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gother.c
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gother.c
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// Copyright (C) 1986-1998 by Symantec
// Copyright (C) 2000-2015 by Digital Mars
// All Rights Reserved
// http://www.digitalmars.com
// Written by Walter Bright
/*
* This source file is made available for personal use
* only. The license is in backendlicense.txt
* For any other uses, please contact Digital Mars.
*/
#if (SCPP || MARS) && !HTOD
#include <stdio.h>
#include <time.h>
#include "cc.h"
#include "global.h"
#include "el.h"
#include "go.h"
#include "oper.h"
#include "list.h"
#include "type.h"
#if SCPP
#include "parser.h"
#endif
static char __file__[] = __FILE__; /* for tassert.h */
#include "tassert.h"
extern void warning(const char *filename, unsigned linnum, unsigned charnum, const char *format, ...);
STATIC void rd_free_elem(elem *e);
STATIC void rd_compute();
STATIC void conpropwalk(elem *n , vec_t IN);
STATIC void chkrd(elem *n , list_t rdlist);
STATIC elem * chkprop(elem *n , list_t rdlist);
STATIC void arrayboundsrds(void);
STATIC void eqeqranges(void);
STATIC void intranges(void);
STATIC int loopcheck(block *start , block *inc , block *rel);
STATIC void cpwalk(elem *n , vec_t IN);
STATIC unsigned numasg(elem *e);
STATIC void accumda(elem *n , vec_t DEAD , vec_t POSS);
STATIC void dvwalk(elem *n , unsigned i);
STATIC int killed(unsigned j , block *bp , block *b);
STATIC int ispath(unsigned j , block *bp , block *b);
/**********************************************************************/
// Lists to help identify ranges of variables
struct Elemdata
{ Elemdata *next; // linked list
elem *pelem; // the elem in question
block *pblock; // which block it's in
list_t rdlist; // list of definition elems for *pelem
static Elemdata *ctor(elem *e,block *b,list_t rd);
};
Elemdata *Elemdata::ctor(elem *e,block *b,list_t rd)
{ Elemdata *ed;
ed = (Elemdata *) MEM_BEF_CALLOC(sizeof(Elemdata));
ed->pelem = e;
ed->pblock = b;
ed->rdlist = rd;
return ed;
}
/*****************
* Free list of Elemdata's.
*/
STATIC void elemdatafree(Elemdata **plist)
{ Elemdata *el;
Elemdata *eln;
for (el = *plist; el; el = eln)
{ eln = el->next;
list_free(&el->rdlist);
MEM_BEF_FREE(el);
}
*plist = NULL;
}
static Elemdata *eqeqlist = NULL; // list of Elemdata's of OPeqeq & OPne elems
static Elemdata *rellist = NULL; // list of Elemdata's of relop elems
static Elemdata *inclist = NULL; // list of Elemdata's of increment elems
/*************************** Constant Propagation ***************************/
/**************************
* Constant propagation.
* Also detects use of variable before any possible def.
*/
void constprop()
{
rd_compute();
intranges(); // compute integer ranges
//eqeqranges(); // see if we can eliminate some relationals
elemdatafree(&eqeqlist);
elemdatafree(&rellist);
elemdatafree(&inclist);
}
/************************************
* Compute reaching definitions.
* Note: RD vectors are destroyed by this.
