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Simulator: base_insn and insn in decode.c
- From: Ronald Hecht <ronald dot hecht at uni-rostock dot de>
- To: cgen at sourceware dot org
- Date: Mon, 31 Jul 2006 13:59:40 +0200
- Subject: Simulator: base_insn and insn in decode.c
Hello again,
i found another problem in decode. c. As I have variable instruction
size, decode.c does not handle base_insn and insn in the right way. The
file looks like this:
const IDESC *
proc8bf_decode (SIM_CPU *current_cpu, IADDR pc,
CGEN_INSN_INT base_insn, CGEN_INSN_INT entire_insn,
ARGBUF *abuf)
{
/* Result of decoder. */
PROC8BF_INSN_TYPE itype;
{
CGEN_INSN_INT insn = base_insn;
{
unsigned int val = (((insn >> 0) & (63 << 0)));
switch (val)
{
case 0 :
if ((entire_insn & 0xff) == 0x0)
{ itype = PROC8BF_INSN_NOP; goto extract_sfmt_nop; }
itype = PROC8BF_INSN_X_INVALID; goto extract_sfmt_empty;
case 1 :
if ((entire_insn & 0xff) == 0x1)
{ itype = PROC8BF_INSN_LDA; goto extract_sfmt_lda; }
itype = PROC8BF_INSN_X_INVALID; goto extract_sfmt_empty;
case 2 :
if ((entire_insn & 0xff) == 0x2)
{ itype = PROC8BF_INSN_LDC; goto extract_sfmt_ldc; }
itype = PROC8BF_INSN_X_INVALID; goto extract_sfmt_empty;
<snip>
I have given the first instruction byte as base_insn and entire_insn is
the complete instruction. The location of the base instruction depends
on the instruction size. So the calculation
unsigned int val = (((insn >> 0) & (63 << 0)));
is not correct. If I remove the if-statement around the goto
extract_sfmt_<insn> everything works correct. The simulatior does the
right things.
By the way: I found it a bit confusing to write mloop.in. It was
difficult to handle different size instructions. I did it this way:
xextract-pbb)
# Inputs: current_cpu, pc, sc, max_insns, FAST_P
# Outputs: sc, pc
# sc must be left pointing past the last created entry.
# pc must be left pointing past the last created entry.
# If the pbb is terminated by a cti insn, SET_CTI_VPC(sc) must be called
# to record the vpc of the cti insn.
# SET_INSN_COUNT(n) must be called to record number of real insns.
cat <<EOF
{
const IDESC *idesc;
int icount = 0;
while (max_insns > 0)
{
CGEN_INSN_INT insn;
CGEN_INSN_INT base_insn = GETIMEMUQI (current_cpu, pc);
idesc = @cpu@_decode(current_cpu, pc, base_insn, base_insn,
&sc->argbuf);
switch (idesc->length) {
case 1 : break;
case 2 :
insn = base_insn * 256 + GETIMEMUQI (current_cpu, pc + 1);
break;
case 3 :
insn = base_insn * 256 * 256 + GETIMEMUQI (current_cpu, pc + 1) *
256 + GETIMEMUQI (current_cpu, pc + 2);
break;
}
idesc = @cpu@_decode(current_cpu, pc, base_insn, insn, &sc->argbuf);
@cpu@_fill_argbuf (current_cpu, &sc->argbuf, idesc, pc, FAST_P);
if (! FAST_P) {
int trace_p = PC_IN_TRACE_RANGE_P (current_cpu, pc);
int profile_p = PC_IN_PROFILE_RANGE_P (current_cpu, pc);
@cpu@_fill_argbuf_tp (current_cpu, &sc->argbuf, trace_p, profile_p);
}
++sc;
--max_insns;
++icount;
pc += idesc->length;
if (IDESC_CTI_P (idesc))
{
SET_CTI_VPC (sc - 1);
break;
}
}
Finish:
SET_INSN_COUNT (icount);
}
EOF
;;
Is there an easier way to write this down?
Ronald