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simplify.c
196 lines (179 loc) · 6.72 KB
/
simplify.c
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/* simplify.c -- basic simplification pass */
/* Copyright (c) 2010-2015 Alex Shinn. All rights reserved. */
/* BSD-style license: http://synthcode.com/license.txt */
#include "chibi/eval.h"
#if SEXP_USE_SIMPLIFY
#define simplify_it(it) ((it) = simplify(ctx, it, substs, lambda))
static sexp simplify (sexp ctx, sexp ast, sexp init_substs, sexp lambda) {
int check;
sexp ls1, ls2, p1, p2, sv;
sexp_gc_var5(res, substs, tmp, app, ctx2);
if (!sexp_pointerp(ast))
return ast;
sexp_gc_preserve5(ctx, res, substs, tmp, app, ctx2);
res = ast; /* return the ast as-is by default */
substs = init_substs;
switch (sexp_pointer_tag(res)) {
case SEXP_PAIR:
/* don't simplify the operator if it's a lambda because we
simplify that as a special case below, with the appropriate
substs list */
app = sexp_list1(ctx, sexp_lambdap(sexp_car(res)) ? sexp_car(res)
: (tmp=simplify(ctx, sexp_car(res), substs, lambda)));
sexp_pair_source(app) = sexp_pair_source(res);
for (ls1=sexp_cdr(res); sexp_pairp(ls1); ls1=sexp_cdr(ls1)) {
sexp_push(ctx, app, tmp=simplify(ctx, sexp_car(ls1), substs, lambda));
if (sexp_pairp(app)) sexp_pair_source(app) = sexp_pair_source(ls1);
}
app = sexp_nreverse(ctx, app);
/* app now holds a copy of the list, and is the default result
(res = app below) if we don't replace it with a simplification */
if (sexp_opcodep(sexp_car(app))) {
/* opcode app - right now we just constant fold arithmetic */
if (sexp_opcode_class(sexp_car(app)) == SEXP_OPC_ARITHMETIC) {
for (check=1, ls1=sexp_cdr(app); sexp_pairp(ls1); ls1=sexp_cdr(ls1)) {
if (sexp_pointerp(sexp_car(ls1)) && ! sexp_litp(sexp_car(ls1))) {
check = 0;
break;
}
}
if (check) {
ctx2 = sexp_make_eval_context(ctx, NULL, sexp_context_env(ctx), 0, 0);
sexp_generate(ctx2, 0, 0, 0, app);
res = sexp_complete_bytecode(ctx2);
if (! sexp_exceptionp(res)) {
tmp = sexp_make_vector(ctx2, 0, SEXP_VOID);
tmp = sexp_make_procedure(ctx2, SEXP_ZERO, SEXP_ZERO, res, tmp);
if (! sexp_exceptionp(tmp)) {
tmp = sexp_apply_no_err_handler(ctx2, tmp, SEXP_NULL);
if (! sexp_exceptionp(tmp))
app = sexp_make_lit(ctx2, tmp);
}
}
}
}
} else if (lambda && sexp_lambdap(sexp_car(app))) { /* let */
p1 = NULL;
p2 = sexp_lambda_params(sexp_car(app));
ls1 = app;
ls2 = sexp_cdr(app);
sv = sexp_lambda_sv(sexp_car(app));
/* inline constants and immutable references */
if (sexp_length(ctx, p2) == sexp_length(ctx, ls2)) {
for ( ; sexp_pairp(ls2); ls2=sexp_cdr(ls2), p2=sexp_cdr(p2)) {
if (sexp_not(sexp_memq(ctx, sexp_car(p2), sv))
&& (! sexp_pointerp(sexp_car(ls2)) || sexp_litp(sexp_car(ls2))
/* disable inline references for now */
|| (0 && sexp_refp(sexp_car(ls2))
&& sexp_lambdap(sexp_ref_loc(sexp_car(ls2)))
&& sexp_not(sexp_memq(ctx, sexp_ref_name(sexp_car(ls2)),
sexp_lambda_sv(sexp_ref_loc(sexp_car(ls2)))))))) {