*/
static block *thisblock;
STATIC void rd_compute()
{ unsigned i;
cmes("constprop()\n");
assert(dfo);
flowrd(); /* compute reaching definitions (rd) */
if (go.deftop == 0) /* if no reaching defs */
return;
assert(rellist == NULL && inclist == NULL && eqeqlist == NULL);
block_clearvisit();
for (i = 0; i < dfotop; i++) /* for each block */
{ block *b = dfo[i];
switch (b->BC)
{
case BCjcatch:
case BC_finally:
case BC_lpad:
case BCasm:
case BCcatch:
block_visit(b);
break;
}
}
for (i = 0; i < dfotop; i++) /* for each block */
{ block *b;
b = dfo[i];
thisblock = b;
#if 0
dbg_printf("block %d Bin ",i); vec_println(b->Binrd);
dbg_printf(" Bout "); vec_println(b->Boutrd);
#endif
if (b->Bflags & BFLvisited)
continue; // not reliable for this block
if (b->Belem)
{
conpropwalk(b->Belem,b->Binrd);
#ifdef DEBUG
if (!(vec_equal(b->Binrd,b->Boutrd)))
{ int j;
dbg_printf("block %d Binrd ",i); vec_println(b->Binrd);
dbg_printf(" Boutrd "); vec_println(b->Boutrd);
WReqn(b->Belem);
dbg_printf("\n");
vec_xorass(b->Binrd,b->Boutrd);
j = vec_index(0,b->Binrd);
WReqn(go.defnod[j].DNelem);
dbg_printf("\n");
}
#endif
assert(vec_equal(b->Binrd,b->Boutrd));
}
}
}
/***************************
* Support routine for constprop().
* Visit each elem in order
* If elem is a reference to a variable, and
* all the reaching defs of that variable are
* defining it to be a specific constant,
* Replace reference with that constant.
* Generate warning if no reaching defs for a
* variable, and the variable is on the stack
* or in a register.
* If elem is an assignment or function call or OPasm
* Modify vector of reaching defs.
*/
STATIC void conpropwalk(elem *n,vec_t IN)
{ unsigned op;
Elemdata *pdata;
vec_t L,R;
elem *t;
assert(n && IN);
/*chkvecdim(go.deftop,0);*/
//printf("conpropwalk()\n"),elem_print(n);
op = n->Eoper;
if (op == OPcolon || op == OPcolon2)
{ L = vec_clone(IN);
conpropwalk(n->E1,L);
conpropwalk(n->E2,IN);
vec_orass(IN,L); /* IN = L | R */
vec_free(L);
}
else if (op == OPandand || op == OPoror)
{ conpropwalk(n->E1,IN);
R = vec_clone(IN);
conpropwalk(n->E2,R);
vec_orass(IN,R); /* IN |= R */
vec_free(R);
}
else if (OTunary(op))
goto L3;
else if (ERTOL(n))
{ conpropwalk(n->E2,IN);
L3:
t = n->E1;
if (OTassign(op))
{
if (t->Eoper == OPvar)
{
// Note that the following ignores OPnegass
if (OTopeq(op) && sytab[t->EV.sp.Vsym->Sclass] & SCRD)
{ elem *e;
list_t rdl;
rdl = listrds(IN,t,NULL);
if (!(config.flags & CFGnowarning)) // if warnings are enabled
chkrd(t,rdl);
e = chkprop(t,rdl);
if (e)
{ // Replace (t op= exp) with (t = e op exp)
e = el_copytree(e);
e->Ety = t->Ety;
n->E2 = el_bin(opeqtoop(op),n->Ety,e,n->E2);
n->Eoper = OPeq;
}
list_free(&rdl);
}
}
else
conpropwalk(t,IN);
}
else
conpropwalk(t,IN);
}
else if (OTbinary(op))
{
if (OTassign(op))
{ t = Elvalue(n);
if (t->Eoper != OPvar)
conpropwalk(t,IN);
}
else
conpropwalk(n->E1,IN);
conpropwalk(n->E2,IN);
}
// Collect data for subsequent optimizations
if (OTbinary(op) && n->E1->Eoper == OPvar && n->E2->Eoper == OPconst)
{
switch (op)
{
case OPlt:
case OPgt:
case OPle:
case OPge:
// Collect compare elems and their rd's in the rellist list
if (tyintegral(n->E1->Ety) &&
tyintegral(n->E2->Ety)
)
{
//dbg_printf("appending to rellist\n"); elem_print(n);
pdata = Elemdata::ctor(n,thisblock,listrds(IN,n->E1,NULL));
pdata->next = rellist;
