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/*
** $Id: lpcode.c,v 1.18 2013/04/12 16:30:33 roberto Exp $
** Copyright 2007, Lua.org & PUC-Rio (see 'lpeg.html' for license)
*/
#include <limits.h>
#include "lua.h"
#include "lauxlib.h"
#include "lptypes.h"
#include "lpcode.h"
/* signals a "no-instruction */
#define NOINST -1
static const Charset fullset_ =
{{0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}};
static const Charset *fullset = &fullset_;
/*
** {======================================================
** Analysis and some optimizations
** =======================================================
*/
/*
** Check whether a charset is empty (IFail), singleton (IChar),
** full (IAny), or none of those (ISet).
*/
static Opcode charsettype (const byte *cs, int *c) {
int count = 0;
int i;
int candidate = -1; /* candidate position for a char */
for (i = 0; i < CHARSETSIZE; i++) {
int b = cs[i];
if (b == 0) {
if (count > 1) return ISet; /* else set is still empty */
}
else if (b == 0xFF) {
if (count < (i * BITSPERCHAR))
return ISet;
else count += BITSPERCHAR; /* set is still full */
}
else if ((b & (b - 1)) == 0) { /* byte has only one bit? */
if (count > 0)
return ISet; /* set is neither full nor empty */
else { /* set has only one char till now; track it */
count++;
candidate = i;
}
}
else return ISet; /* byte is neither empty, full, nor singleton */
}
switch (count) {
case 0: return IFail; /* empty set */
case 1: { /* singleton; find character bit inside byte */
int b = cs[candidate];
*c = candidate * BITSPERCHAR;
if ((b & 0xF0) != 0) { *c += 4; b >>= 4; }
if ((b & 0x0C) != 0) { *c += 2; b >>= 2; }
if ((b & 0x02) != 0) { *c += 1; }
return IChar;
}
default: {
assert(count == CHARSETSIZE * BITSPERCHAR); /* full set */
return IAny;
}
}
}
/*
** A few basic operations on Charsets
*/
static void cs_complement (Charset *cs) {
loopset(i, cs->cs[i] = ~cs->cs[i]);
}
static int cs_equal (const byte *cs1, const byte *cs2) {
loopset(i, if (cs1[i] != cs2[i]) return 0);
return 1;
}
/*
** computes whether sets cs1 and cs2 are disjoint
*/
static int cs_disjoint (const Charset *cs1, const Charset *cs2) {
loopset(i, if ((cs1->cs[i] & cs2->cs[i]) != 0) return 0;)
return 1;
}
/*
** Convert a 'char' pattern (TSet, TChar, TAny) to a charset
*/
int tocharset (TTree *tree, Charset *cs) {
switch (tree->tag) {
case TSet: { /* copy set */
loopset(i, cs->cs[i] = treebuffer(tree)[i]);
return 1;
}
case TChar: { /* only one char */
assert(0 <= tree->u.n && tree->u.n <= UCHAR_MAX);
loopset(i, cs->cs[i] = 0); /* erase all chars */
setchar(cs->cs, tree->u.n); /* add that one */
return 1;
}
case TAny: {
loopset(i, cs->cs[i] = 0xFF); /* add all to the set */
return 1;
}
default: return 0;
}
}
/*
** Checks whether a pattern has captures
*/
int hascaptures (TTree *tree) {
tailcall:
switch (tree->tag) {
case TCapture: case TRunTime:
return 1;
default: {
switch (numsiblings[tree->tag]) {
case 1: /* return hascaptures(sib1(tree)); */
tree = sib1(tree); goto tailcall;
case 2:
if (hascaptures(sib1(tree))) return 1;
/* else return hascaptures(sib2(tree)); */
tree = sib2(tree); goto tailcall;
default: assert(numsiblings[tree->tag] == 0); return 0;
