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gecko/js/src/jsanalyze.cpp

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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 http://mozilla.org/MPL/2.0/. */
#include "jsanalyze.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/PodOperations.h"
#include "jsautooplen.h"
#include "jscompartment.h"
#include "jscntxt.h"
#include "jsinferinlines.h"
using namespace js;
using namespace js::analyze;
using mozilla::DebugOnly;
using mozilla::PodCopy;
using mozilla::PodZero;
/////////////////////////////////////////////////////////////////////
// Bytecode
/////////////////////////////////////////////////////////////////////
#ifdef DEBUG
void
analyze::PrintBytecode(JSContext *cx, HandleScript script, jsbytecode *pc)
{
printf("#%u:", script->id());
Sprinter sprinter(cx);
if (!sprinter.init())
return;
js_Disassemble1(cx, script, pc, pc - script->code, true, &sprinter);
fprintf(stdout, "%s", sprinter.string());
}
#endif
/////////////////////////////////////////////////////////////////////
// Bytecode Analysis
/////////////////////////////////////////////////////////////////////
inline bool
ScriptAnalysis::addJump(JSContext *cx, unsigned offset,
unsigned *currentOffset, unsigned *forwardJump, unsigned *forwardLoop,
unsigned stackDepth)
{
JS_ASSERT(offset < script_->length);
Bytecode *&code = codeArray[offset];
if (!code) {
code = cx->analysisLifoAlloc().new_<Bytecode>();
if (!code) {
setOOM(cx);
return false;
}
code->stackDepth = stackDepth;
}
JS_ASSERT(code->stackDepth == stackDepth);
code->jumpTarget = true;
if (offset < *currentOffset) {
/* Scripts containing loops are never inlined. */
isJaegerInlineable = false;
hasLoops_ = true;
if (code->analyzed) {
/*
* Backedge in a do-while loop, the body has been analyzed. Rewalk
* the body to set inLoop bits.
*/
for (unsigned i = offset; i <= *currentOffset; i++) {
Bytecode *code = maybeCode(i);
if (code)
code->inLoop = true;
}
} else {
/*
* Backedge in a while/for loop, whose body has not been analyzed
* due to a lack of fallthrough at the loop head. Roll back the
* offset to analyze the body.
*/
if (*forwardJump == 0)
*forwardJump = *currentOffset;
if (*forwardLoop == 0)
*forwardLoop = *currentOffset;
*currentOffset = offset;
}
} else if (offset > *forwardJump) {
*forwardJump = offset;
}
return true;
}
void
ScriptAnalysis::analyzeBytecode(JSContext *cx)
{
JS_ASSERT(cx->compartment->activeAnalysis);
JS_ASSERT(!ranBytecode());
LifoAlloc &alloc = cx->analysisLifoAlloc();
numSlots = TotalSlots(script_);
unsigned length = script_->length;
codeArray = alloc.newArray<Bytecode*>(length);
escapedSlots = alloc.newArray<bool>(numSlots);
if (!codeArray || !escapedSlots) {
setOOM(cx);
return;
}
PodZero(codeArray, length);
/*
* Populate arg and local slots which can escape and be accessed in ways
* other than through ARG* and LOCAL* opcodes (though arguments can still
* be indirectly read but not written through 'arguments' properties).
* All escaping locals are treated as having possible use-before-defs.
* Conservatively use 'argumentsHasVarBinding' instead of 'needsArgsObj'
* (needsArgsObj requires SSA which requires escapedSlots). Lastly, the
* debugger can access any local at any time. Even though debugger
* reads/writes are monitored by the DebugScopeProxy, this monitoring
* updates the flow-insensitive type sets, so we cannot use SSA.
*/
PodZero(escapedSlots, numSlots);
bool allVarsAliased = script_->compartment()->debugMode();
bool allArgsAliased = allVarsAliased || script_->argumentsHasVarBinding();
RootedScript script(cx, script_);
for (BindingIter bi(script); bi; bi++) {
if (bi->kind() == ARGUMENT)
escapedSlots[ArgSlot(bi.frameIndex())] = allArgsAliased || bi->aliased();
else
escapedSlots[LocalSlot(script_, bi.frameIndex())] = allVarsAliased || bi->aliased();
}
/*
* If the script is in debug mode, JS_SetFrameReturnValue can be called at
* any safe point.
*/
if (cx->compartment->debugMode())
usesReturnValue_ = true;
bool heavyweight = script_->function() && script_->function()->isHeavyweight();
isJaegerCompileable = true;
isJaegerInlineable = isIonInlineable = true;
if (heavyweight || cx->compartment->debugMode())
isJaegerInlineable = isIonInlineable = false;
if (script_->argumentsHasVarBinding())
isJaegerInlineable = false;
modifiesArguments_ = false;
if (heavyweight)
modifiesArguments_ = true;
canTrackVars = true;
/*
* If we are in the middle of one or more jumps, the offset of the highest
* target jumping over this bytecode. Includes implicit jumps from
* try/catch/finally blocks.
*/
unsigned forwardJump = 0;
/* If we are in the middle of a loop, the offset of the highest backedge. */
unsigned forwardLoop = 0;
/*
* If we are in the middle of a try block, the offset of the highest
* catch/finally/enditer.
*/
unsigned forwardCatch = 0;
/* Fill in stack depth and definitions at initial bytecode. */
Bytecode *startcode = alloc.new_<Bytecode>();
if (!startcode) {
setOOM(cx);
return;
}
startcode->stackDepth = 0;
codeArray[0] = startcode;
unsigned offset, nextOffset = 0;
while (nextOffset < length) {
offset = nextOffset;
JS_ASSERT(forwardCatch <= forwardJump);
/* Check if the current forward jump/try-block has finished. */
if (forwardJump && forwardJump == offset)
forwardJump = 0;
if (forwardCatch && forwardCatch == offset)
forwardCatch = 0;
Bytecode *code = maybeCode(offset);
jsbytecode *pc = script_->code + offset;
JSOp op = (JSOp)*pc;
JS_ASSERT(op < JSOP_LIMIT);
/* Immediate successor of this bytecode. */
unsigned successorOffset = offset + GetBytecodeLength(pc);
/*
* Next bytecode to analyze. This is either the successor, or is an
* earlier bytecode if this bytecode has a loop backedge.
*/
nextOffset = successorOffset;
if (!code) {
/* Haven't found a path by which this bytecode is reachable. */
continue;
}
/*
* Update info about bytecodes inside loops, which may have been
* analyzed before the backedge was seen.