rellist = pdata;
}
break;
case OPaddass:
case OPminass:
case OPpostinc:
case OPpostdec:
// Collect increment elems and their rd's in the inclist list
if (tyintegral(n->E1->Ety))
{
//dbg_printf("appending to inclist\n"); elem_print(n);
pdata = Elemdata::ctor(n,thisblock,listrds(IN,n->E1,NULL));
pdata->next = inclist;
inclist = pdata;
}
break;
case OPne:
case OPeqeq:
// Collect compare elems and their rd's in the rellist list
if (tyintegral(n->E1->Ety))
{ //dbg_printf("appending to eqeqlist\n"); elem_print(n);
pdata = Elemdata::ctor(n,thisblock,listrds(IN,n->E1,NULL));
pdata->next = eqeqlist;
eqeqlist = pdata;
}
break;
}
}
if (OTdef(op)) /* if definition elem */
updaterd(n,IN,NULL); /* then update IN vector */
/* now we get to the part that checks to see if we can */
/* propagate a constant. */
if (op == OPvar && sytab[n->EV.sp.Vsym->Sclass] & SCRD)
{ list_t rdl;
//printf("const prop: %s\n", n->EV.sp.Vsym->Sident);
rdl = listrds(IN,n,NULL);
if (!(config.flags & CFGnowarning)) // if warnings are enabled
chkrd(n,rdl);
elem *e = chkprop(n,rdl);
if (e)
{ tym_t nty;
nty = n->Ety;
el_copy(n,e);
n->Ety = nty; // retain original type
}
list_free(&rdl);
}
}
/******************************
* Give error if there are no reaching defs for variable v.
*/
STATIC void chkrd(elem *n,list_t rdlist)
{ unsigned i;
symbol *sv;
int unambig;
sv = n->EV.sp.Vsym;
assert(sytab[sv->Sclass] & SCRD);
if (sv->Sflags & SFLnord) // if already printed a warning
return;
if (sv->ty() & mTYvolatile)
return;
unambig = sv->Sflags & SFLunambig;
for (list_t l = rdlist; l; l = list_next(l))
{ elem *d = (elem *) list_ptr(l);
elem_debug(d);
if (d->Eoper == OPasm) /* OPasm elems ruin everything */
return;
if (OTassign(d->Eoper))
{
if (d->E1->Eoper == OPvar)
{ if (d->E1->EV.sp.Vsym == sv)
return;
}
else if (!unambig)
return;
}
else
{ if (!unambig)
return;
}
}
// If there are any asm blocks, don't print the message
for (i = 0; i < dfotop; i++)
if (dfo[i]->BC == BCasm)
return;
// If variable contains bit fields, don't print message (because if
// bit field is the first set, then we get a spurious warning).
// STL uses 0 sized structs to transmit type information, so
// don't complain about them being used before set.
if (type_struct(sv->Stype))
{
if (sv->Stype->Ttag->Sstruct->Sflags & (STRbitfields | STR0size))
return;
}
#if 0
// If variable is zero length static array, don't print message.
// BUG: Suppress error even if variable is initialized with void.
if (sv->Stype->Tty == TYarray && sv->Stype->Tdim == 0)
{
printf("sv->Sident = %s\n", sv->Sident);
return;
}
#endif
#if SCPP
{ Outbuffer buf;
char *p2;
type_tostring(&buf, sv->Stype);
buf.writeByte(' ');
buf.write(sv->Sident);
p2 = buf.toString();
warerr(WM_used_b4_set, p2); // variable used before set
}
#endif
#if MARS
/* Watch out for:
void test()
{
void[0] x;
auto y = x;
}
*/
if (type_size(sv->Stype) != 0)
{
warning(n->Esrcpos.Sfilename, n->Esrcpos.Slinnum, n->Esrcpos.Scharnum,
"variable %s used before set", sv->Sident);
}
#endif
sv->Sflags |= SFLnord; // no redundant messages
//elem_print(n);
}
/**********************************
* Look through the vector of reaching defs (IN) to see
* if all defs of n are of the same constant. If so, replace
* n with that constant.
* Bit fields are gross, so don't propagate anything with assignments
* to a bit field.