}
}
}
}
/*
** Checks how a pattern behaves regarding the empty string,
** in one of two different ways:
** A pattern is *nullable* if it can match without consuming any character;
** A pattern is *nofail* if it never fails for any string
** (including the empty string).
** The difference is only for predicates and run-time captures;
** for other patterns, the two properties are equivalent.
** (With predicates, &'a' is nullable but not nofail. Of course,
** nofail => nullable.)
** These functions are all convervative in the following way:
** p is nullable => nullable(p)
** nofail(p) => p cannot fail
** The function assumes that TOpenCall is not nullable;
** this will be checked again when the grammar is fixed.)
** Run-time captures can do whatever they want, so the result
** is conservative.
*/
int checkaux (TTree *tree, int pred) {
tailcall:
switch (tree->tag) {
case TChar: case TSet: case TAny:
case TFalse: case TOpenCall:
return 0; /* not nullable */
case TRep: case TTrue:
return 1; /* no fail */
case TNot: case TBehind: /* can match empty, but can fail */
if (pred == PEnofail) return 0;
else return 1; /* PEnullable */
case TAnd: /* can match empty; fail iff body does */
if (pred == PEnullable) return 1;
/* else return checkaux(sib1(tree), pred); */
tree = sib1(tree); goto tailcall;
case TRunTime: /* can fail; match empty iff body does */
if (pred == PEnofail) return 0;
/* else return checkaux(sib1(tree), pred); */
tree = sib1(tree); goto tailcall;
case TSeq:
if (!checkaux(sib1(tree), pred)) return 0;
/* else return checkaux(sib2(tree), pred); */
tree = sib2(tree); goto tailcall;
case TChoice:
if (checkaux(sib2(tree), pred)) return 1;
/* else return checkaux(sib1(tree), pred); */
tree = sib1(tree); goto tailcall;
case TCapture: case TGrammar: case TRule:
/* return checkaux(sib1(tree), pred); */
tree = sib1(tree); goto tailcall;
case TCall: /* return checkaux(sib2(tree), pred); */
tree = sib2(tree); goto tailcall;
default: assert(0); return 0;
};
}
/*
** number of characters to match a pattern (or -1 if variable)
** ('count' avoids infinite loops for grammars)
*/
int fixedlenx (TTree *tree, int count, int len) {
tailcall:
switch (tree->tag) {
case TChar: case TSet: case TAny:
return len + 1;
case TFalse: case TTrue: case TNot: case TAnd: case TBehind:
return len;
case TRep: case TRunTime: case TOpenCall:
return -1;
case TCapture: case TRule: case TGrammar:
/* return fixedlenx(sib1(tree), count); */
tree = sib1(tree); goto tailcall;
case TCall:
if (count++ >= MAXRULES)
return -1; /* may be a loop */
/* else return fixedlenx(sib2(tree), count); */
tree = sib2(tree); goto tailcall;
case TSeq: {
len = fixedlenx(sib1(tree), count, len);
if (len < 0) return -1;
/* else return fixedlenx(sib2(tree), count, len); */
tree = sib2(tree); goto tailcall;
}
case TChoice: {
int n1, n2;
n1 = fixedlenx(sib1(tree), count, len);
if (n1 < 0) return -1;
n2 = fixedlenx(sib2(tree), count, len);
if (n1 == n2) return n1;
else return -1;
}
default: assert(0); return 0;
};
