;
}
}
static inline bool BytecodeIsJumpTarget(JSOp op) {
switch (op) {
case JSOp::JumpTarget:
case JSOp::LoopHead:
case JSOp::AfterYield:
return true;
default:
return false;
}
}
// The JSOp argument is superflous, but we are using it to avoid a
MOZ_ALWAYS_INLINE unsigned StackUses(JSOp op, jsbytecode* pc) {
MOZ_ASSERT(op == JSOp(*pc));
int nuses = CodeSpec(op).nuses;
if (nuses >= 0) {
return nuses;
}
MOZ_ASSERT(nuses == -1);
switch (op) {
case JSOp::PopN:
return GET_UINT16(pc);
case JSOp::New:
case JSOp::NewContent:
case JSOp::SuperCall:
return 2 + GET_ARGC(pc) + 1;
default:
/* stack: fun, this, [argc arguments] */
MOZ_ASSERT(op == JSOp::Call || op == JSOp::CallContent ||
op == JSOp::CallIgnoresRv || op == JSOp::Eval ||
op == JSOp::CallIter || op == JSOp::CallContentIter ||
op == JSOp::StrictEval);
return 2 + GET_ARGC(pc);
}
}
MOZ_ALWAYS_INLINE unsigned StackDefs(JSOp op) {
int ndefs = CodeSpec(op).ndefs;
MOZ_ASSERT(ndefs >= 0);
return ndefs;
}
#if defined(DEBUG) || defined(JS_JITSPEW)
/*
* Given bytecode address pc in script's main program code, compute the operand
* stack depth just before (JSOp) *pc executes. If *pc is not reachable, return
* false.
*/
extern bool ReconstructStackDepth(JSContext* cx, JSScript* script,
jsbytecode* pc, uint32_t* depth,
bool* reachablePC);
#endif
} /* namespace js */
#define JSDVG_IGNORE_STACK 0
#define JSDVG_SEARCH_STACK 1
namespace js {
/*
* Find the source expression that resulted in v, and return a newly allocated
* C-string containing it. Fall back on v's string conversion (fallback) if we
* can't find the bytecode that generated and pushed v on the operand stack.
*
* Search the current stack frame if spindex is JSDVG_SEARCH_STACK. Don't
* look for v on the stack if spindex is JSDVG_IGNORE_STACK. Otherwise,
* spindex is the negative index of v, measured from cx->fp->sp, or from a
* lower frame's sp if cx->fp is native.
*
* The optional argument skipStackHits can be used to skip a hit in the stack
* frame. This can be useful in self-hosted code that wants to report value
* errors containing decompiled values that are useful for the user, instead of
* values used internally by the self-hosted code.
*
* The caller must call JS_free on the result after a successful call.
*/
UniqueChars DecompileValueGenerator(JSContext* cx, int spindex, HandleValue v,
HandleString fallback,
int skipStackHits = 0);
/*
* Decompile the formal argument at formalIndex in the nearest non-builtin
* stack frame, falling back with converting v to source.
*/
JSString* DecompileArgument(JSContext* cx, int formalIndex, HandleValue v);
static inline unsigned GetOpLength(JSOp op) {
MOZ_ASSERT(uint8_t(op) < JSOP_LIMIT);
MOZ_ASSERT(CodeSpec(op).length > 0);
return CodeSpec(op).length;
}
static inline unsigned GetBytecodeLength(const jsbytecode* pc) {
JSOp op = (JSOp)*pc;
return GetOpLength(op);
}
static inline bool BytecodeIsPopped(jsbytecode* pc) {
jsbytecode* next = pc + GetBytecodeLength(pc);
return JSOp(*next) == JSOp::Pop;
}
extern bool IsValidBytecodeOffset(JSContext* cx, JSScript* script,
size_t offset);