* Note the flaw in the reaching def vector. There is currently no way
* to detect RDs from when the function is invoked, i.e. RDs for parameters,
* statics and globals. This could be fixed by adding dummy defs for
* them before startblock, but we just kludge it and don't propagate
* stuff for them.
* Returns:
* NULL do not propagate constant
* e constant elem that we should replace n with
*/
STATIC elem * chkprop(elem *n,list_t rdlist)
{
elem *foundelem = NULL;
int unambig;
symbol *sv;
tym_t nty;
unsigned nsize;
targ_size_t noff;
list_t l;
//printf("checkprop: "); WReqn(n); printf("\n");
assert(n && n->Eoper == OPvar);
elem_debug(n);
sv = n->EV.sp.Vsym;
assert(sytab[sv->Sclass] & SCRD);
nty = n->Ety;
if (!tyscalar(nty))
goto noprop;
nsize = size(nty);
noff = n->EV.sp.Voffset;
unambig = sv->Sflags & SFLunambig;
for (l = rdlist; l; l = list_next(l))
{ elem *d = (elem *) list_ptr(l);
elem_debug(d);
//printf("\trd: "); WReqn(d); printf("\n");
if (d->Eoper == OPasm) /* OPasm elems ruin everything */
goto noprop;
// Runs afoul of Buzilla 4506
/*if (OTassign(d->Eoper) && EBIN(d))*/ // if assignment elem
if (OTassign(d->Eoper)) // if assignment elem
{ elem *t = Elvalue(d);
if (t->Eoper == OPvar)
{ assert(t->EV.sp.Vsym == sv);
if (d->Eoper == OPstreq ||
!tyscalar(t->Ety))
goto noprop; // not worth bothering with these cases
if (d->Eoper == OPnegass)
goto noprop; // don't bother with this case, either
/* Everything must match or we must skip this variable */
/* (in case of assigning to overlapping unions, etc.) */
if (t->EV.sp.Voffset != noff ||
/* If sizes match, we are ok */
size(t->Ety) != nsize &&
!(d->E2->Eoper == OPconst && size(t->Ety) > nsize && !tyfloating(d->E2->Ety)))
goto noprop;
}
else
{ if (unambig) /* unambiguous assignments only */
continue;
goto noprop;
}
if (d->Eoper != OPeq)
goto noprop;
}
else /* must be a call elem */
{
if (unambig)
continue;
else
goto noprop; /* could be affected */
}
if (d->E2->Eoper == OPconst || d->E2->Eoper == OPrelconst)
{
if (foundelem) /* already found one */
{ /* then they must be the same */
if (!el_match(foundelem,d->E2))
goto noprop;
}
else /* else this is it */
foundelem = d->E2;
}
else
goto noprop;
}
if (foundelem) /* if we got one */
{ /* replace n with foundelem */
#ifdef DEBUG
if (debugc)
{ dbg_printf("const prop (");
WReqn(n);
dbg_printf(" replaced by ");
WReqn(foundelem);
dbg_printf("), %p to %p\n",foundelem,n);
}
#endif
go.changes++;
return foundelem;
}
noprop:
return NULL;
}
/***********************************
* Find all the reaching defs of OPvar e.
* Put into a linked list, or just set the RD bits in a vector.
*
*/
list_t listrds(vec_t IN,elem *e,vec_t f)
{
unsigned i;
unsigned unambig;
Symbol *s;
unsigned nsize;
targ_size_t noff;
tym_t ty;
//printf("listrds: "); WReqn(e); printf("\n");
assert(IN);
list_t rdlist = NULL;
assert(e->Eoper == OPvar);
s = e->EV.sp.Vsym;
ty = e->Ety;
if (tyscalar(ty))
nsize = size(ty);
noff = e->EV.sp.Voffset;
unambig = s->Sflags & SFLunambig;
if (f)
vec_clear(f);
foreach (i, go.deftop, IN)
{
elem *d = go.defnod[i].DNelem;
//dbg_printf("\tlooking at "); WReqn(d); dbg_printf("\n");
unsigned op = d->Eoper;
if (op == OPasm) // assume ASM elems define everything
goto listit;
if (OTassign(op))
{ elem *t = Elvalue(d);
if (t->Eoper == OPvar && t->EV.sp.Vsym == s)
{ if (op == OPstreq)
goto listit;
if (!tyscalar(ty) || !tyscalar(t->Ety))
goto listit;
// If t does not overlap e, then it doesn't affect things
if (noff + nsize > t->EV.sp.Voffset &&
t->EV.sp.Voffset + size(t->Ety) > noff)
goto listit; // it's an assignment to s
}
else if (t->Eoper != OPvar && !unambig)
goto listit; /* assignment through pointer */
}
else if (!unambig)
goto listit; /* probably a function call */
continue;
listit:
//dbg_printf("\tlisting "); WReqn(d); dbg_printf("\n");
if (f)
vec_setbit(i,f);
else
list_prepend(&rdlist,d); // add the definition node
}
return rdlist;
}
/********************************************
* Look at reaching defs for expressions of the form (v == c) and (v != c).