*/
if (forwardLoop) {
code->inLoop = true;
if (forwardLoop <= offset)
forwardLoop = 0;
}
if (code->analyzed) {
/* No need to reanalyze, see Bytecode::mergeDefines. */
continue;
}
code->analyzed = true;
if (forwardCatch)
code->inTryBlock = true;
if (script_->hasBreakpointsAt(pc)) {
code->safePoint = true;
canTrackVars = false;
isJaegerInlineable = isIonInlineable = false;
}
unsigned stackDepth = code->stackDepth;
if (!forwardJump)
code->unconditional = true;
unsigned nuses = GetUseCount(script_, offset);
unsigned ndefs = GetDefCount(script_, offset);
JS_ASSERT(stackDepth >= nuses);
stackDepth -= nuses;
stackDepth += ndefs;
switch (op) {
case JSOP_RETURN:
case JSOP_STOP:
numReturnSites_++;
break;
case JSOP_SETRVAL:
case JSOP_POPV:
usesReturnValue_ = true;
isJaegerInlineable = isIonInlineable = false;
break;
case JSOP_NAME:
case JSOP_CALLNAME:
case JSOP_BINDNAME:
case JSOP_SETNAME:
case JSOP_DELNAME:
case JSOP_GETALIASEDVAR:
case JSOP_CALLALIASEDVAR:
case JSOP_SETALIASEDVAR:
case JSOP_LAMBDA:
usesScopeChain_ = true;
isJaegerInlineable = isIonInlineable = false;
break;
case JSOP_DEFFUN:
case JSOP_DEFVAR:
case JSOP_DEFCONST:
case JSOP_SETCONST:
usesScopeChain_ = true; // Requires access to VarObj via ScopeChain.
canTrackVars = false;
isJaegerInlineable = isIonInlineable = false;
break;
case JSOP_EVAL:
canTrackVars = false;
isJaegerInlineable = isIonInlineable = false;
break;
case JSOP_ENTERWITH:
isJaegerCompileable = canTrackVars = false;
isJaegerInlineable = isIonInlineable = false;
break;
case JSOP_ENTERLET0:
case JSOP_ENTERLET1:
case JSOP_ENTERBLOCK:
case JSOP_LEAVEBLOCK:
isJaegerInlineable = isIonInlineable = false;
break;
case JSOP_THIS:
usesThisValue_ = true;
break;
case JSOP_CALL:
case JSOP_NEW:
/* Only consider potentially inlineable calls here. */
hasFunctionCalls_ = true;
break;
case JSOP_TABLESWITCH: {
isJaegerInlineable = isIonInlineable = false;
unsigned defaultOffset = offset + GET_JUMP_OFFSET(pc);
jsbytecode *pc2 = pc + JUMP_OFFSET_LEN;
int32_t low = GET_JUMP_OFFSET(pc2);
pc2 += JUMP_OFFSET_LEN;
int32_t high = GET_JUMP_OFFSET(pc2);
pc2 += JUMP_OFFSET_LEN;
if (!addJump(cx, defaultOffset, &nextOffset, &forwardJump, &forwardLoop, stackDepth))
return;
getCode(defaultOffset).safePoint = true;
for (int32_t i = low; i <= high; i++) {
unsigned targetOffset = offset + GET_JUMP_OFFSET(pc2);
if (targetOffset != offset) {
if (!addJump(cx, targetOffset, &nextOffset, &forwardJump, &forwardLoop, stackDepth))
return;
}
getCode(targetOffset).safePoint = true;
pc2 += JUMP_OFFSET_LEN;
}
break;
}
case JSOP_TRY: {
/*
* Everything between a try and corresponding catch or finally is conditional.
* Note that there is no problem with code which is skipped by a thrown
* exception but is not caught by a later handler in the same function:
* no more code will execute, and it does not matter what is defined.
*/
isJaegerInlineable = isIonInlineable = false;
JSTryNote *tn = script_->trynotes()->vector;
JSTryNote *tnlimit = tn + script_->trynotes()->length;
for (; tn < tnlimit; tn++) {
unsigned startOffset = script_->mainOffset + tn->start;
if (startOffset == offset + 1) {
unsigned catchOffset = startOffset + tn->length;
/* This will overestimate try block code, for multiple catch/finally. */
if (catchOffset > forwardCatch)
forwardCatch = catchOffset;
if (tn->kind != JSTRY_ITER && tn->kind != JSTRY_LOOP) {
if (!addJump(cx, catchOffset, &nextOffset, &forwardJump, &forwardLoop, stackDepth))
return;
getCode(catchOffset).exceptionEntry = true;
getCode(catchOffset).safePoint = true;
}
}
}
break;
}
case JSOP_GETLOCAL: {
/*
* Watch for uses of variables not known to be defined, and mark
* them as having possible uses before definitions. Ignore GETLOCAL
* followed by a POP, these are generated for, e.g. 'var x;'
*/
jsbytecode *next = pc + JSOP_GETLOCAL_LENGTH;
if (JSOp(*next) != JSOP_POP || jumpTarget(next)) {
uint32_t local = GET_SLOTNO(pc);
if (local >= script_->nfixed) {
localsAliasStack_ = true;
break;
}
}
break;
}
case JSOP_CALLLOCAL:
case JSOP_SETLOCAL: {
uint32_t local = GET_SLOTNO(pc);
if (local >= script_->nfixed) {
localsAliasStack_ = true;
break;
}
break;
}
case JSOP_SETARG:
modifiesArguments_ = true;
isJaegerInlineable = false;
break;
case JSOP_GETPROP:
case JSOP_CALLPROP:
case JSOP_LENGTH:
case JSOP_GETELEM:
case JSOP_CALLELEM:
numPropertyReads_++;
break;
/* Additional opcodes which can be compiled but which can't be inlined. */
case JSOP_ARGUMENTS:
case JSOP_FUNAPPLY:
case JSOP_CALLEE:
isJaegerInlineable = false;
break;
case JSOP_THROW:
case JSOP_EXCEPTION:
case JSOP_DEBUGGER:
case JSOP_FUNCALL:
isIonInlineable = isJaegerInlineable = false;
break;
/* Additional opcodes which can be both compiled both normally and inline. */
case JSOP_NOP:
case JSOP_UNDEFINED:
case JSOP_GOTO:
case JSOP_DEFAULT:
case JSOP_IFEQ:
case JSOP_IFNE:
case JSOP_ITERNEXT:
case JSOP_DUP:
case JSOP_DUP2:
case JSOP_SWAP:
case JSOP_PICK:
case JSOP_BITOR:
case JSOP_BITXOR:
case JSOP_BITAND:
case JSOP_LT:
case JSOP_LE:
case JSOP_GT:
case JSOP_GE:
case JSOP_EQ:
case JSOP_NE:
case JSOP_LSH:
case JSOP_RSH:
case JSOP_URSH:
case JSOP_ADD:
case JSOP_SUB:
case JSOP_MUL:
case JSOP_DIV:
case JSOP_MOD:
case JSOP_NOT:
case JSOP_BITNOT:
case JSOP_NEG:
case JSOP_POS:
case JSOP_DELPROP:
case JSOP_DELELEM:
case JSOP_TYPEOF:
case JSOP_TYPEOFEXPR:
case JSOP_VOID:
case JSOP_TOID:
case JSOP_SETELEM:
case JSOP_IMPLICITTHIS:
case JSOP_DOUBLE:
case JSOP_STRING:
case JSOP_ZERO:
case JSOP_ONE:
case JSOP_NULL:
case JSOP_FALSE:
case JSOP_TRUE:
case JSOP_OR:
case JSOP_AND:
case JSOP_CASE:
case JSOP_STRICTEQ:
case JSOP_STRICTNE:
case JSOP_ITER:
case JSOP_MOREITER:
case JSOP_ENDITER:
case JSOP_POP:
case JSOP_GETARG:
case JSOP_CALLARG:
case JSOP_BINDGNAME:
case JSOP_UINT16:
case JSOP_NEWINIT:
case JSOP_NEWARRAY:
case JSOP_NEWOBJECT:
case JSOP_ENDINIT:
case JSOP_INITPROP:
case JSOP_INITELEM:
case JSOP_INITELEM_ARRAY:
case JSOP_SETPROP:
case JSOP_IN:
case JSOP_INSTANCEOF:
case JSOP_LINENO:
case JSOP_ENUMELEM:
case JSOP_CONDSWITCH:
case JSOP_LABEL:
case JSOP_RETRVAL:
case JSOP_GETGNAME:
case JSOP_CALLGNAME:
case JSOP_GETINTRINSIC:
case JSOP_SETINTRINSIC:
case JSOP_BINDINTRINSIC:
case JSOP_CALLINTRINSIC:
case JSOP_SETGNAME:
case JSOP_REGEXP:
case JSOP_OBJECT:
case JSOP_UINT24:
case JSOP_GETXPROP:
case JSOP_INT8:
case JSOP_INT32:
case JSOP_HOLE:
case JSOP_LOOPHEAD:
case JSOP_LOOPENTRY:
case JSOP_NOTEARG:
case JSOP_REST:
break;
default:
isJaegerCompileable = false;
isJaegerInlineable = isIonInlineable = false;
break;
}
bool jump = IsJumpOpcode(op);
/* Check basic jump opcodes, which may or may not have a fallthrough. */
if (jump) {
/* Case instructions do not push the lvalue back when branching. */
unsigned newStackDepth = stackDepth;
if (op == JSOP_CASE)
newStackDepth--;
unsigned targetOffset = offset + GET_JUMP_OFFSET(pc);
if (!addJump(cx, targetOffset, &nextOffset, &forwardJump, &forwardLoop, newStackDepth))
return;
if (op == JSOP_CASE || op == JSOP_DEFAULT)
getCode(targetOffset).safePoint = true;
}
/* Handle any fallthrough from this opcode. */
if (BytecodeFallsThrough(op)) {
JS_ASSERT(successorOffset < script_->length);
Bytecode *&nextcode = codeArray[successorOffset];
if (!nextcode) {
nextcode = alloc.new_<Bytecode>();
if (!nextcode) {
setOOM(cx);
return;
}
nextcode->stackDepth = stackDepth;
}
JS_ASSERT(nextcode->stackDepth == stackDepth);
if (jump)
nextcode->jumpFallthrough = true;
/* Treat the fallthrough of a branch instruction as a jump target. */
if (jump)
nextcode->jumpTarget = true;
else
nextcode->fallthrough = true;
}
}
JS_ASSERT(!failed());
JS_ASSERT(forwardJump == 0 && forwardLoop == 0 && forwardCatch == 0);
ranBytecode_ = true;
/*
* Always ensure that a script's arguments usage has been analyzed before
* entering the script. This allows the functionPrologue to ensure that
* arguments are always created eagerly which simplifies interp logic.
*/
if (!script_->analyzedArgsUsage())
analyzeSSA(cx);
}
/////////////////////////////////////////////////////////////////////
// Lifetime Analysis
/////////////////////////////////////////////////////////////////////
void
ScriptAnalysis::analyzeLifetimes(JSContext *cx)
{
JS_ASSERT(cx->compartment->activeAnalysis && !ranLifetimes() && !failed());
if (!ranBytecode()) {
analyzeBytecode(cx);
if (failed())
return;
}
LifoAlloc &alloc = cx->analysisLifoAlloc();
lifetimes = alloc.newArray<LifetimeVariable>(numSlots);
if (!lifetimes) {
setOOM(cx);
return;
}
PodZero(lifetimes, numSlots);
/*
* Variables which are currently dead. On forward branches to locations
* where these are live, they need to be marked as live.
*/
LifetimeVariable **saved = cx->pod_calloc<LifetimeVariable*>(numSlots);
if (!saved) {
setOOM(cx);
return;
}
unsigned savedCount = 0;
LoopAnalysis *loop = NULL;
uint32_t offset = script_->length - 1;
while (offset < script_->length) {
Bytecode *code = maybeCode(offset);
if (!code) {
offset--;
continue;
}
if (loop && code->safePoint)
loop->hasSafePoints = true;
jsbytecode *pc = script_->code + offset;
JSOp op = (JSOp) *pc;
if (op == JSOP_LOOPHEAD && code->loop) {
/*
* This is the head of a loop, we need to go and make sure that any
* variables live at the head are live at the backedge and points prior.
* For each such variable, look for the last lifetime segment in the body
* and extend it to the end of the loop.
*/
JS_ASSERT(loop == code->loop);
unsigned backedge = code->loop->backedge;
for (unsigned i = 0; i < numSlots; i++) {
if (lifetimes[i].lifetime)
extendVariable(cx, lifetimes[i], offset, backedge);
}
loop = loop->parent;
JS_ASSERT_IF(loop, loop->head < offset);
}
/* Find the last jump target in the loop, other than the initial entry point. */
if (loop && code->jumpTarget && offset != loop->entry && offset > loop->lastBlock)
loop->lastBlock = offset;
if (code->exceptionEntry) {
DebugOnly<bool> found = false;
JSTryNote *tn = script_->trynotes()->vector;
JSTryNote *tnlimit = tn + script_->trynotes()->length;
for (; tn < tnlimit; tn++) {
unsigned startOffset = script_->mainOffset + tn->start;
if (startOffset + tn->length == offset) {
/*
* Extend all live variables at exception entry to the start of
* the try block.
*/
for (unsigned i = 0; i < numSlots; i++) {
if (lifetimes[i].lifetime)
ensureVariable(lifetimes[i], startOffset - 1);
}
found = true;
break;
}
}
JS_ASSERT(found);
}
switch (op) {
case JSOP_GETARG:
case JSOP_CALLARG:
case JSOP_GETLOCAL:
case JSOP_CALLLOCAL:
case JSOP_THIS: {
uint32_t slot = GetBytecodeSlot(script_, pc);
if (!slotEscapes(slot))
addVariable(cx, lifetimes[slot], offset, saved, savedCount);
break;
}
case JSOP_SETARG:
case JSOP_SETLOCAL: {
uint32_t slot = GetBytecodeSlot(script_, pc);
if (!slotEscapes(slot))
killVariable(cx, lifetimes[slot], offset, saved, savedCount);
break;
}
case JSOP_TABLESWITCH:
/* Restore all saved variables. :FIXME: maybe do this precisely. */
for (unsigned i = 0; i < savedCount; i++) {
LifetimeVariable &var = *saved[i];
var.lifetime = alloc.new_<Lifetime>(offset, var.savedEnd, var.saved);
if (!var.lifetime) {
js_free(saved);
setOOM(cx);
return;
}
var.saved = NULL;
saved[i--] = saved[--savedCount];
}
savedCount = 0;
break;
case JSOP_TRY:
for (unsigned i = 0; i < numSlots; i++) {
LifetimeVariable &var = lifetimes[i];
if (var.ensured) {
JS_ASSERT(var.lifetime);
if (var.lifetime->start == offset)
var.ensured = false;
}
}
break;
case JSOP_NEW:
case JSOP_CALL:
case JSOP_EVAL:
case JSOP_FUNAPPLY:
case JSOP_FUNCALL:
if (loop)
loop->hasCallsLoops = true;
break;
case JSOP_LOOPENTRY:
getCode(offset).loop = loop;
break;
default:;
}
if (IsJumpOpcode(op)) {
/*
* Forward jumps need to pull in all variables which are live at
* their target offset --- the variables live before the jump are
* the union of those live at the fallthrough and at the target.
*/
uint32_t targetOffset = FollowBranch(cx, script_, offset);
/*
* Watch for 'continue' statements in the loop body, which are
* jumps to the entry offset separate from the initial jump.
*/
if (loop && loop->entry == targetOffset && loop->entry > loop->lastBlock)
loop->lastBlock = loop->entry;
if (targetOffset < offset) {
/* This is a loop back edge, no lifetime to pull in yet. */
#ifdef DEBUG
JSOp nop = JSOp(script_->code[targetOffset]);
JS_ASSERT(nop == JSOP_LOOPHEAD);
#endif
/*
* If we already have a loop, it is an outer loop and we
* need to prune the last block in the loop --- we do not
* track 'continue' statements for outer loops.