}
/*
** Computes the 'first set' of a pattern.
** The result is a conservative aproximation:
** match p ax -> x' for some x ==> a in first(p).
** The set 'follow' is the first set of what follows the
** pattern (full set if nothing follows it).
** The function returns 0 when this set can be used for
** tests that avoid the pattern altogether.
** A non-zero return can happen for two reasons:
** 1) match p '' -> '' ==> returns 1.
** (tests cannot be used because they always fail for an empty input)
** 2) there is a match-time capture ==> returns 2.
** (match-time captures should not be avoided by optimizations)
*/
static int getfirst (TTree *tree, const Charset *follow, Charset *firstset) {
tailcall:
switch (tree->tag) {
case TChar: case TSet: case TAny: {
tocharset(tree, firstset);
return 0;
}
case TTrue: {
loopset(i, firstset->cs[i] = follow->cs[i]);
return 1;
}
case TFalse: {
loopset(i, firstset->cs[i] = 0);
return 0;
}
case TChoice: {
Charset csaux;
int e1 = getfirst(sib1(tree), follow, firstset);
int e2 = getfirst(sib2(tree), follow, &csaux);
loopset(i, firstset->cs[i] |= csaux.cs[i]);
return e1 | e2;
}
case TSeq: {
if (!nullable(sib1(tree))) {
/* return getfirst(sib1(tree), fullset, firstset); */
tree = sib1(tree); follow = fullset; goto tailcall;
}
else { /* FIRST(p1 p2, fl) = FIRST(p1, FIRST(p2, fl)) */
Charset csaux;
int e2 = getfirst(sib2(tree), follow, &csaux);
int e1 = getfirst(sib1(tree), &csaux, firstset);
if (e1 == 0) return 0; /* 'e1' ensures that first can be used */
else if ((e1 | e2) & 2) /* one of the children has a matchtime? */
return 2; /* pattern has a matchtime capture */
else return e2; /* else depends on 'e2' */
}
}
case TRep: {
getfirst(sib1(tree), follow, firstset);
loopset(i, firstset->cs[i] |= follow->cs[i]);
return 1; /* accept the empty string */
}
case TCapture: case TGrammar: case TRule: {
/* return getfirst(sib1(tree), follow, firstset); */
tree = sib1(tree); goto tailcall;
}
case TRunTime: { /* function invalidates any follow info. */
int e = getfirst(sib1(tree), fullset, firstset);
if (e) return 2; /* function is not "protected"? */
else return 0; /* pattern inside capture ensures first can be used */
}
case TCall: {
/* return getfirst(sib2(tree), follow, firstset); */
tree = sib2(tree); goto tailcall;
}
case TAnd: {
int e = getfirst(sib1(tree), follow, firstset);
loopset(i, firstset->cs[i] &= follow->cs[i]);
return e;
}
case TNot: {
if (tocharset(sib1(tree), firstset)) {
cs_complement(firstset);
return 1;
}
/* else go through */
}
case TBehind: { /* instruction gives no new information */
/* call 'getfirst' to check for math-time captures */
int e = getfirst(sib1(tree), follow, firstset);
loopset(i, firstset->cs[i] = follow->cs[i]); /* uses follow */
return e | 1; /* always can accept the empty string */
}
default: assert(0); return 0;
}
}
/*
** If it returns true, then pattern can fail only depending on the next
** character of the subject
*/
static int headfail (TTree *tree) {
tailcall:
switch (tree->tag) {
case TChar: case TSet: case TAny: case TFalse:
return 1;
case TTrue: case TRep: case TRunTime: case TNot:
case TBehind:
return 0;
case TCapture: case TGrammar: case TRule: case TAnd:
tree = sib1(tree); goto tailcall; /* return headfail(sib1(tree)); */
case TCall:
tree = sib2(tree); goto tailcall; /* return headfail(sib2(tree)); */
case TSeq:
if (!nofail(sib2(tree))) return 0;
/* else return headfail(sib1(tree)); */
tree = sib1(tree); goto tailcall;
case TChoice:
if (!headfail(sib1(tree))) return 0;
/* else return headfail(sib2(tree)); */
tree = sib2(tree); goto tailcall;
default: assert(0); return 0;
}
}
/*
** Check whether the code generation for the given tree can benefit
** from a follow set (to avoid computing the follow set when it is
** not needed)
*/
static int needfollow (TTree *tree) {
tailcall:
switch (tree->tag) {