* If all definitions of v are c or are not c, then we can replace the
* expression with 1 or 0.
*/
STATIC void eqeqranges()
{ Elemdata *rel;
list_t rdl;
Symbol *v;
int sz;
elem *e;
targ_llong c;
int result;
for (rel = eqeqlist; rel; rel = rel->next)
{
e = rel->pelem;
v = e->E1->EV.sp.Vsym;
if (!(sytab[v->Sclass] & SCRD))
continue;
sz = tysize(e->E1->Ety);
c = el_tolong(e->E2);
result = -1; // result not known yet
for (rdl = rel->rdlist; rdl; rdl = list_next(rdl))
{ elem *erd = (elem *) list_ptr(rdl);
elem *erd1;
int szrd;
int tmp;
elem_debug(erd);
if (erd->Eoper != OPeq ||
(erd1 = erd->E1)->Eoper != OPvar ||
erd->E2->Eoper != OPconst
)
goto L1;
szrd = tysize(erd1->Ety);
if (erd1->EV.sp.Voffset + szrd <= e->E1->EV.sp.Voffset ||
e->E1->EV.sp.Voffset + sz <= erd1->EV.sp.Voffset)
continue; // doesn't affect us, skip it
if (szrd != sz || e->E1->EV.sp.Voffset != erd1->EV.sp.Voffset)
goto L1; // overlapping - forget it
tmp = (c == el_tolong(erd->E2));
if (result == -1)
result = tmp;
else if (result != tmp)
goto L1;
}
if (result >= 0)
{
//printf("replacing with %d\n",result);
el_free(e->E1);
el_free(e->E2);
e->EV.Vint = (e->Eoper == OPeqeq) ? result : result ^ 1;
e->Eoper = OPconst;
}
L1: ;
}
}
/******************************
* Examine rellist and inclist to determine if any of the signed compare
* elems in rellist can be replace by unsigned compares.
* rellist is list of relationals in function.
* inclist is list of increment elems in function.
