4.1cBSD/usr/src/ucb/pascal/pdx/machine/nextaddr.c
/* Copyright (c) 1982 Regents of the University of California */
static char sccsid[] = "@(#)nextaddr.c 1.4 3/8/82";
/*
* Calculate the next address that will be executed from the current one.
*
* If the next address depends on runtime data (e.g. a conditional
* branch will depend on the value on top of the stack),
* we must execute up to the given address with "stepto".
*
* If the second argument is TRUE, we treat a CALL instruction as
* straight line rather than following it as a branch.
*/
#include "defs.h"
#include "machine.h"
#include "process.h"
#include "breakpoint.h"
#include "sym.h"
#include "pxops.h"
#include "optab.h"
#include "mappings.h"
#include "runtime.h"
#include "process/pxinfo.h"
#include "process/process.rep"
LOCAL ADDRESS docase(), dofor();
ADDRESS nextaddr(beginaddr, isnext)
ADDRESS beginaddr;
BOOLEAN isnext;
{
register PXOP op;
ADDRESS addr;
short offset;
int nextbyte;
SYM *s;
union {
short word;
char byte[2];
} o;
addr = beginaddr;
iread(&o.word, addr, sizeof(o.word));
op = (PXOP) o.byte[0];
nextbyte = o.byte[1];
addr += sizeof(short);
switch(op) {
# if (isvaxpx)
/*
* The version of px on the VAX assumes that the instruction
* at the entry point of a function is a TRA4 to the beginning
* of the block.
*/
# endif
case O_CALL: {
ADDRESS eaddr;
if (isnext) {
addr += sizeof(int);
} else {
# if (isvaxpx)
iread(&eaddr, addr, sizeof(eaddr));
addr = eaddr + sizeof(short);
iread(&addr, addr, sizeof(addr));
# else
iread(&offset, addr, sizeof(offset));
addr += offset;
# endif
stepto(addr);
if (linelookup(addr) == 0) {
bpact();
addr = pc;
}
if (ss_lines && trcond()) {
s = whatblock(addr);
if (s == NIL) {
panic("bad call addr");
}
printentry(s);
}
}
break;
}
# if (isvaxpx)
case O_FCALL: {
ADDRESS eaddr;
ADDRESS *fparam;
if (!isnext) {
stepto(addr - sizeof(short));
dread(&fparam, process->sp + sizeof(ADDRESS), sizeof(fparam));
dread(&eaddr, fparam, sizeof(eaddr));
addr = eaddr - ENDOFF;
stepto(addr);
if (linelookup(addr) == 0) {
bpact();
addr = pc;
}
if (ss_lines && trcond()) {
s = whatblock(addr);
if (s == NIL) {
panic("bad call addr");
}
printentry(s);
}
}
break;
}
# endif
case O_END:
if ((addr - sizeof(short)) == lastaddr()) {
stepto(addr - sizeof(short));
endprogram();
} else {
addr = return_addr();
s = whatblock(pc);
stepto(addr);
if (ss_lines && trcond()) {
printexit(s);
}
if (linelookup(addr) == 0) {
bpact();
addr = pc;
}
}
break;
# if (isvaxpx)
case O_TRA4:
case O_GOTO:
iread(&addr, addr, sizeof(addr));
break;
# endif
case O_TRA:
iread(&offset, addr, sizeof(offset));
addr += offset;
break;
case O_CON: {
short consize;
if (nextbyte == 0) {
iread(&consize, addr, sizeof(consize));
addr += sizeof(consize);
} else {
consize = nextbyte;
}
addr += consize;
break;
}
case O_CASE1OP:
addr = docase(nextbyte, 1, addr);
break;
case O_CASE2OP:
addr = docase(nextbyte, 2, addr);
break;
case O_CASE4OP:
addr = docase(nextbyte, 4, addr);
break;
case O_FOR1U:
addr = dofor(2, addr, nextbyte, 1);
break;
case O_FOR2U:
addr = dofor(2, addr, nextbyte, 1);