case TChar: case TSet: case TAny:
case TFalse: case TTrue: case TAnd: case TNot:
case TRunTime: case TGrammar: case TCall: case TBehind:
return 0;
case TChoice: case TRep:
return 1;
case TCapture:
tree = sib1(tree); goto tailcall;
case TSeq:
tree = sib2(tree); goto tailcall;
default: assert(0); return 0;
}
}
/* }====================================================== */
/*
** {======================================================
** Code generation
** =======================================================
*/
/*
** size of an instruction
*/
int sizei (const Instruction *i) {
switch((Opcode)i->i.code) {
case ISet: case ISpan: return CHARSETINSTSIZE;
case ITestSet: return CHARSETINSTSIZE + 1;
case ITestChar: case ITestAny: case IChoice: case IJmp:
case ICall: case IOpenCall: case ICommit: case IPartialCommit:
case IBackCommit: return 2;
default: return 1;
}
}
/*
** state for the compiler
*/
typedef struct CompileState {
Pattern *p; /* pattern being compiled */
int ncode; /* next position in p->code to be filled */
lua_State *L;
} CompileState;
/*
** code generation is recursive; 'opt' indicates that the code is
** being generated under a 'IChoice' operator jumping to its end.
** 'tt' points to a previous test protecting this code. 'fl' is
** the follow set of the pattern.
*/
static void codegen (CompileState *compst, TTree *tree, int opt, int tt,
const Charset *fl);
void reallocprog (lua_State *L, Pattern *p, int nsize) {
void *ud;
lua_Alloc f = lua_getallocf(L, &ud);
void *newblock = f(ud, p->code, p->codesize * sizeof(Instruction),
nsize * sizeof(Instruction));
if (newblock == NULL && nsize > 0)
luaL_error(L, "not enough memory");
p->code = (Instruction *)newblock;
p->codesize = nsize;
}
static int nextinstruction (CompileState *compst) {
int size = compst->p->codesize;
if (compst->ncode >= size)
reallocprog(compst->L, compst->p, size * 2);
return compst->ncode++;
}
#define getinstr(cs,i) ((cs)->p->code[i])
static int addinstruction (CompileState *compst, Opcode op, int aux) {
int i = nextinstruction(compst);
getinstr(compst, i).i.code = op;
getinstr(compst, i).i.aux = aux;
return i;
}
static int addoffsetinst (CompileState *compst, Opcode op) {
int i = addinstruction(compst, op, 0); /* instruction */
addinstruction(compst, (Opcode)0, 0); /* open space for offset */
assert(op == ITestSet || sizei(&getinstr(compst, i)) == 2);
return i;
}
static void setoffset (CompileState *compst, int instruction, int offset) {
getinstr(compst, instruction + 1).offset = offset;
}
/*
** Add a capture instruction:
** 'op' is the capture instruction; 'cap' the capture kind;
** 'key' the key into ktable; 'aux' is optional offset
**
*/
static int addinstcap (CompileState *compst, Opcode op, int cap, int key,
int aux) {
int i = addinstruction(compst, op, joinkindoff(cap, aux));
getinstr(compst, i).i.key = key;
return i;
}
#define gethere(compst) ((compst)->ncode)
#define target(code,i) ((i) + code[i + 1].offset)
static void jumptothere (CompileState *compst, int instruction, int target) {
if (instruction >= 0)
setoffset(compst, instruction, target - instruction);
}
static void jumptohere (CompileState *compst, int instruction) {
jumptothere(compst, instruction, gethere(compst));
}
/*
** Code an IChar instruction, or IAny if there is an equivalent
** test dominating it
*/
static void codechar (CompileState *compst, int c, int tt) {
if (tt >= 0 && getinstr(compst, tt).i.code == ITestChar &&
getinstr(compst, tt).i.aux == c)
addinstruction(compst, IAny, 0);
else
addinstruction(compst, IChar, c);
}
/*
** Add a charset posfix to an instruction
*/
static void addcharset (CompileState *compst, const byte *cs) {
int p = gethere(compst);
int i;
for (i = 0; i < (int)CHARSETINSTSIZE - 1; i++)
nextinstruction(compst); /* space for buffer */
/* fill buffer with charset */
loopset(j, getinstr(compst, p).buff[j] = cs[j]);