*/
STATIC void intranges()
{ Elemdata *rel,*iel;
block *rb,*ib;
symbol *v;
elem *rdeq,*rdinc;
unsigned incop,relatop;
targ_int initial,increment,final;
cmes("intranges()\n");
for (rel = rellist; rel; rel = rel->next)
{
rb = rel->pblock;
//dbg_printf("rel->pelem: "); WReqn(rel->pelem); dbg_printf("\n");
assert(rel->pelem->E1->Eoper == OPvar);
v = rel->pelem->E1->EV.sp.Vsym;
// RD info is only reliable for registers and autos
if (!(sytab[v->Sclass] & SCRD))
continue;
/* Look for two rd's: an = and an increment */
if (list_nitems(rel->rdlist) != 2)
continue;
rdeq = list_elem(list_next(rel->rdlist));
if (rdeq->Eoper != OPeq)
{ rdinc = rdeq;
rdeq = list_elem(rel->rdlist);
if (rdeq->Eoper != OPeq)
continue;
}
else
rdinc = list_elem(rel->rdlist);
#if 0
printf("\neq: "); WReqn(rdeq); printf("\n");
printf("rel: "); WReqn(rel->pelem); printf("\n");
printf("inc: "); WReqn(rdinc); printf("\n");
#endif
incop = rdinc->Eoper;
if (!OTpost(incop) && incop != OPaddass && incop != OPminass)
continue;
/* lvalues should be unambiguous defs */
if (rdeq->E1->Eoper != OPvar || rdinc->E1->Eoper != OPvar)
continue;
/* rvalues should be constants */
if (rdeq->E2->Eoper != OPconst || rdinc->E2->Eoper != OPconst)
continue;
/* Ensure that the only defs reaching the increment elem (rdinc) */
/* are rdeq and rdinc. */
for (iel = inclist; TRUE; iel = iel->next)
{ elem *rd1,*rd2;
if (!iel)
goto nextrel;
ib = iel->pblock;
if (iel->pelem != rdinc)
continue; /* not our increment elem */
if (list_nitems(iel->rdlist) != 2)
{ //printf("!= 2\n");
goto nextrel;
}
rd1 = list_elem(iel->rdlist);
rd2 = list_elem(list_next(iel->rdlist));
/* The rd's for the relational elem (rdeq,rdinc) must be */
/* the same as the rd's for tne increment elem (rd1,rd2). */
if (rd1 == rdeq && rd2 == rdinc || rd1 == rdinc && rd2 == rdeq)
break;
}
// Check that all paths from rdinc to rdinc must pass through rdrel
{ int i;
// ib: block of increment
// rb: block of relational
i = loopcheck(ib,ib,rb);
block_clearvisit();
if (i)
continue;
}
/* Gather initial, increment, and final values for loop */
initial = el_tolong(rdeq->E2);
increment = el_tolong(rdinc->E2);
if (incop == OPpostdec || incop == OPminass)
increment = -increment;
relatop = rel->pelem->Eoper;
final = el_tolong(rel->pelem->E2);
//printf("initial = %d, increment = %d, final = %d\n",initial,increment,final);
/* Determine if we can make the relational an unsigned */
if (initial >= 0)
{ if (final >= initial)
{ if (increment > 0 && ((final - initial) % increment) == 0)
goto makeuns;
}
else if (final >= 0)
{ /* 0 <= final < initial */
if (increment < 0 && ((final - initial) % increment) == 0 &&
!(final + increment < 0 &&
(relatop == OPge || relatop == OPlt)
)
)
{
makeuns:
if (!tyuns(rel->pelem->E2->Ety))
{
rel->pelem->E2->Ety = touns(rel->pelem->E2->Ety);
rel->pelem->Nflags |= NFLtouns;
#ifdef DEBUG
if (debugc)
{ WReqn(rel->pelem);
printf(" made unsigned, initial = %ld, increment = %ld,\
final = %ld\n",(long int)initial,(long int)increment,(long int)final);
}
#endif
go.changes++;
}
#if 0
// Eliminate loop if it is empty
if (relatop == OPlt &&
rb->BC == BCiftrue &&
list_block(rb->Bsucc) == rb &&
rb->Belem->Eoper == OPcomma &&
rb->Belem->E1 == rdinc &&
rb->Belem->E2 == rel->pelem
)
{
rel->pelem->Eoper = OPeq;
rel->pelem->Ety = rel->pelem->E1->Ety;
rb->BC = BCgoto;
list_subtract(&rb->Bsucc,rb);
list_subtract(&rb->Bpred,rb);
#ifdef DEBUG
if (debugc)
{ WReqn(rel->pelem);
dbg_printf(" eliminated loop\n");
}
#endif
go.changes++;
}
#endif
}
}
}
nextrel:
;
}
}
/***********************
* Return TRUE if there is a path from start to inc without
* passing through rel.
*/
STATIC int loopcheck(block *start,block *inc,block *rel)
{ list_t list;
block *b;
if (!(start->Bflags & BFLvisited))
{ start->Bflags |= BFLvisited; /* guarantee eventual termination */
for (list = start->Bsucc; list; list = list_next(list))
{ b = (block *) list_ptr(list);
if (b != rel && (b == inc || loopcheck(b,inc,rel)))
return TRUE;
}
}
return FALSE;
}
/****************************
* Do copy propagation.