*/
if (loop && loop->entry > loop->lastBlock)
loop->lastBlock = loop->entry;
LoopAnalysis *nloop = alloc.new_<LoopAnalysis>();
if (!nloop) {
js_free(saved);
setOOM(cx);
return;
}
PodZero(nloop);
if (loop) {
loop->hasCallsLoops = true;
nloop->depth = loop->depth + 1;
}
nloop->parent = loop;
loop = nloop;
getCode(targetOffset).loop = loop;
loop->head = targetOffset;
loop->backedge = offset;
loop->lastBlock = loop->head;
/*
* Find the entry jump, which will be a GOTO for 'for' or
* 'while' loops or a fallthrough for 'do while' loops.
*/
uint32_t entry = targetOffset;
if (entry) {
do {
entry--;
} while (!maybeCode(entry));
jsbytecode *entrypc = script_->code + entry;
if (JSOp(*entrypc) == JSOP_GOTO)
loop->entry = entry + GET_JUMP_OFFSET(entrypc);
else
loop->entry = targetOffset;
} else {
/* Do-while loop at the start of the script. */
loop->entry = targetOffset;
}
JS_ASSERT(script_->code[loop->entry] == JSOP_LOOPHEAD ||
script_->code[loop->entry] == JSOP_LOOPENTRY);
} else {
for (unsigned i = 0; i < savedCount; i++) {
LifetimeVariable &var = *saved[i];
JS_ASSERT(!var.lifetime && var.saved);
if (var.live(targetOffset)) {
/*
* Jumping to a place where this variable is live. Make a new
* lifetime segment for the variable.
*/
var.lifetime = alloc.new_<Lifetime>(offset, var.savedEnd, var.saved);
if (!var.lifetime) {
js_free(saved);
setOOM(cx);
return;
}
var.saved = NULL;
saved[i--] = saved[--savedCount];
} else if (loop && !var.savedEnd) {
/*
* This jump precedes the basic block which killed the variable,
* remember it and use it for the end of the next lifetime
* segment should the variable become live again. This is needed
* for loops, as if we wrap liveness around the loop the isLive
* test below may have given the wrong answer.
*/
var.savedEnd = offset;
}
}
}
}
offset--;
}
js_free(saved);
ranLifetimes_ = true;
}
#ifdef DEBUG
void
LifetimeVariable::print() const
{
Lifetime *segment = lifetime ? lifetime : saved;
while (segment) {
printf(" (%u,%u%s)", segment->start, segment->end, segment->loopTail ? ",tail" : "");
segment = segment->next;
}
printf("\n");
}
#endif /* DEBUG */
inline void
ScriptAnalysis::addVariable(JSContext *cx, LifetimeVariable &var, unsigned offset,
LifetimeVariable **&saved, unsigned &savedCount)
{
if (var.lifetime) {
if (var.ensured)
return;
JS_ASSERT(offset < var.lifetime->start);
var.lifetime->start = offset;
} else {
if (var.saved) {
/* Remove from the list of saved entries. */
for (unsigned i = 0; i < savedCount; i++) {
if (saved[i] == &var) {
JS_ASSERT(savedCount);
saved[i--] = saved[--savedCount];
break;
}
}
}
var.lifetime = cx->analysisLifoAlloc().new_<Lifetime>(offset, var.savedEnd, var.saved);
if (!var.lifetime) {
setOOM(cx);
return;
}
var.saved = NULL;
}
}
inline void
ScriptAnalysis::killVariable(JSContext *cx, LifetimeVariable &var, unsigned offset,
LifetimeVariable **&saved, unsigned &savedCount)
{
if (!var.lifetime) {
/* Make a point lifetime indicating the write. */
Lifetime *lifetime = cx->analysisLifoAlloc().new_<Lifetime>(offset, var.savedEnd, var.saved);
if (!lifetime) {
setOOM(cx);
return;
}
if (!var.saved)
saved[savedCount++] = &var;
var.saved = lifetime;
var.saved->write = true;
var.savedEnd = 0;
return;
}
JS_ASSERT_IF(!var.ensured, offset < var.lifetime->start);
unsigned start = var.lifetime->start;
/*
* The variable is considered to be live at the bytecode which kills it
* (just not at earlier bytecodes). This behavior is needed by downstream
* register allocation (see FrameState::bestEvictReg).
*/
var.lifetime->start = offset;
var.lifetime->write = true;
if (var.ensured) {
/*
* The variable is live even before the write, due to an enclosing try
* block. We need to split the lifetime to indicate there was a write.
* We set the new interval's savedEnd to 0, since it will always be
* adjacent to the old interval, so it never needs to be extended.
*/
var.lifetime = cx->analysisLifoAlloc().new_<Lifetime>(start, 0, var.lifetime);
if (!var.lifetime) {
setOOM(cx);
return;
}
var.lifetime->end = offset;
} else {
var.saved = var.lifetime;
var.savedEnd = 0;
var.lifetime = NULL;
saved[savedCount++] = &var;
}
}
inline void
ScriptAnalysis::extendVariable(JSContext *cx, LifetimeVariable &var,
unsigned start, unsigned end)
{
JS_ASSERT(var.lifetime);
if (var.ensured) {
/*
* If we are still ensured to be live, the try block must scope over
* the loop, in which case the variable is already guaranteed to be
* live for the entire loop.
*/
JS_ASSERT(var.lifetime->start < start);
return;
}
var.lifetime->start = start;
/*
* Consider this code:
*
* while (...) { (#1)
* use x; (#2)
* ...
* x = ...; (#3)
* ...
* } (#4)
*
* Just before analyzing the while statement, there would be a live range
* from #1..#2 and a "point range" at #3. The job of extendVariable is to
* create a new live range from #3..#4.
*
* However, more extensions may be required if the definition of x is
* conditional. Consider the following.
*
* while (...) { (#1)
* use x; (#2)
* ...
* if (...) (#5)
* x = ...; (#3)
* ...
* } (#4)
*
* Assume that x is not used after the loop. Then, before extendVariable is
* run, the live ranges would be the same as before (#1..#2 and #3..#3). We
* still need to create a range from #3..#4. But, since the assignment at #3
* may never run, we also need to create a range from #2..#3. This is done
* as follows.
*
* Each time we create a Lifetime, we store the start of the most recently
* seen sequence of conditional code in the Lifetime's savedEnd field. So,
* when creating the Lifetime at #2, we set the Lifetime's savedEnd to
* #5. (The start of the most recent conditional is cached in each
* variable's savedEnd field.) Consequently, extendVariable is able to
* create a new interval from #2..#5 using the savedEnd field of the
* existing #1..#2 interval.
*/
Lifetime *segment = var.lifetime;
while (segment && segment->start < end) {
uint32_t savedEnd = segment->savedEnd;
if (!segment->next || segment->next->start >= end) {
/*
* savedEnd is only set for variables killed in the middle of the
* loop. Make a tail segment connecting the last use with the
* back edge.
*/
if (segment->end >= end) {
/* Variable known to be live after the loop finishes. */
break;
}
savedEnd = end;
}
JS_ASSERT(savedEnd <= end);
if (savedEnd > segment->end) {
Lifetime *tail = cx->analysisLifoAlloc().new_<Lifetime>(savedEnd, 0, segment->next);
if (!tail) {
setOOM(cx);
return;
}
tail->start = segment->end;
tail->loopTail = true;
/*
* Clear the segment's saved end, but preserve in the tail if this
* is the last segment in the loop and the variable is killed in an
* outer loop before the backedge.
