/* iterate basic block to find a dead register */
static reg_id_t
bb_find_dead_reg(instrlist_t *ilist)
{
instr_t *instr;
int i;
bool reg_is_read[DR_NUM_GPR_REGS] = { false,};
for (instr = instrlist_first(ilist);
instr != NULL;
instr = instr_get_next(instr)) {
if (instr_is_syscall(instr) || instr_is_interrupt(instr))
return DR_REG_NULL;
for (i = 0; i < DR_NUM_GPR_REGS; i++) {
if (!reg_is_read[i] &&
instr_reads_from_reg(instr, (reg_id_t)(DR_REG_START_GPR + i))) {
reg_is_read[i] = true;
}
if (!reg_is_read[i] &&
instr_writes_to_exact_reg(instr,
(reg_id_t)(DR_REG_START_GPR + i))) {
return (reg_id_t)(DR_REG_START_GPR + i);
}
#ifdef X64
/* in x64, update on 32-bit register kills the whole register */
if (!reg_is_read[i] &&
instr_writes_to_exact_reg(instr,
reg_64_to_32
((reg_id_t)(DR_REG_START_GPR + i)))) {
return (reg_id_t)(DR_REG_START_GPR + i);
}
#endif
}
}
return DR_REG_NULL;
}
DR_EXPORT
bool
drx_aflags_are_dead(instr_t *where)
{
instr_t *instr;
uint flags;
for (instr = where; instr != NULL; instr = instr_get_next(instr)) {
/* we treat syscall/interrupt as aflags read */
if (instr_is_syscall(instr) || instr_is_interrupt(instr))
return false;
flags = instr_get_arith_flags(instr, DR_QUERY_DEFAULT);
if (TESTANY(EFLAGS_READ_ARITH, flags))
return false;
if (TESTALL(EFLAGS_WRITE_ARITH, flags))
return true;
if (instr_is_cti(instr)) {
if (instr_is_app(instr) &&
(instr_is_ubr(instr) || instr_is_call_direct(instr))) {
instr_t *next = instr_get_next(instr);
opnd_t tgt = instr_get_target(instr);
/* continue on elision */
if (next != NULL && instr_is_app(next) &&
opnd_is_pc(tgt) &&
opnd_get_pc(tgt) == instr_get_app_pc(next))
continue;
}
/* unknown target, assume aflags is live */
return false;
}
}
return false;
}
