On 05/29/2012 03:03 AM, Steven Bosscher wrote:
Hello,
In gcse.c:insert_insn_end_basic_block() I found the following code:
#ifdef HAVE_cc0
/* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts
if cc0 isn't set. */
note = find_reg_note (insn, REG_CC_SETTER, NULL_RTX);
if (note)
insn = XEXP (note, 0);
else
{
rtx maybe_cc0_setter = prev_nonnote_insn (insn);
if (maybe_cc0_setter
&& INSN_P (maybe_cc0_setter)
&& sets_cc0_p (PATTERN (maybe_cc0_setter)))
insn = maybe_cc0_setter;
}
#endif
How can this work? As far as grep understands, only link_cc0_insns
creates REG_CC_SETTER notes, but that function is only called from
reorg.c (and even then, only if it makes a transformation). So NOTE
will always be NULL.
Are REG_CC_SETTER/REG_CC_USER notes supposed to exist before dbr_sched?
Well, we're talking about code that is 14 years old... I really don't
remember.
P.S. The code goes on to use prev_nonnote_insn, which may cross basic
block boundaries, so prev_nonnote_insn_bb should be used instead.
On a cc0 target, this is not true.
jeff
