ref: 36af8405521be371605e4658ec8f4b133f3c7d6f
dir: /sys/src/cmd/7l/noop.c/
#include "l.h"
void
noops(void)
{
Prog *p, *q, *q1;
int o, aoffset, curframe, curbecome, maxbecome;
/*
* find leaf subroutines
* become sizes
* frame sizes
* strip NOPs
* expand RET
* expand BECOME pseudo
*/
if(debug['v'])
Bprint(&bso, "%5.2f noops\n", cputime());
Bflush(&bso);
curframe = 0;
curbecome = 0;
maxbecome = 0;
curtext = 0;
q = P;
for(p = firstp; p != P; p = p->link) {
/* find out how much arg space is used in this TEXT */
if(p->to.type == D_OREG && p->to.reg == REGSP)
if(p->to.offset > curframe)
curframe = p->to.offset;
switch(p->as) {
case ATEXT:
if(curtext && curtext->from.sym) {
curtext->from.sym->frame = curframe;
curtext->from.sym->become = curbecome;
if(curbecome > maxbecome)
maxbecome = curbecome;
}
curframe = 0;
curbecome = 0;
p->mark |= LEAF;
curtext = p;
break;
case ARETURN:
/* special form of RETURN is BECOME */
if(p->from.type == D_CONST)
if(p->from.offset > curbecome)
curbecome = p->from.offset;
break;
case ANOP:
q1 = p->link;
q->link = q1; /* q is non-nop */
q1->mark |= p->mark;
continue;
case ABL:
if(curtext != P)
curtext->mark &= ~LEAF;
case ACBNZ:
case ACBZ:
case ACBNZW:
case ACBZW:
case ATBZ:
case ATBNZ:
case ABCASE:
case AB:
case ABEQ:
case ABNE:
case ABCS:
case ABHS:
case ABCC:
case ABLO:
case ABMI:
case ABPL:
case ABVS:
case ABVC:
case ABHI:
case ABLS:
case ABGE:
case ABLT:
case ABGT:
case ABLE:
case AADR: /* strange */
case AADRP:
q1 = p->cond;
if(q1 != P) {
while(q1->as == ANOP) {
q1 = q1->link;
p->cond = q1;
}
}
break;
}
q = p;
}
if(curtext && curtext->from.sym) {
curtext->from.sym->frame = curframe;
curtext->from.sym->become = curbecome;
if(curbecome > maxbecome)
maxbecome = curbecome;
}
if(debug['b'])
print("max become = %d\n", maxbecome);
xdefine("ALEFbecome", STEXT, maxbecome);
curtext = 0;
for(p = firstp; p != P; p = p->link) {
switch(p->as) {
case ATEXT:
curtext = p;
break;
case ABL:
if(curtext != P && curtext->from.sym != S && curtext->to.offset >= 0) {
o = maxbecome - curtext->from.sym->frame;
if(o <= 0)
break;
/* calling a become or calling a variable */
if(p->to.sym == S || p->to.sym->become) {
curtext->to.offset += o;
if(debug['b']) {
curp = p;
print("%D calling %D increase %d\n",
&curtext->from, &p->to, o);
}
}
}
break;
}
}
for(p = firstp; p != P; p = p->link) {
o = p->as;
switch(o) {
case ATEXT:
curtext = p;
if(p->to.offset < 0)
autosize = 0;
else
autosize = p->to.offset + PCSZ;
if((curtext->mark & LEAF) && autosize <= PCSZ)
autosize = 0;
else if(autosize & (STACKALIGN-1))
autosize += STACKALIGN - (autosize&(STACKALIGN-1));
p->to.offset = autosize - PCSZ;
if(autosize == 0 && !(curtext->mark & LEAF)) {
if(debug['v'])
Bprint(&bso, "save suppressed in: %s\n",
curtext->from.sym->name);
Bflush(&bso);
curtext->mark |= LEAF;
}
aoffset = autosize;
if(aoffset > 0xF0)
aoffset = 0xF0;
if(curtext->mark & LEAF) {
if(curtext->from.sym)
curtext->from.sym->type = SLEAF;
if(autosize == 0)
break;
aoffset = 0;
}
q = p;
if(autosize > aoffset){
q = prg();
q->as = ASUB;
q->line = p->line;
q->from.type = D_CONST;
q->from.offset = autosize - aoffset;
q->to.type = D_REG;
q->to.reg = REGSP;
q->link = p->link;
p->link = q;
if(curtext->mark & LEAF)
break;
}
q1 = prg();
q1->as = AMOV;
q1->line = p->line;
q1->from.type = D_REG;
q1->from.reg = REGLINK;
q1->to.type = D_XPRE;
q1->to.offset = -aoffset;
q1->to.reg = REGSP;
q1->link = q->link;
q->link = q1;
break;
case ARETURN:
nocache(p);
if(p->from.type == D_CONST)
goto become;
if(curtext->mark & LEAF) {
if(autosize != 0){
p->as = AADD;
p->from.type = D_CONST;
p->from.offset = autosize;
p->to.type = D_REG;
p->to.reg = REGSP;
}
}else{
/* want write-back pre-indexed SP+autosize -> SP, loading REGLINK*/
aoffset = autosize;
if(aoffset > 0xF0)
aoffset = 0xF0;
p->as = AMOV;
p->from.type = D_XPOST;
p->from.offset = aoffset;
p->from.reg = REGSP;
p->to.type = D_REG;
p->to.reg = REGLINK;
if(autosize > aoffset) {
q = prg();
q->as = AADD;
q->from.type = D_CONST;
q->from.offset = autosize - aoffset;
q->to.type = D_REG;
q->to.reg = REGSP;
q->link = p->link;
p->link = q;
p = q;
}
}
if(p->as != ARETURN) {
q = prg();
q->line = p->line;
q->link = p->link;
p->link = q;
p = q;
}
p->as = ARET;
p->line = p->line;
p->to.type = D_OREG;
p->to.offset = 0;
p->to.reg = REGLINK;
break;
become:
if(curtext->mark & LEAF) {
if(!autosize) {
p->as = AB;
p->from = zprg.from;
break;
}
#ifdef optimise_time
q = prg();
q->line = p->line;
q->as = AB;
q->from = zprg.from;
q->to = p->to;
q->cond = p->cond;
q->link = p->link;
p->link = q;
p->as = AADD;
p->from = zprg.from;
p->from.type = D_CONST;
p->from.offset = autosize;
p->to = zprg.to;
p->to.type = D_REG;
p->to.reg = REGSP;
break;
#endif
}
q = prg();
q->line = p->line;
q->as = AB;
q->from = zprg.from;
q->to = p->to;
q->cond = p->cond;
q->link = p->link;
p->link = q;
p->as = AMOV;
p->from = zprg.from;
p->from.type = D_XPRE;
p->from.offset = -autosize;
p->from.reg = REGSP;
p->to = zprg.to;
p->to.type = D_REG;
p->to.reg = REGLINK;
break;
}
}
}
void
nocache(Prog *p)
{
p->optab = 0;
p->from.class = 0;
p->to.class = 0;
}