*/
if (segment->savedEnd > end) {
JS_ASSERT(savedEnd == end);
tail->savedEnd = segment->savedEnd;
}
segment->savedEnd = 0;
segment->next = tail;
segment = tail->next;
} else {
JS_ASSERT(segment->savedEnd == 0);
segment = segment->next;
}
}
}
inline void
ScriptAnalysis::ensureVariable(LifetimeVariable &var, unsigned until)
{
JS_ASSERT(var.lifetime);
/*
* If we are already ensured, the current range we are trying to ensure
* should already be included.
*/
if (var.ensured) {
JS_ASSERT(var.lifetime->start <= until);
return;
}
JS_ASSERT(until < var.lifetime->start);
var.lifetime->start = until;
var.ensured = true;
}
/////////////////////////////////////////////////////////////////////
// SSA Analysis
/////////////////////////////////////////////////////////////////////
void
ScriptAnalysis::analyzeSSA(JSContext *cx)
{
JS_ASSERT(cx->compartment->activeAnalysis && !ranSSA() && !failed());
if (!ranLifetimes()) {
analyzeLifetimes(cx);
if (failed())
return;
}
LifoAlloc &alloc = cx->analysisLifoAlloc();
unsigned maxDepth = script_->nslots - script_->nfixed;
/*
* Current value of each variable and stack value. Empty for missing or
* untracked entries, i.e. escaping locals and arguments.
*/
SSAValueInfo *values = cx->pod_calloc<SSAValueInfo>(numSlots + maxDepth);
if (!values) {
setOOM(cx);
return;
}
struct FreeSSAValues {
SSAValueInfo *values;
FreeSSAValues(SSAValueInfo *values) : values(values) {}
~FreeSSAValues() { js_free(values); }
} free(values);
SSAValueInfo *stack = values + numSlots;
uint32_t stackDepth = 0;
for (uint32_t slot = ArgSlot(0); slot < numSlots; slot++) {
if (trackSlot(slot))
values[slot].v.initInitial(slot);
}
/*
* All target offsets for forward jumps we have seen (including ones whose
* target we have advanced past). We lazily add pending entries at these
* targets for the original value of variables modified before the branch
* rejoins.
*/
Vector<uint32_t> branchTargets(cx);
/*
* Subset of branchTargets which are exception handlers at future offsets.
* Any new value of a variable modified before the target is reached is a
* potential value at that target, along with the lazy original value.
*/
Vector<uint32_t> exceptionTargets(cx);
uint32_t offset = 0;
while (offset < script_->length) {
jsbytecode *pc = script_->code + offset;
JSOp op = (JSOp)*pc;
uint32_t successorOffset = offset + GetBytecodeLength(pc);
Bytecode *code = maybeCode(pc);
if (!code) {
offset = successorOffset;
continue;
}
if (code->exceptionEntry) {
/* Remove from exception targets list, which reflects only future targets. */
for (size_t i = 0; i < exceptionTargets.length(); i++) {
if (exceptionTargets[i] == offset) {
exceptionTargets[i] = exceptionTargets.back();
exceptionTargets.popBack();
break;
}
}
}
if (code->stackDepth > stackDepth)
PodZero(stack + stackDepth, code->stackDepth - stackDepth);
stackDepth = code->stackDepth;
if (op == JSOP_LOOPHEAD && code->loop) {
/*
* Make sure there is a pending value array for phi nodes at the
* loop head. We won't be able to clear these until we reach the
* loop's back edge.
*
* We need phi nodes for all variables which might be modified
* during the loop. This ensures that in the loop body we have
* already updated state to reflect possible changes that happen
* before the back edge, and don't need to go back and fix things
* up when we *do* get to the back edge. This could be made lazier.
*
* We don't make phi nodes for values on the stack at the head of
* the loop. These may be popped during the loop (i.e. for ITER
* loops), but in such cases the original value is pushed back.
*/
Vector<SlotValue> *&pending = code->pendingValues;
if (!pending) {
pending = cx->new_< Vector<SlotValue> >(cx);
if (!pending) {
setOOM(cx);
return;
}
}
/*
* Make phi nodes and update state for slots which are already in
* pending from previous branches to the loop head, and which are
* modified in the body of the loop.
*/
for (unsigned i = 0; i < pending->length(); i++) {
SlotValue &v = (*pending)[i];
if (v.slot < numSlots && liveness(v.slot).firstWrite(code->loop) != UINT32_MAX) {
if (v.value.kind() != SSAValue::PHI || v.value.phiOffset() != offset) {
JS_ASSERT(v.value.phiOffset() < offset);
SSAValue ov = v.value;
if (!makePhi(cx, v.slot, offset, &ov))
return;
insertPhi(cx, ov, v.value);
v.value = ov;
}
}
if (code->fallthrough || code->jumpFallthrough)
mergeValue(cx, offset, values[v.slot].v, &v);
mergeBranchTarget(cx, values[v.slot], v.slot, branchTargets, offset - 1);
values[v.slot].v = v.value;
}
/*
* Make phi nodes for all other slots which might be modified
* during the loop. This ensures that in the loop body we have
* already updated state to reflect possible changes that happen
* before the back edge, and don't need to go back and fix things
* up when we *do* get to the back edge. This could be made lazier.
*/
for (uint32_t slot = ArgSlot(0); slot < numSlots + stackDepth; slot++) {
if (slot >= numSlots || !trackSlot(slot))
continue;
if (liveness(slot).firstWrite(code->loop) == UINT32_MAX)
continue;
if (values[slot].v.kind() == SSAValue::PHI && values[slot].v.phiOffset() == offset) {
/* There is already a pending entry for this slot. */
continue;
}
SSAValue ov;
if (!makePhi(cx, slot, offset, &ov))
return;
if (code->fallthrough || code->jumpFallthrough)
insertPhi(cx, ov, values[slot].v);
mergeBranchTarget(cx, values[slot], slot, branchTargets, offset - 1);
values[slot].v = ov;
if (!pending->append(SlotValue(slot, ov))) {
setOOM(cx);
return;
}
}
} else if (code->pendingValues) {
/*
* New values at this point from a previous jump to this bytecode.
* If there is fallthrough from the previous instruction, merge
* with the current state and create phi nodes where necessary,
* otherwise replace current values with the new values.
*
* Catch blocks are artifically treated as having fallthrough, so
* that values written inside the block but not subsequently
* overwritten are picked up.
*/
bool exception = getCode(offset).exceptionEntry;
Vector<SlotValue> *pending = code->pendingValues;
for (unsigned i = 0; i < pending->length(); i++) {
SlotValue &v = (*pending)[i];
if (code->fallthrough || code->jumpFallthrough ||
(exception && values[v.slot].v.kind() != SSAValue::EMPTY)) {
mergeValue(cx, offset, values[v.slot].v, &v);
}
mergeBranchTarget(cx, values[v.slot], v.slot, branchTargets, offset);
values[v.slot].v = v.value;
}
freezeNewValues(cx, offset);
}
unsigned nuses = GetUseCount(script_, offset);
unsigned ndefs = GetDefCount(script_, offset);
JS_ASSERT(stackDepth >= nuses);
unsigned xuses = ExtendedUse(pc) ? nuses + 1 : nuses;
if (xuses) {
code->poppedValues = alloc.newArray<SSAValue>(xuses);
if (!code->poppedValues) {
setOOM(cx);
return;
}
for (unsigned i = 0; i < nuses; i++) {
SSAValue &v = stack[stackDepth - 1 - i].v;
code->poppedValues[i] = v;
v.clear();
}
if (xuses > nuses) {
/*
* For SETLOCAL, etc. opcodes, add an extra popped value
* holding the value of the local before the op.