inline bool IsArgOp(JSOp op) { return JOF_OPTYPE(op) == JOF_QARG; }
inline bool IsLocalOp(JSOp op) { return JOF_OPTYPE(op) == JOF_LOCAL; }
inline bool IsAliasedVarOp(JSOp op) { return JOF_OPTYPE(op) == JOF_ENVCOORD; }
inline bool IsGlobalOp(JSOp op) { return CodeSpec(op).format & JOF_GNAME; }
inline bool IsPropertySetOp(JSOp op) {
return CodeSpec(op).format & JOF_PROPSET;
}
inline bool IsPropertyInitOp(JSOp op) {
return CodeSpec(op).format & JOF_PROPINIT;
}
inline bool IsLooseEqualityOp(JSOp op) {
return op == JSOp::Eq || op == JSOp::Ne;
}
inline bool IsStrictEqualityOp(JSOp op) {
return op == JSOp::StrictEq || op == JSOp::StrictNe;
}
inline bool IsEqualityOp(JSOp op) {
return IsLooseEqualityOp(op) || IsStrictEqualityOp(op);
}
inline bool IsRelationalOp(JSOp op) {
return op == JSOp::Lt || op == JSOp::Le || op == JSOp::Gt || op == JSOp::Ge;
}
inline bool IsCheckStrictOp(JSOp op) {
return CodeSpec(op).format & JOF_CHECKSTRICT;
}
#ifdef DEBUG
inline bool IsCheckSloppyOp(JSOp op) {
return CodeSpec(op).format & JOF_CHECKSLOPPY;
}
#endif
inline bool IsAtomOp(JSOp op) { return JOF_OPTYPE(op) == JOF_ATOM; }
inline bool IsGetPropOp(JSOp op) { return op == JSOp::GetProp; }
inline bool IsGetPropPC(const jsbytecode* pc) { return IsGetPropOp(JSOp(*pc)); }
inline bool IsHiddenInitOp(JSOp op) {
return op == JSOp::InitHiddenProp || op == JSOp::InitHiddenElem ||
op == JSOp::InitHiddenPropGetter || op == JSOp::InitHiddenElemGetter ||
op == JSOp::InitHiddenPropSetter || op == JSOp::InitHiddenElemSetter;
}
inline bool IsLockedInitOp(JSOp op) {
return op == JSOp::InitLockedProp || op == JSOp::InitLockedElem;
}
inline bool IsStrictSetPC(jsbytecode* pc) {
JSOp op = JSOp(*pc);
return op == JSOp::StrictSetProp || op == JSOp::StrictSetName ||
op == JSOp::StrictSetGName || op == JSOp::StrictSetElem;
}
inline bool IsSetPropOp(JSOp op) {
return op == JSOp::SetProp || op == JSOp::StrictSetProp ||
op == JSOp::SetName || op == JSOp::StrictSetName ||
op == JSOp::SetGName || op == JSOp::StrictSetGName;
}
inline bool IsSetPropPC(const jsbytecode* pc) { return IsSetPropOp(JSOp(*pc)); }
inline bool IsGetElemOp(JSOp op) { return op == JSOp::GetElem; }
inline bool IsGetElemPC(const jsbytecode* pc) { return IsGetElemOp(JSOp(*pc)); }
inline bool IsSetElemOp(JSOp op) {
return op == JSOp::SetElem || op == JSOp::StrictSetElem;
}
inline bool IsSetElemPC(const jsbytecode* pc) { return IsSetElemOp(JSOp(*pc)); }
inline bool IsInvokeOp(JSOp op) { return CodeSpec(op).format & JOF_INVOKE; }
inline bool IsInvokePC(jsbytecode* pc) { return IsInvokeOp(JSOp(*pc)); }
inline bool IsStrictEvalPC(jsbytecode* pc) {
JSOp op = JSOp(*pc);
return op == JSOp::StrictEval || op == JSOp::StrictSpreadEval;
}
inline bool IsConstructOp(JSOp op) {
return CodeSpec(op).format & JOF_CONSTRUCT;
}
inline bool IsConstructPC(const jsbytecode* pc) {
return IsConstructOp(JSOp(*pc));
}
inline bool IsSpreadOp(JSOp op) { return CodeSpec(op).format & JOF_SPREAD; }
inline bool IsSpreadPC(const jsbytecode* pc) { return IsSpreadOp(JSOp(*pc)); }
// Returns true if the specified opcode is for `typeof name` where `name` is
// single identifier.