}
/*
** code a char set, optimizing unit sets for IChar, "complete"
** sets for IAny, and empty sets for IFail; also use an IAny
** when instruction is dominated by an equivalent test.
*/
static void codecharset (CompileState *compst, const byte *cs, int tt) {
int c = 0; /* (=) to avoid warnings */
Opcode op = charsettype(cs, &c);
switch (op) {
case IChar: codechar(compst, c, tt); break;
case ISet: { /* non-trivial set? */
if (tt >= 0 && getinstr(compst, tt).i.code == ITestSet &&
cs_equal(cs, getinstr(compst, tt + 2).buff))
addinstruction(compst, IAny, 0);
else {
addinstruction(compst, ISet, 0);
addcharset(compst, cs);
}
break;
}
default: addinstruction(compst, op, c); break;
}
}
/*
** code a test set, optimizing unit sets for ITestChar, "complete"
** sets for ITestAny, and empty sets for IJmp (always fails).
** 'e' is true iff test should accept the empty string. (Test
** instructions in the current VM never accept the empty string.)
*/
static int codetestset (CompileState *compst, Charset *cs, int e) {
if (e) return NOINST; /* no test */
else {
int c = 0;
Opcode op = charsettype(cs->cs, &c);
switch (op) {
case IFail: return addoffsetinst(compst, IJmp); /* always jump */
case IAny: return addoffsetinst(compst, ITestAny);
case IChar: {
int i = addoffsetinst(compst, ITestChar);
getinstr(compst, i).i.aux = c;
return i;
}
case ISet: {
int i = addoffsetinst(compst, ITestSet);
addcharset(compst, cs->cs);
return i;
}
default: assert(0); return 0;
}
}
}
/*
** Find the final destination of a sequence of jumps
*/
static int finaltarget (Instruction *code, int i) {
while (code[i].i.code == IJmp)
i = target(code, i);
return i;
}
/*
** final label (after traversing any jumps)
*/
static int finallabel (Instruction *code, int i) {
return finaltarget(code, target(code, i));
}
/*
** <behind(p)> == behind n; <p> (where n = fixedlen(p))
*/
static void codebehind (CompileState *compst, TTree *tree) {
if (tree->u.n > 0)
addinstruction(compst, IBehind, tree->u.n);
codegen(compst, sib1(tree), 0, NOINST, fullset);