* Copy propagation elems are of the form OPvar=OPvar, and they are
* in go.expnod[].
*/
static int recalc;
void copyprop()
{ unsigned i;
out_regcand(&globsym);
cmes("copyprop()\n");
assert(dfo);
Lagain:
flowcp(); /* compute available copy statements */
if (go.exptop <= 1)
return; /* none available */
#if 0
for (i = 1; i < go.exptop; i++)
{ dbg_printf("go.expnod[%d] = (",i);
WReqn(go.expnod[i]);
dbg_printf(");\n");
}
#endif
recalc = 0;
for (i = 0; i < dfotop; i++) /* for each block */
{ block *b;
b = dfo[i];
if (b->Belem)
{
#if 0
dbg_printf("B%d, elem (",i);
WReqn(b->Belem); dbg_printf(")\nBin ");
vec_println(b->Bin);
cpwalk(b->Belem,b->Bin);
dbg_printf("Bino ");
vec_println(b->Bin);
dbg_printf("Bout ");
vec_println(b->Bout);
#else
cpwalk(b->Belem,b->Bin);
#endif
/*assert(vec_equal(b->Bin,b->Bout)); */
/* The previous assert() is correct except */
/* for the following case: */
/* a=b; d=a; a=b; */
/* The vectors don't match because the */
/* equations changed to: */
/* a=b; d=b; a=b; */
/* and the d=b copy elem now reaches the end */
/* of the block (the d=a elem didn't). */
}
if (recalc)
goto Lagain;
}
}
/*****************************
* Walk tree n, doing copy propagation as we go.
* Keep IN up to date.
*/
STATIC void cpwalk(elem *n,vec_t IN)
{ unsigned op,i;
elem *t;
vec_t L;
static int nocp;
assert(n && IN);
/*chkvecdim(go.exptop,0);*/
if (recalc)
return;
op = n->Eoper;
if (op == OPcolon || op == OPcolon2)
{
L = vec_clone(IN);
cpwalk(n->E1,L);
cpwalk(n->E2,IN);
vec_andass(IN,L); // IN = L & R
vec_free(L);
}
else if (op == OPandand || op == OPoror)
{ cpwalk(n->E1,IN);
L = vec_clone(IN);
cpwalk(n->E2,L);
vec_andass(IN,L); // IN = L & R
vec_free(L);
}
else if (OTunary(op))
{
t = n->E1;
if (OTassign(op))
{ if (t->Eoper == OPind)
cpwalk(t->E1,IN);
}
else if (op == OPctor || op == OPdtor)
{
/* This kludge is necessary because in except_pop()
* an el_match is done on the lvalue. If copy propagation
* changes the OPctor but not the corresponding OPdtor,
* then the match won't happen and except_pop()
* will fail.
*/
nocp++;
cpwalk(t,IN);
nocp--;
}
else
cpwalk(t,IN);
}
else if (OTassign(op))
{ cpwalk(n->E2,IN);
t = Elvalue(n);
if (t->Eoper == OPind)
cpwalk(t,IN);
else
{
#ifdef DEBUG
if (t->Eoper != OPvar) elem_print(n);
#endif
assert(t->Eoper == OPvar);
}
}
else if (ERTOL(n))
{ cpwalk(n->E2,IN);
cpwalk(n->E1,IN);
}
else if (OTbinary(op))
{
cpwalk(n->E1,IN);
cpwalk(n->E2,IN);
}
if (OTdef(op)) // if definition elem
{ int ambig; /* TRUE if ambiguous def */
ambig = !OTassign(op) || t->Eoper == OPind;
foreach (i,go.exptop,IN) /* for each active copy elem */
{ symbol *v;
if (op == OPasm)
goto clr;
/* If this elem could kill the lvalue or the rvalue, */
/* Clear bit in IN. */
v = go.expnod[i]->E1->EV.sp.Vsym;
if (ambig)
{ if (!(v->Sflags & SFLunambig))
goto clr;
}