tmp = sexp_cons(ctx, sexp_car(app), sexp_car(ls2));
tmp = sexp_cons(ctx, sexp_car(p2), tmp);
sexp_push(ctx, substs, tmp);
sexp_cdr(ls1) = sexp_cdr(ls2);
if (p1)
sexp_cdr(p1) = sexp_cdr(p2);
else
sexp_lambda_params(sexp_car(app)) = sexp_cdr(p2);
} else {
p1 = p2;
ls1 = ls2;
}
}
sexp_lambda_body(sexp_car(app))
= simplify(ctx, sexp_lambda_body(sexp_car(app)), substs, sexp_car(app));
/* TODO: Revisit this - it causes GC problems in rare cases. */
/* if (sexp_nullp(sexp_cdr(app)) */
/* && sexp_nullp(sexp_lambda_params(sexp_car(app))) */
/* && sexp_nullp(sexp_lambda_defs(sexp_car(app)))) */
/* app = sexp_lambda_body(sexp_car(app)); */
} else if (sexp_lambdap(sexp_car(app))) {
sexp_lambda_body(sexp_car(app))
= simplify(ctx, sexp_lambda_body(sexp_car(app)), substs, sexp_car(app));
}
}
res = app;
break;
case SEXP_LAMBDA:
sexp_lambda_body(res) = simplify(ctx, sexp_lambda_body(res), substs, res);
break;
case SEXP_CND:
tmp = simplify(ctx, sexp_cnd_test(res), substs, lambda);
if (sexp_litp(tmp) || ! sexp_pointerp(tmp)) {
res = sexp_not((sexp_litp(tmp) ? sexp_lit_value(tmp) : tmp))
? sexp_cnd_fail(res) : sexp_cnd_pass(res);
res = simplify(ctx, res, substs, lambda);
} else {
sexp_cnd_test(res) = tmp;
simplify_it(sexp_cnd_pass(res));
simplify_it(sexp_cnd_fail(res));
}
break;
case SEXP_REF:
tmp = sexp_ref_name(res);
for (ls1=substs; sexp_pairp(ls1); ls1=sexp_cdr(ls1))
if ((sexp_caar(ls1) == tmp) && (sexp_cadar(ls1) == sexp_ref_loc(res))) {
res = sexp_cddar(ls1);
break;
}
break;
case SEXP_SET:
simplify_it(sexp_set_value(res));
break;
case SEXP_SEQ:
app = SEXP_NULL;
for (ls2=sexp_seq_ls(res); sexp_pairp(ls2); ls2=sexp_cdr(ls2)) {
tmp = simplify(ctx, sexp_car(ls2), substs, lambda);
if (! (sexp_pairp(sexp_cdr(ls2))
&& (sexp_litp(tmp) || ! sexp_pointerp(tmp) || sexp_refp(tmp)
|| sexp_lambdap(tmp))))
sexp_push(ctx, app, tmp);
}
if (sexp_pairp(app) && sexp_nullp(sexp_cdr(app)))
res = sexp_car(app);
else
sexp_seq_ls(res) = sexp_nreverse(ctx, app);
break;
}
sexp_gc_release5(ctx);
return res;
}
sexp sexp_simplify (sexp ctx, sexp self, sexp_sint_t n, sexp ast) {
return simplify(ctx, ast, SEXP_NULL, NULL);
}
static int usedp (sexp lambda, sexp var, sexp x) {
sexp ls;
loop:
switch (sexp_pointerp(x) ? sexp_pointer_tag(x) : 0) {
case SEXP_REF:
return sexp_ref_name(x) == var && sexp_ref_loc(x) == lambda;
case SEXP_SET:
x = sexp_set_value(x);
goto loop;
case SEXP_LAMBDA:
x = sexp_lambda_body(x);
goto loop;
case SEXP_CND:
if (usedp(lambda, var, sexp_cnd_test(x))
|| usedp(lambda, var, sexp_cnd_pass(x)))
return 1;
x = sexp_cnd_fail(x);
goto loop;
case SEXP_SEQ:
x = sexp_seq_ls(x);
case SEXP_PAIR:
for (ls=x; sexp_pairp(ls); ls=sexp_cdr(ls))
if (usedp(lambda, var, sexp_car(ls)))
return 1;
}
return 0;
}
int sexp_rest_unused_p (sexp lambda) {
sexp var;
for (var=sexp_lambda_params(lambda); sexp_pairp(var); var=sexp_cdr(var))
;
if (sexp_nullp(var)) return 0;
return !usedp(lambda, var, sexp_lambda_body(lambda));
}
#endif