}
/*
** Choice; optimizations:
** - when p1 is headfail
** - when first(p1) and first(p2) are disjoint; than
** a character not in first(p1) cannot go to p1, and a character
** in first(p1) cannot go to p2 (at it is not in first(p2)).
** (The optimization is not valid if p1 accepts the empty string,
** as then there is no character at all...)
** - when p2 is empty and opt is true; a IPartialCommit can resuse
** the Choice already active in the stack.
*/
static void codechoice (CompileState *compst, TTree *p1, TTree *p2, int opt,
const Charset *fl) {
int emptyp2 = (p2->tag == TTrue);
Charset cs1, cs2;
int e1 = getfirst(p1, fullset, &cs1);
if (headfail(p1) ||
(!e1 && (getfirst(p2, fl, &cs2), cs_disjoint(&cs1, &cs2)))) {
/* <p1 / p2> == test (fail(p1)) -> L1 ; p1 ; jmp L2; L1: p2; L2: */
int test = codetestset(compst, &cs1, 0);
int jmp = NOINST;
codegen(compst, p1, 0, test, fl);
if (!emptyp2)
jmp = addoffsetinst(compst, IJmp);
jumptohere(compst, test);
codegen(compst, p2, opt, NOINST, fl);
jumptohere(compst, jmp);
}
else if (opt && emptyp2) {
/* p1? == IPartialCommit; p1 */
jumptohere(compst, addoffsetinst(compst, IPartialCommit));
codegen(compst, p1, 1, NOINST, fullset);
}
else {
/* <p1 / p2> ==
test(fail(p1)) -> L1; choice L1; <p1>; commit L2; L1: <p2>; L2: */
int pcommit;
int test = codetestset(compst, &cs1, e1);
int pchoice = addoffsetinst(compst, IChoice);
codegen(compst, p1, emptyp2, test, fullset);
pcommit = addoffsetinst(compst, ICommit);
jumptohere(compst, pchoice);
jumptohere(compst, test);
codegen(compst, p2, opt, NOINST, fl);
jumptohere(compst, pcommit);
}
}
/*
** And predicate
** optimization: fixedlen(p) = n ==> <&p> == <p>; behind n
** (valid only when 'p' has no captures)
*/
static void codeand (CompileState *compst, TTree *tree, int tt) {
int n = fixedlen(tree);
if (n >= 0 && n <= MAXBEHIND && !hascaptures(tree)) {
codegen(compst, tree, 0, tt, fullset);
if (n > 0)
addinstruction(compst, IBehind, n);
}
else { /* default: Choice L1; p1; BackCommit L2; L1: Fail; L2: */
int pcommit;
int pchoice = addoffsetinst(compst, IChoice);
codegen(compst, tree, 0, tt, fullset);
pcommit = addoffsetinst(compst, IBackCommit);
jumptohere(compst, pchoice);
addinstruction(compst, IFail, 0);
jumptohere(compst, pcommit);
}
}
/*
** Captures: if pattern has fixed (and not too big) length, use
** a single IFullCapture instruction after the match; otherwise,
** enclose the pattern with OpenCapture - CloseCapture.
*/
static void codecapture (CompileState *compst, TTree *tree, int tt,
const Charset *fl) {
int len = fixedlen(sib1(tree));
if (len >= 0 && len <= MAXOFF && !hascaptures(sib1(tree))) {
codegen(compst, sib1(tree), 0, tt, fl);
addinstcap(compst, IFullCapture, tree->cap, tree->key, len);
}
else {
addinstcap(compst, IOpenCapture, tree->cap, tree->key, 0);
codegen(compst, sib1(tree), 0, tt, fl);
addinstcap(compst, ICloseCapture, Cclose, 0, 0);
}
}
static void coderuntime (CompileState *compst, TTree *tree, int tt) {
addinstcap(compst, IOpenCapture, Cgroup, tree->key, 0);
codegen(compst, sib1(tree), 0, tt, fullset);
addinstcap(compst, ICloseRunTime, Cclose, 0, 0);