inline bool IsTypeOfNameOp(JSOp op) {
return op == JSOp::Typeof || op == JSOp::TypeofEq;
}
inline bool OpUsesEnvironmentChain(JSOp op) {
return CodeSpec(op).format & JOF_USES_ENV;
}
static inline int32_t GetBytecodeInteger(jsbytecode* pc) {
switch (JSOp(*pc)) {
case JSOp::Zero:
return 0;
case JSOp::One:
return 1;
case JSOp::Uint16:
return GET_UINT16(pc);
case JSOp::Uint24:
return GET_UINT24(pc);
case JSOp::Int8:
return GET_INT8(pc);
case JSOp::Int32:
return GET_INT32(pc);
default:
MOZ_CRASH("Bad op");
}
}
inline bool BytecodeOpHasIC(JSOp op) { return CodeSpec(op).format & JOF_IC; }
inline void GetCheckPrivateFieldOperands(jsbytecode* pc,
ThrowCondition* throwCondition,
ThrowMsgKind* throwKind) {
static_assert(sizeof(ThrowCondition) == sizeof(uint8_t));
static_assert(sizeof(ThrowMsgKind) == sizeof(uint8_t));
MOZ_ASSERT(JSOp(*pc) == JSOp::CheckPrivateField);
uint8_t throwConditionByte = GET_UINT8(pc);
uint8_t throwKindByte = GET_UINT8(pc + 1);
*throwCondition = static_cast<ThrowCondition>(throwConditionByte);
*throwKind = static_cast<ThrowMsgKind>(throwKindByte);
MOZ_ASSERT(*throwCondition == ThrowCondition::ThrowHas ||
*throwCondition == ThrowCondition::ThrowHasNot ||
*throwCondition == ThrowCondition::OnlyCheckRhs);
MOZ_ASSERT(*throwKind == ThrowMsgKind::PrivateDoubleInit ||
*throwKind == ThrowMsgKind::PrivateBrandDoubleInit ||
*throwKind == ThrowMsgKind::MissingPrivateOnGet ||
*throwKind == ThrowMsgKind::MissingPrivateOnSet);
}
// Return true iff the combination of the ThrowCondition and hasOwn result
// will throw an exception.
static inline bool CheckPrivateFieldWillThrow(ThrowCondition condition,
bool hasOwn) {
if ((condition == ThrowCondition::ThrowHasNot && !hasOwn) ||
(condition == ThrowCondition::ThrowHas && hasOwn)) {
// Met a throw condition.
return true;
}
return false;
}
/*
* Counts accumulated for a single opcode in a script. The counts tracked vary
* between opcodes, and this structure ensures that counts are accessed in a
* coherent fashion.
*/
class PCCounts {
/*
* Offset of the pc inside the script. This fields is used to lookup opcode
* which have annotations.
*/
size_t pcOffset_;
/*
* Record the number of execution of one instruction, or the number of
* throws executed.
*/
uint64_t numExec_;
public:
explicit PCCounts(size_t off) : pcOffset_(off), numExec_(0) {}
size_t pcOffset() const { return pcOffset_; }
// Used for sorting and searching.
bool operator<(const PCCounts& rhs) const {
return pcOffset_ < rhs.pcOffset_;
}
uint64_t& numExec() { return numExec_; }
uint64_t numExec() const { return numExec_; }
static const char numExecName[];
};
static inline jsbytecode* GetNextPc(jsbytecode* pc) {
return pc + GetBytecodeLength(pc);
}
inline GeneratorResumeKind IntToResumeKind(int32_t value) {
MOZ_ASSERT(uint32_t(value) <= uint32_t(GeneratorResumeKind::Return));
return static_cast<GeneratorResumeKind>(value);
}
inline GeneratorResumeKind ResumeKindFromPC(jsbytecode* pc) {
MOZ_ASSERT(JSOp(*pc) == JSOp::ResumeKind);
return IntToResumeKind(GET_UINT8(pc));
}
#if defined(DEBUG) || defined(JS_JITSPEW)
enum class DisassembleSkeptically { No, Yes };
/*
* Disassemblers, for debugging only.
*/
[[nodiscard]] extern bool Disassemble(
JSContext* cx, JS::Handle<JSScript*> script, bool lines, StringPrinter* sp,
DisassembleSkeptically skeptically = DisassembleSkeptically::No);
unsigned Disassemble1(JSContext* cx, JS::Handle<JSScript*> script,
jsbytecode* pc, unsigned loc, bool lines,
StringPrinter* sp);
extern UniqueChars ToDisassemblySource(JSContext* cx, HandleValue v);
#endif
[[nodiscard]] extern bool DumpRealmPCCounts(JSContext* cx);
} // namespace js
#endif /* vm_BytecodeUtil_h */