*/
uint32_t slot = GetBytecodeSlot(script_, pc);
if (trackSlot(slot))
code->poppedValues[nuses] = values[slot].v;
else
code->poppedValues[nuses].clear();
}
if (xuses) {
SSAUseChain *useChains = alloc.newArray<SSAUseChain>(xuses);
if (!useChains) {
setOOM(cx);
return;
}
PodZero(useChains, xuses);
for (unsigned i = 0; i < xuses; i++) {
const SSAValue &v = code->poppedValues[i];
if (trackUseChain(v)) {
SSAUseChain *&uses = useChain(v);
useChains[i].popped = true;
useChains[i].offset = offset;
useChains[i].u.which = i;
useChains[i].next = uses;
uses = &useChains[i];
}
}
}
}
stackDepth -= nuses;
for (unsigned i = 0; i < ndefs; i++)
stack[stackDepth + i].v.initPushed(offset, i);
unsigned xdefs = ExtendedDef(pc) ? ndefs + 1 : ndefs;
if (xdefs) {
code->pushedUses = alloc.newArray<SSAUseChain *>(xdefs);
if (!code->pushedUses) {
setOOM(cx);
return;
}
PodZero(code->pushedUses, xdefs);
}
stackDepth += ndefs;
if (BytecodeUpdatesSlot(op)) {
uint32_t slot = GetBytecodeSlot(script_, pc);
if (trackSlot(slot)) {
mergeBranchTarget(cx, values[slot], slot, branchTargets, offset);
mergeExceptionTarget(cx, values[slot].v, slot, exceptionTargets);
values[slot].v.initWritten(slot, offset);
}
}
switch (op) {
case JSOP_GETARG:
case JSOP_GETLOCAL: {
uint32_t slot = GetBytecodeSlot(script_, pc);
if (trackSlot(slot)) {
/*
* Propagate the current value of the local to the pushed value,
* and remember it with an extended use on the opcode.
*/
stack[stackDepth - 1].v = code->poppedValues[0] = values[slot].v;
}
break;
}
/* Short circuit ops which push back one of their operands. */
case JSOP_MOREITER:
stack[stackDepth - 2].v = code->poppedValues[0];
break;
case JSOP_INITPROP:
stack[stackDepth - 1].v = code->poppedValues[1];
break;
case JSOP_SPREAD:
case JSOP_INITELEM_INC:
stack[stackDepth - 2].v = code->poppedValues[2];
break;
case JSOP_INITELEM_ARRAY:
stack[stackDepth - 1].v = code->poppedValues[1];
break;
case JSOP_INITELEM:
stack[stackDepth - 1].v = code->poppedValues[2];
break;
case JSOP_DUP:
stack[stackDepth - 1].v = stack[stackDepth - 2].v = code->poppedValues[0];
break;
case JSOP_DUP2:
stack[stackDepth - 1].v = stack[stackDepth - 3].v = code->poppedValues[0];
stack[stackDepth - 2].v = stack[stackDepth - 4].v = code->poppedValues[1];
break;
case JSOP_SWAP:
/* Swap is like pick 1. */
case JSOP_PICK: {
unsigned pickedDepth = (op == JSOP_SWAP ? 1 : pc[1]);
stack[stackDepth - 1].v = code->poppedValues[pickedDepth];
for (unsigned i = 0; i < pickedDepth; i++)
stack[stackDepth - 2 - i].v = code->poppedValues[i];
break;
}
/*
* Switch and try blocks preserve the stack between the original op
* and all case statements or exception/finally handlers.
*/
case JSOP_TABLESWITCH: {
unsigned defaultOffset = offset + GET_JUMP_OFFSET(pc);
jsbytecode *pc2 = pc + JUMP_OFFSET_LEN;
int32_t low = GET_JUMP_OFFSET(pc2);
pc2 += JUMP_OFFSET_LEN;
int32_t high = GET_JUMP_OFFSET(pc2);
pc2 += JUMP_OFFSET_LEN;
for (int32_t i = low; i <= high; i++) {
unsigned targetOffset = offset + GET_JUMP_OFFSET(pc2);
if (targetOffset != offset)
checkBranchTarget(cx, targetOffset, branchTargets, values, stackDepth);
pc2 += JUMP_OFFSET_LEN;
}
checkBranchTarget(cx, defaultOffset, branchTargets, values, stackDepth);
break;
}
case JSOP_TRY: {
JSTryNote *tn = script_->trynotes()->vector;
JSTryNote *tnlimit = tn + script_->trynotes()->length;
for (; tn < tnlimit; tn++) {
unsigned startOffset = script_->mainOffset + tn->start;
if (startOffset == offset + 1) {
unsigned catchOffset = startOffset + tn->length;
if (tn->kind != JSTRY_ITER && tn->kind != JSTRY_LOOP) {
checkBranchTarget(cx, catchOffset, branchTargets, values, stackDepth);
checkExceptionTarget(cx, catchOffset, exceptionTargets);
}
}
}
break;
}
case JSOP_THROW:
case JSOP_RETURN:
case JSOP_STOP:
case JSOP_RETRVAL:
mergeAllExceptionTargets(cx, values, exceptionTargets);
break;
default:;
}
if (IsJumpOpcode(op)) {
unsigned targetOffset = FollowBranch(cx, script_, offset);
checkBranchTarget(cx, targetOffset, branchTargets, values, stackDepth);
/*
* If this is a back edge, we're done with the loop and can freeze
* the phi values at the head now.
*/
if (targetOffset < offset)
freezeNewValues(cx, targetOffset);
}
offset = successorOffset;
}
ranSSA_ = true;
/*
* Now that we have full SSA information for the script, analyze whether
* we can avoid creating the arguments object.
*/
if (!script_->analyzedArgsUsage())
script_->setNeedsArgsObj(needsArgsObj(cx));
}
/* Get a phi node's capacity for a given length. */
static inline unsigned
PhiNodeCapacity(unsigned length)
{
if (length <= 4)
return 4;
unsigned log2;
JS_FLOOR_LOG2(log2, length - 1);
return 1 << (log2 + 1);
}
bool
ScriptAnalysis::makePhi(JSContext *cx, uint32_t slot, uint32_t offset, SSAValue *pv)
{
SSAPhiNode *node = cx->analysisLifoAlloc().new_<SSAPhiNode>();
SSAValue *options = cx->analysisLifoAlloc().newArray<SSAValue>(PhiNodeCapacity(0));
if (!node || !options) {
setOOM(cx);
return false;
}
node->slot = slot;
node->options = options;
pv->initPhi(offset, node);
return true;
}
void
ScriptAnalysis::insertPhi(JSContext *cx, SSAValue &phi, const SSAValue &v)
{
JS_ASSERT(phi.kind() == SSAValue::PHI);
SSAPhiNode *node = phi.phiNode();
/*
* Filter dupes inserted into small nodes to keep things clean and avoid
* extra type constraints, but don't bother on large phi nodes to avoid
* quadratic behavior.