}
/*
** Repetion; optimizations:
** When pattern is a charset, can use special instruction ISpan.
** When pattern is head fail, or if it starts with characters that
** are disjoint from what follows the repetions, a simple test
** is enough (a fail inside the repetition would backtrack to fail
** again in the following pattern, so there is no need for a choice).
** When 'opt' is true, the repetion can reuse the Choice already
** active in the stack.
*/
static void coderep (CompileState *compst, TTree *tree, int opt,
const Charset *fl) {
Charset st;
if (tocharset(tree, &st)) {
addinstruction(compst, ISpan, 0);
addcharset(compst, st.cs);
}
else {
int e1 = getfirst(tree, fullset, &st);
if (headfail(tree) || (!e1 && cs_disjoint(&st, fl))) {
/* L1: test (fail(p1)) -> L2; <p>; jmp L1; L2: */
int jmp;
int test = codetestset(compst, &st, 0);
codegen(compst, tree, opt, test, fullset);
jmp = addoffsetinst(compst, IJmp);
jumptohere(compst, test);
jumptothere(compst, jmp, test);
}
else {
/* test(fail(p1)) -> L2; choice L2; L1: <p>; partialcommit L1; L2: */
/* or (if 'opt'): partialcommit L1; L1: <p>; partialcommit L1; */
int commit, l2;
int test = codetestset(compst, &st, e1);
int pchoice = NOINST;
if (opt)
jumptohere(compst, addoffsetinst(compst, IPartialCommit));
else
pchoice = addoffsetinst(compst, IChoice);
l2 = gethere(compst);
codegen(compst, tree, 0, NOINST, fullset);
commit = addoffsetinst(compst, IPartialCommit);
jumptothere(compst, commit, l2);
jumptohere(compst, pchoice);
jumptohere(compst, test);
}
}
}
/*
** Not predicate; optimizations:
** In any case, if first test fails, 'not' succeeds, so it can jump to
** the end. If pattern is headfail, that is all (it cannot fail
** in other parts); this case includes 'not' of simple sets. Otherwise,
** use the default code (a choice plus a failtwice).
*/
static void codenot (CompileState *compst, TTree *tree) {
Charset st;
int e = getfirst(tree, fullset, &st);
int test = codetestset(compst, &st, e);
if (headfail(tree)) /* test (fail(p1)) -> L1; fail; L1: */
addinstruction(compst, IFail, 0);
else {
/* test(fail(p))-> L1; choice L1; <p>; failtwice; L1: */
int pchoice = addoffsetinst(compst, IChoice);
codegen(compst, tree, 0, NOINST, fullset);
addinstruction(compst, IFailTwice, 0);
jumptohere(compst, pchoice);
}
jumptohere(compst, test);
}
/*
** change open calls to calls, using list 'positions' to find
** correct offsets; also optimize tail calls
*/
static void correctcalls (CompileState *compst, int *positions,
int from, int to) {
int i;
Instruction *code = compst->p->code;
for (i = from; i < to; i += sizei(&code[i])) {
if (code[i].i.code == IOpenCall) {
int n = code[i].i.key; /* rule number */
int rule = positions[n]; /* rule position */
assert(rule == from || code[rule - 1].i.code == IRet);
if (code[finaltarget(code, i + 2)].i.code == IRet) /* call; ret ? */
code[i].i.code = IJmp; /* tail call */
else
code[i].i.code = ICall;
jumptothere(compst, i, rule); /* call jumps to respective rule */
}
}
assert(i == to);
}
/*
** Code for a grammar:
** call L1; jmp L2; L1: rule 1; ret; rule 2; ret; ...; L2:
*/
static void codegrammar (CompileState *compst, TTree *grammar) {
int positions[MAXRULES];
int rulenumber = 0;
TTree *rule;
int firstcall = addoffsetinst(compst, ICall); /* call initial rule */
int jumptoend = addoffsetinst(compst, IJmp); /* jump to the end */
int start = gethere(compst); /* here starts the initial rule */
jumptohere(compst, firstcall);
for (rule = sib1(grammar); rule->tag == TRule; rule = sib2(rule)) {
positions[rulenumber++] = gethere(compst); /* save rule position */
codegen(compst, sib1(rule), 0, NOINST, fullset); /* code rule */
addinstruction(compst, IRet, 0);
}
assert(rule->tag == TTrue);
jumptohere(compst, jumptoend);
correctcalls(compst, positions, start, gethere(compst));
}
