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bc: make long-running dc drop data it does not need (when it can)

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function                                             old     new   delta
zbc_vm_process                                       765     824     +59

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2018-12-22 19:23:46 +01:00
parent 5cf0b2d466
commit ec74a9c145
1 changed files with 34 additions and 15 deletions
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49
miscutils/bc.c
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@ -3437,11 +3437,11 @@ static BC_STATUS zdc_lex_token(BcLex *l)
// break;
case '\n':
// '\n' is BC_LEX_NLINE, not BC_LEX_WHITESPACE
// (and "case '\n'" is not just empty here)
// (and "case '\n':" is not just empty here)
// only to allow interactive dc have a way to exit
// "parse" stage of "parse,execute" loop
// on '\n', not on _next_ token (which would mean
// command are not executed on pressing <enter>).
// on <enter>, not on _next_ token (which would mean
// commands are not executed on pressing <enter>).
// IOW: typing "1p<enter>" should print "1" _at once_,
// not after some more input.
l->t.t = BC_LEX_NLINE;
@ -6673,6 +6673,9 @@ static BC_STATUS zbc_vm_process(const char *text)
if (s) RETURN_STATUS(s);
while (G.prs.l.t.t != BC_LEX_EOF) {
BcInstPtr *ip;
BcFunc *f;
dbg_lex("%s:%d G.prs.l.t.t:%d, parsing...", __func__, __LINE__, G.prs.l.t.t);
if (IS_BC) {
// FIXME: "eating" of stmt delimiters is coded inconsistently
@ -6695,6 +6698,15 @@ static BC_STATUS zbc_vm_process(const char *text)
bc_program_reset();
break;
}
ip = (void*)G.prog.exestack.v;
#if SANITY_CHECKS
if (G.prog.exestack.len != 1) // should have only main's IP
bb_error_msg_and_die("BUG:call stack");
if (ip->func != BC_PROG_MAIN)
bb_error_msg_and_die("BUG:not MAIN");
#endif
f = bc_program_func_BC_PROG_MAIN();
// bc discards strings, constants and code after each
// top-level statement in the "main program".
// This prevents "yes 1 | bc" from growing its memory
@ -6706,22 +6718,10 @@ static BC_STATUS zbc_vm_process(const char *text)
// but bc stores function strings/constants in per-function
// storage.
if (IS_BC) {
BcFunc *f;
BcInstPtr *ip = (void*)G.prog.exestack.v;
#if SANITY_CHECKS
if (G.prog.results.len != 0) // should be empty
bb_error_msg_and_die("BUG:data stack");
if (G.prog.exestack.len != 1) // should have only main's IP
bb_error_msg_and_die("BUG:call stack");
if (ip->func != BC_PROG_MAIN)
bb_error_msg_and_die("BUG:not MAIN");
#endif
//bb_error_msg("ip->func:%d >idx:%d >len:%d", ip->func, ip->inst_idx, ip->len);
f = bc_program_func_BC_PROG_MAIN();
//bb_error_msg("MAIN->code.len:%d >strs.len:%d >consts.len:%d", f->code.len, f->strs.len, f->consts.len); // labels, autos, nparams
bc_vec_pop_all(&f->code);
ip->inst_idx = 0;
IF_BC(bc_vec_pop_all(&f->strs);)
IF_BC(bc_vec_pop_all(&f->consts);)
} else {
@ -6731,7 +6731,26 @@ static BC_STATUS zbc_vm_process(const char *text)
s = zbc_lex_next(&G.prs.l);
if (s) RETURN_STATUS(s);
}
if (G.prog.results.len == 0
&& G.prog.vars.len == 0
) {
// If stack is empty and no registers exist (TODO: or they are all empty),
// we can get rid of accumulated strings and constants.
// In this example dc process should not grow
// its memory consumption with time:
// yes 1pc | dc
IF_DC(bc_vec_pop_all(&G.prog.strs);)
IF_DC(bc_vec_pop_all(&G.prog.consts);)
}
// The code is discarded always (below), thus this example
// should also not grow its memory consumption with time,
// even though its data stack is not empty:
// { echo 1; yes dk; } | dc
}
// We drop generated and executed code for both bc and dc:
bc_vec_pop_all(&f->code);
ip->inst_idx = 0;
}
dbg_lex_done("%s:%d done", __func__, __LINE__);