*/
if (node->length <= 8) {
for (unsigned i = 0; i < node->length; i++) {
if (v == node->options[i])
return;
}
}
if (trackUseChain(v)) {
SSAUseChain *&uses = useChain(v);
SSAUseChain *use = cx->analysisLifoAlloc().new_<SSAUseChain>();
if (!use) {
setOOM(cx);
return;
}
use->popped = false;
use->offset = phi.phiOffset();
use->u.phi = node;
use->next = uses;
uses = use;
}
if (node->length < PhiNodeCapacity(node->length)) {
node->options[node->length++] = v;
return;
}
SSAValue *newOptions =
cx->analysisLifoAlloc().newArray<SSAValue>(PhiNodeCapacity(node->length + 1));
if (!newOptions) {
setOOM(cx);
return;
}
PodCopy(newOptions, node->options, node->length);
node->options = newOptions;
node->options[node->length++] = v;
}
inline void
ScriptAnalysis::mergeValue(JSContext *cx, uint32_t offset, const SSAValue &v, SlotValue *pv)
{
/* Make sure that v is accounted for in the pending value or phi value at pv. */
JS_ASSERT(v.kind() != SSAValue::EMPTY && pv->value.kind() != SSAValue::EMPTY);
if (v == pv->value)
return;
if (pv->value.kind() != SSAValue::PHI || pv->value.phiOffset() < offset) {
SSAValue ov = pv->value;
if (makePhi(cx, pv->slot, offset, &pv->value)) {
insertPhi(cx, pv->value, v);
insertPhi(cx, pv->value, ov);
}
return;
}
JS_ASSERT(pv->value.phiOffset() == offset);
insertPhi(cx, pv->value, v);
}
void
ScriptAnalysis::checkPendingValue(JSContext *cx, const SSAValue &v, uint32_t slot,
Vector<SlotValue> *pending)
{
JS_ASSERT(v.kind() != SSAValue::EMPTY);
for (unsigned i = 0; i < pending->length(); i++) {
if ((*pending)[i].slot == slot)
return;
}
if (!pending->append(SlotValue(slot, v)))
setOOM(cx);
}
void
ScriptAnalysis::checkBranchTarget(JSContext *cx, uint32_t targetOffset,
Vector<uint32_t> &branchTargets,
SSAValueInfo *values, uint32_t stackDepth)
{
unsigned targetDepth = getCode(targetOffset).stackDepth;
JS_ASSERT(targetDepth <= stackDepth);
/*
* If there is already an active branch to target, make sure its pending
* values reflect any changes made since the first branch. Otherwise, add a
* new pending branch and determine its pending values lazily.
*/
Vector<SlotValue> *&pending = getCode(targetOffset).pendingValues;
if (pending) {
for (unsigned i = 0; i < pending->length(); i++) {
SlotValue &v = (*pending)[i];
mergeValue(cx, targetOffset, values[v.slot].v, &v);
}
} else {
pending = cx->new_< Vector<SlotValue> >(cx);
if (!pending || !branchTargets.append(targetOffset)) {
setOOM(cx);
return;
}
}
/*
* Make sure there is a pending entry for each value on the stack.
* The number of stack entries at join points is usually zero, and
* we don't want to look at the active branches while popping and
* pushing values in each opcode.
*/
for (unsigned i = 0; i < targetDepth; i++) {
uint32_t slot = StackSlot(script_, i);
checkPendingValue(cx, values[slot].v, slot, pending);
}
}
void
ScriptAnalysis::checkExceptionTarget(JSContext *cx, uint32_t catchOffset,
Vector<uint32_t> &exceptionTargets)
{
JS_ASSERT(getCode(catchOffset).exceptionEntry);
/*
* The catch offset will already be in the branch targets, just check
* whether this is already a known exception target.
*/
for (unsigned i = 0; i < exceptionTargets.length(); i++) {
if (exceptionTargets[i] == catchOffset)
return;
}
if (!exceptionTargets.append(catchOffset))
setOOM(cx);
}
void
ScriptAnalysis::mergeBranchTarget(JSContext *cx, SSAValueInfo &value, uint32_t slot,
const Vector<uint32_t> &branchTargets, uint32_t currentOffset)
{
if (slot >= numSlots) {
/*
* There is no need to lazily check that there are pending values at
* branch targets for slots on the stack, these are added to pending
* eagerly.
*/
return;
}
JS_ASSERT(trackSlot(slot));
/*
* Before changing the value of a variable, make sure the old value is
* marked at the target of any branches jumping over the current opcode.
* Only look at new branch targets which have appeared since the last time
* the variable was written.
*/
for (int i = branchTargets.length() - 1; i >= value.branchSize; i--) {
if (branchTargets[i] <= currentOffset)
continue;
const Bytecode &code = getCode(branchTargets[i]);
Vector<SlotValue> *pending = code.pendingValues;
checkPendingValue(cx, value.v, slot, pending);
}
value.branchSize = branchTargets.length();
}
void
ScriptAnalysis::mergeExceptionTarget(JSContext *cx, const SSAValue &value, uint32_t slot,
const Vector<uint32_t> &exceptionTargets)
{
JS_ASSERT(trackSlot(slot));
/*
* Update the value at exception targets with the value of a variable
* before it is overwritten. Unlike mergeBranchTarget, this is done whether
* or not the overwritten value is the value of the variable at the
* original branch. Values for a variable which are written after the
* try block starts and overwritten before it is finished can still be
* seen at exception handlers via exception paths.
*/
for (unsigned i = 0; i < exceptionTargets.length(); i++) {
unsigned offset = exceptionTargets[i];
Vector<SlotValue> *pending = getCode(offset).pendingValues;
bool duplicate = false;
for (unsigned i = 0; i < pending->length(); i++) {
if ((*pending)[i].slot == slot) {
duplicate = true;
SlotValue &v = (*pending)[i];
mergeValue(cx, offset, value, &v);
break;
}
}
if (!duplicate && !pending->append(SlotValue(slot, value)))
setOOM(cx);
}
}
void
ScriptAnalysis::mergeAllExceptionTargets(JSContext *cx, SSAValueInfo *values,
const Vector<uint32_t> &exceptionTargets)
{
for (unsigned i = 0; i < exceptionTargets.length(); i++) {
Vector<SlotValue> *pending = getCode(exceptionTargets[i]).pendingValues;
for (unsigned i = 0; i < pending->length(); i++) {
const SlotValue &v = (*pending)[i];
if (trackSlot(v.slot))
mergeExceptionTarget(cx, values[v.slot].v, v.slot, exceptionTargets);
}
}
}
void
ScriptAnalysis::freezeNewValues(JSContext *cx, uint32_t offset)
{
Bytecode &code = getCode(offset);
Vector<SlotValue> *pending = code.pendingValues;
code.pendingValues = NULL;
unsigned count = pending->length();
if (count == 0) {
js_delete(pending);
return;
}
code.newValues = cx->analysisLifoAlloc().newArray<SlotValue>(count + 1);
if (!code.newValues) {
setOOM(cx);
return;
}
for (unsigned i = 0; i < count; i++)
code.newValues[i] = (*pending)[i];
code.newValues[count].slot = 0;
code.newValues[count].value.clear();
js_delete(pending);
}
bool
ScriptAnalysis::needsArgsObj(JSContext *cx, SeenVector &seen, const SSAValue &v)
{
/*
* trackUseChain is false for initial values of variables, which
* cannot hold the script's arguments object.
