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246
util/ego/ud/ud_const.c
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246
util/ego/ud/ud_const.c
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/* C O N S T A N T P R O P A G A T I O N */
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#include "../share/types.h"
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#include "../ud/ud.h"
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#include "../share/debug.h"
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#include "../share/global.h"
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#include "../share/alloc.h"
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#include "../share/lset.h"
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#include "../share/cset.h"
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#include "../share/def.h"
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#include "../share/aux.h"
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#include "../share/locals.h"
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#include "../../../h/em_mnem.h"
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#include "../../../h/em_pseu.h"
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#include "../../../h/em_spec.h"
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#include "../ud/ud_defs.h"
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#include "ud_const.h"
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#include "ud_aux.h"
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#define CHANGE_INDIR(p) (p->p_change->c_flags & CF_INDIR)
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#define IS_REG(v) (locals[TO_LOCAL(v)]->lc_flags & LCF_REG)
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#define BODY_KNOWN(p) (p->p_flags1 & (byte) PF_BODYSEEN)
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#define CALLS_UNKNOWN(p) (p->p_flags1 & (byte) PF_CALUNKNOWN)
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bool is_use(l)
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line_p l;
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{
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/* See if 'l' is a use of a variable */
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switch(INSTR(l)) {
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case op_lde:
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case op_ldl:
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case op_loe:
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case op_lol:
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return TRUE;
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default:
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return FALSE;
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}
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/* NOTREACHED */
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}
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bool value_known(def,val_out)
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line_p def;
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offset *val_out;
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{
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/* See if the value stored by definition 'def'
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* is known statically (i.e. is a constant).
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*/
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short sz1, sz2;
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offset v;
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line_p l;
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sz1 = ws;
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switch(INSTR(def)) {
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case op_inl:
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case op_ine:
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case op_del:
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case op_dee:
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return FALSE;
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case op_zrl:
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case op_zre:
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v = (offset) 0;
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break;
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case op_sdl:
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case op_sde:
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sz1 += ws;
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/* fall through ... */
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case op_stl:
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case op_ste:
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l = PREV(def);
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if (l == (line_p) 0) return FALSE;
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sz2 = ws;
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switch(INSTR(l)) {
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case op_zer:
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if (SHORT(l) >= sz1) {
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v = (offset) 0;
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break;
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}
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return FALSE;
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case op_ldc:
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sz2 += ws;
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/* fall through ...*/
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case op_loc:
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if (sz1 == sz2) {
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v = off_set(l);
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break;
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}
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/* fall through ... */
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default:
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return FALSE;
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}
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break;
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default:
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assert(FALSE);
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}
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*val_out = v;
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return TRUE;
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}
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bool affected(use,v,l)
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line_p use,l;
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short v;
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{
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/* See if the variable referenced by 'use' may be
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* changed by instruction l, which is either a cal, cai or
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* an indirect assignment.
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*/
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if (INSTR(l) == op_cal &&
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TYPE(use) == OPOBJECT &&
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BODY_KNOWN(PROC(l)) &&
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!CALLS_UNKNOWN(PROC(l)) &&
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!CHANGE_INDIR(PROC(l))) {
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return Cis_elem(OBJ(use)->o_id,PROC(l)->p_change->c_ext);
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}
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return TYPE(use) == OPOBJECT || !IS_REG(v);
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}
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STATIC search_backwards(use,v,found,def)
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line_p use, *def;
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short v;
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bool *found;
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{
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/* Search backwards in the current basic block,
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* starting at 'use', trying to find a definition
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* of the variable referenced by 'use', whose variable
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* number is v. If the definition found is an
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* implicit one, return 0 as def.
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*/
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register line_p l;
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for (l = PREV(use); l != (line_p) 0; l = PREV(l)) {
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if (does_expl_def(l) && same_var(use,l)) {
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*found = TRUE;
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*def = l;
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return;
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}
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if (does_impl_def(l) && affected(use,v,l)) {
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*found = TRUE;
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*def = (line_p) 0;
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return;
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}
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}
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*found = FALSE;
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}
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STATIC short outer_def(vdefs,in)
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cset vdefs, in;
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{
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/* See if there is a unique definition of variable
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* v reaching the beginning of block b.
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* 'vdefs' is vardefs[v], 'in' is IN(b).
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*/
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short n,defnr = 0;
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Cindex i;
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for (i = Cfirst(vdefs); i != (Cindex) 0; i = Cnext(i,vdefs)) {
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n = Celem(i);
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if (Cis_elem(EXPL_TO_DEFNR(n),in)) {
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if (defnr != 0) return 0;
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/* If there was already a def., there's no unique one */
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defnr = n;
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}
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}
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return defnr;
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}
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line_p unique_def(use,b,defnr_out)
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line_p use;
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bblock_p b;
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short *defnr_out;
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{
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/* See if there is one unique explicit definition
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* of the variable used by 'use', that reaches 'use'.
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*/
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short v;
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bool found;
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line_p def = (line_p) 0;
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*defnr_out = 0;
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var_nr(use,&v,&found);
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if (found) {
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/* We do maintain ud-info for this variable.
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* See if there is a previous explicit definition
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* in the current basic block.
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*/
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search_backwards(use,v,&found,&def);
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if (!found && !Cis_elem(IMPLICIT_DEF(v),IN(b))) {
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/* See if there is a unique explicit definition
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* outside the current block, reaching the
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* beginning of the current block.
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*/
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*defnr_out = outer_def(vardefs[v],IN(b));
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def = (*defnr_out == 0 ? (line_p) 0 : defs[*defnr_out]);
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}
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}
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return def;
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}
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fold_const(l,b,val)
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line_p l;
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bblock_p b;
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offset val;
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{
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/* Perform the substitutions required for constant folding */
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line_p n;
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n = int_line(val);
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switch(INSTR(l)) {
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case op_lol:
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case op_loe:
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n->l_instr = op_loc;
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break;
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case op_ldl:
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case op_lde:
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n->l_instr = op_ldc;
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break;
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default:
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assert (FALSE);
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}
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repl_line(l,n,b);
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}
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