break;
case O_FOR4U:
addr = dofor(4, addr, nextbyte, 1);
break;
case O_FOR1D:
addr = dofor(2, addr, nextbyte, -1);
break;
case O_FOR2D:
addr = dofor(2, addr, nextbyte, -1);
break;
case O_FOR4D:
addr = dofor(4, addr, nextbyte, -1);
break;
case O_IF:
stepto(addr - sizeof(short));
dread(&offset, process->sp, sizeof(offset));
if (offset == 0) {
iread(&offset, addr, sizeof(offset));
addr += offset;
} else {
addr += sizeof(offset);
}
break;
default: {
# if (isvaxpx)
int i;
for (i = 0; optab[op].argtype[i] != 0; i++) {
switch(optab[op].argtype[i]) {
case ADDR4:
case LWORD:
addr += 4;
break;
case SUBOP:
break;
case ADDR2:
case HWORD:
case PSUBOP:
case DISP:
case VLEN:
if (i != 0 || nextbyte == 0) {
addr += sizeof(short);
}
break;
case STRING: {
char c;
while (nextbyte > 0) {
iread(&c, addr, 1);
if (c == '\0') {
break;
}
nextbyte--;
addr++;
}
addr++;
if ((addr&1) != 0) {
addr++;
}
break;
}
default:
panic("bad argtype");
/*NOTREACHED*/
}
}
# else
int oplen;
oplen = optab[op].nargs;
if (oplen < 0) {
oplen = (-oplen) - 1;
} else if (oplen > 0 && nextbyte != 0) {
oplen--;
}
oplen *= sizeof(int);
switch (op) {
case O_BEG:
case O_NODUMP:
oplen += 10;
break;
case O_CON:
oplen += ((nextbyte + 1)&~1);
break;
}
addr += oplen;
# endif
break;
}
}
return addr;
}
/*
* Find the next address that will be executed after the
* case statement at the given address.
*/
LOCAL ADDRESS docase(ncases, size, addr)
int ncases;
int size;
ADDRESS addr;
{
register ADDRESS i;
ADDRESS firstval, lastval, jmptable;
short offset;
long swtval, caseval;
stepto(addr - 2);
if (ncases == 0) {
iread(&ncases, addr, sizeof(ncases));
addr += sizeof(short);
}
jmptable = addr;
firstval = jmptable + ncases*sizeof(short);
lastval = firstval + ncases*size;
if (size <= 2) {
dread(&swtval, process->sp, 2);
} else {
dread(&swtval, process->sp, size);
}
for (i = firstval; i < lastval; i += size) {
iread(&caseval, i, size);
if (cmp(&swtval, &caseval, size) == 0) {
i = ((i - firstval) / size) * sizeof(offset);
iread(&offset, jmptable + i, sizeof(offset));
addr = jmptable + offset;
return addr;
}
}
return((lastval+1)&~1);
}
LOCAL ADDRESS dofor(size, addr, subop, incr)
int size;
ADDRESS addr;
short subop;
int incr;
{
register PROCESS *p;
long i, limit, lower;
ADDRESS valaddr;
short offset;
stepto(addr - sizeof(short));
p = process;
i = limit = 0;
if (subop == 0) {
addr += size;
}
dread(&valaddr, p->sp, sizeof(valaddr));
dread(&i, valaddr, size);
dread(&limit, p->sp + sizeof(valaddr), size);
i += (incr << (8*(sizeof(i) - size)));
addr += size;
/*
* It is very slow to go through the loop again and again.
* If it is desired to just skip to the end, the next 4 lines
* should be skipped.
*/
if ((incr > 0 && i < limit) || (incr < 0 && i > limit)) {
iread(&offset, addr, sizeof(offset));
return(addr + offset);
} else {
return(addr + sizeof(short));
}
}
/*
* Determine whether or not the given address corresponds to the
* end of a procedure.
*/
BOOLEAN isendofproc(addr)
ADDRESS addr;
{
PXOP op;
iread(&op, addr, sizeof(op));
return (op == O_END);
}