*/
if (!trackUseChain(v))
return false;
for (unsigned i = 0; i < seen.length(); i++) {
if (v == seen[i])
return false;
}
if (!seen.append(v)) {
cx->compartment->types.setPendingNukeTypes(cx);
return true;
}
SSAUseChain *use = useChain(v);
while (use) {
if (needsArgsObj(cx, seen, use))
return true;
use = use->next;
}
return false;
}
bool
ScriptAnalysis::needsArgsObj(JSContext *cx, SeenVector &seen, SSAUseChain *use)
{
if (!use->popped)
return needsArgsObj(cx, seen, SSAValue::PhiValue(use->offset, use->u.phi));
jsbytecode *pc = script_->code + use->offset;
JSOp op = JSOp(*pc);
if (op == JSOP_POP || op == JSOP_POPN)
return false;
/* We can read the frame's arguments directly for f.apply(x, arguments). */
if (op == JSOP_FUNAPPLY && GET_ARGC(pc) == 2 && use->u.which == 0)
return false;
/* arguments[i] can read fp->canonicalActualArg(i) directly. */
if (op == JSOP_GETELEM && use->u.which == 1)
return false;
/* arguments.length length can read fp->numActualArgs() directly. */
if (op == JSOP_LENGTH)
return false;
/* Allow assignments to non-closed locals (but not arguments). */
if (op == JSOP_SETLOCAL) {
uint32_t slot = GetBytecodeSlot(script_, pc);
if (!trackSlot(slot))
return true;
return needsArgsObj(cx, seen, SSAValue::PushedValue(use->offset, 0)) ||
needsArgsObj(cx, seen, SSAValue::WrittenVar(slot, use->offset));
}
if (op == JSOP_GETLOCAL)
return needsArgsObj(cx, seen, SSAValue::PushedValue(use->offset, 0));
return true;
}
bool
ScriptAnalysis::needsArgsObj(JSContext *cx)
{
JS_ASSERT(script_->argumentsHasVarBinding());
/*
* Always construct arguments objects when in debug mode and for generator
* scripts (generators can be suspended when speculation fails).
*/
if (cx->compartment->debugMode() || script_->isGenerator)
return true;
/*
* If the script has dynamic name accesses which could reach 'arguments',
* the parser will already have checked to ensure there are no explicit
* uses of 'arguments' in the function. If there are such uses, the script
* will be marked as definitely needing an arguments object.
*
* New accesses on 'arguments' can occur through 'eval' or the debugger
* statement. In the former case, we will dynamically detect the use and
* mark the arguments optimization as having failed.
*/
if (script_->bindingsAccessedDynamically)
return false;
/*
* Since let variables and are not tracked, we cannot soundly perform this
* analysis in their presence.
*/
if (localsAliasStack())
return true;
/*
* If a script has explicit mentions of 'arguments' and formals which may
* be stored as part of a call object, don't use lazy arguments. The
* compiler can then assume that accesses through arguments[i] will be on
* unaliased variables.
*/
if (script_->funHasAnyAliasedFormal)
return true;
unsigned pcOff = script_->argumentsBytecode() - script_->code;
SeenVector seen(cx);
return needsArgsObj(cx, seen, SSAValue::PushedValue(pcOff, 0));
}
CrossSSAValue
CrossScriptSSA::foldValue(const CrossSSAValue &cv)
{
const Frame &frame = getFrame(cv.frame);
const SSAValue &v = cv.v;
JSScript *parentScript = NULL;
ScriptAnalysis *parentAnalysis = NULL;
if (frame.parent != INVALID_FRAME) {
parentScript = getFrame(frame.parent).script;
parentAnalysis = parentScript->analysis();
}
if (v.kind() == SSAValue::VAR && v.varInitial() && parentScript) {
uint32_t slot = v.varSlot();
if (slot >= ArgSlot(0) && slot < LocalSlot(frame.script, 0)) {
uint32_t argc = GET_ARGC(frame.parentpc);
SSAValue argv = parentAnalysis->poppedValue(frame.parentpc, argc - 1 - (slot - ArgSlot(0)));
return foldValue(CrossSSAValue(frame.parent, argv));
}
}
if (v.kind() == SSAValue::PUSHED) {
jsbytecode *pc = frame.script->code + v.pushedOffset();
switch (JSOp(*pc)) {
case JSOP_THIS:
if (parentScript) {
uint32_t argc = GET_ARGC(frame.parentpc);
SSAValue thisv = parentAnalysis->poppedValue(frame.parentpc, argc);
return foldValue(CrossSSAValue(frame.parent, thisv));
}
break;
case JSOP_CALL: {
/*
* If there is a single inline callee with a single return site,
* propagate back to that.
*/
JSScript *callee = NULL;
uint32_t calleeFrame = INVALID_FRAME;
for (unsigned i = 0; i < numFrames(); i++) {
if (iterFrame(i).parent == cv.frame && iterFrame(i).parentpc == pc) {
if (callee)
return cv; /* Multiple callees */
callee = iterFrame(i).script;
calleeFrame = iterFrame(i).index;
}
}
if (callee && callee->analysis()->numReturnSites() == 1) {
ScriptAnalysis *analysis = callee->analysis();
uint32_t offset = 0;
while (offset < callee->length) {
jsbytecode *pc = callee->code + offset;
if (analysis->maybeCode(pc) && JSOp(*pc) == JSOP_RETURN)
return foldValue(CrossSSAValue(calleeFrame, analysis->poppedValue(pc, 0)));
offset += GetBytecodeLength(pc);
}
}
break;
}
case JSOP_TOID: {
/*
* TOID acts as identity for integers, so to get better precision
* we should propagate its popped values forward if it acted as
* identity.
*/
ScriptAnalysis *analysis = frame.script->analysis();
SSAValue toidv = analysis->poppedValue(pc, 0);
if (analysis->getValueTypes(toidv)->getKnownTypeTag() == JSVAL_TYPE_INT32)
return foldValue(CrossSSAValue(cv.frame, toidv));
break;
}
default:;
}
}
return cv;
}
#ifdef DEBUG
void
ScriptAnalysis::printSSA(JSContext *cx)
{
types::AutoEnterAnalysis enter(cx);
printf("\n");
RootedScript script(cx, script_);
for (unsigned offset = 0; offset < script_->length; offset++) {
Bytecode *code = maybeCode(offset);
if (!code)
continue;
jsbytecode *pc = script_->code + offset;
PrintBytecode(cx, script, pc);
SlotValue *newv = code->newValues;
if (newv) {
while (newv->slot) {
if (newv->value.kind() != SSAValue::PHI || newv->value.phiOffset() != offset) {
newv++;
continue;
}
printf(" phi ");
newv->value.print();
printf(" [");
for (unsigned i = 0; i < newv->value.phiLength(); i++) {
if (i)
printf(",");
newv->value.phiValue(i).print();
}
printf("]\n");
newv++;
}
}
unsigned nuses = GetUseCount(script_, offset);
unsigned xuses = ExtendedUse(pc) ? nuses + 1 : nuses;
for (unsigned i = 0; i < xuses; i++) {
printf(" popped%d: ", i);
code->poppedValues[i].print();
printf("\n");
}
}
printf("\n");
}
void
SSAValue::print() const
{
switch (kind()) {
case EMPTY:
printf("empty");
break;
case PUSHED:
printf("pushed:%05u#%u", pushedOffset(), pushedIndex());
break;
case VAR:
if (varInitial())
printf("initial:%u", varSlot());
else
printf("write:%05u", varOffset());
break;
case PHI:
printf("phi:%05u#%u", phiOffset(), phiSlot());
break;
default:
JS_NOT_REACHED("Bad kind");
}
}
void
ScriptAnalysis::assertMatchingDebugMode()
{
JS_ASSERT(!!script_->compartment()->debugMode() == !!originalDebugMode_);
}
#endif /* DEBUG */
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