static void codecall (CompileState *compst, TTree *call) {
int c = addoffsetinst(compst, IOpenCall); /* to be corrected later */
getinstr(compst, c).i.key = sib2(call)->cap; /* rule number */
assert(sib2(call)->tag == TRule);
}
/*
** Code first child of a sequence
** (second child is called in-place to allow tail call)
** Return 'tt' for second child
*/
static int codeseq1 (CompileState *compst, TTree *p1, TTree *p2,
int tt, const Charset *fl) {
if (needfollow(p1)) {
Charset fl1;
getfirst(p2, fl, &fl1); /* p1 follow is p2 first */
codegen(compst, p1, 0, tt, &fl1);
}
else /* use 'fullset' as follow */
codegen(compst, p1, 0, tt, fullset);
if (fixedlen(p1) != 0) /* can 'p1' consume anything? */
return NOINST; /* invalidate test */
else return tt; /* else 'tt' still protects sib2 */
}
/*
** Main code-generation function: dispatch to auxiliar functions
** according to kind of tree
*/
static void codegen (CompileState *compst, TTree *tree, int opt, int tt,
const Charset *fl) {
tailcall:
switch (tree->tag) {
case TChar: codechar(compst, tree->u.n, tt); break;
case TAny: addinstruction(compst, IAny, 0); break;
case TSet: codecharset(compst, treebuffer(tree), tt); break;
case TTrue: break;
case TFalse: addinstruction(compst, IFail, 0); break;
case TChoice: codechoice(compst, sib1(tree), sib2(tree), opt, fl); break;
case TRep: coderep(compst, sib1(tree), opt, fl); break;
case TBehind: codebehind(compst, tree); break;
case TNot: codenot(compst, sib1(tree)); break;
case TAnd: codeand(compst, sib1(tree), tt); break;
case TCapture: codecapture(compst, tree, tt, fl); break;
case TRunTime: coderuntime(compst, tree, tt); break;
case TGrammar: codegrammar(compst, tree); break;
case TCall: codecall(compst, tree); break;
case TSeq: {
tt = codeseq1(compst, sib1(tree), sib2(tree), tt, fl); /* code 'p1' */
/* codegen(compst, p2, opt, tt, fl); */
tree = sib2(tree); goto tailcall;
}
default: assert(0);
}
}
/*
** Optimize jumps and other jump-like instructions.
** * Update labels of instructions with labels to their final
** destinations (e.g., choice L1; ... L1: jmp L2: becomes
** choice L2)
** * Jumps to other instructions that do jumps become those
** instructions (e.g., jump to return becomes a return; jump
** to commit becomes a commit)
*/
static void peephole (CompileState *compst) {
Instruction *code = compst->p->code;
int i;
for (i = 0; i < compst->ncode; i += sizei(&code[i])) {
switch (code[i].i.code) {
case IChoice: case ICall: case ICommit: case IPartialCommit:
case IBackCommit: case ITestChar: case ITestSet:
case ITestAny: { /* instructions with labels */
jumptothere(compst, i, finallabel(code, i)); /* optimize label */
break;
}
case IJmp: {
int ft = finaltarget(code, i);
switch (code[ft].i.code) { /* jumping to what? */
case IRet: case IFail: case IFailTwice:
case IEnd: { /* instructions with unconditional implicit jumps */
code[i] = code[ft]; /* jump becomes that instruction */
code[i + 1].i.code = IAny; /* 'no-op' for target position */
break;
}
case ICommit: case IPartialCommit:
case IBackCommit: { /* inst. with unconditional explicit jumps */
int fft = finallabel(code, ft);
code[i] = code[ft]; /* jump becomes that instruction... */
jumptothere(compst, i, fft); /* but must correct its offset */
i--; /* reoptimize its label */
break;
}
default: {
jumptothere(compst, i, ft); /* optimize label */
break;
}
}
break;
}
default: break;
}
}
assert(code[i - 1].i.code == IEnd);
}
/*
** Compile a pattern
*/
Instruction *compile (lua_State *L, Pattern *p) {
CompileState compst;
compst.p = p; compst.ncode = 0; compst.L = L;
reallocprog(L, p, 2); /* minimum initial size */
codegen(&compst, p->tree, 0, NOINST, fullset);
addinstruction(&compst, IEnd, 0);
reallocprog(L, p, compst.ncode); /* set final size */
peephole(&compst);
return p->code;
}
/* }====================================================== */