Hi all,
In PR51505(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51505), Paolo Bonzini
added the code to delete REG_EQUAL notes in df_remove_dead_eq_notes:
gcc/df-problems.c:
df_remove_dead_eq_notes (rtx_insn *insn, bitmap live)
{
...
case REG_EQUAL:
case REG_EQUIV:
{
/* Remove the notes that refer to dead registers. As we have at
most
one REG_EQUAL/EQUIV note, all of EQ_USES will refer to this note
so we need to purge the complete EQ_USES vector when removing
the note using df_notes_rescan. */
df_ref use;
bool deleted = false;
FOR_EACH_INSN_EQ_USE (use, insn)
if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER
&& DF_REF_LOC (use)
&& (DF_REF_FLAGS (use) & DF_REF_IN_NOTE)
&& !bitmap_bit_p (live, DF_REF_REGNO (use))
&& loc_mentioned_in_p (DF_REF_LOC (use), XEXP (link, 0)))
{
deleted = true;
break;
}
if (deleted)
{
rtx next;
if (REG_DEAD_DEBUGGING)
df_print_note ("deleting: ", insn, link);
next = XEXP (link, 1);
free_EXPR_LIST_node (link);
*pprev = link = next;
df_notes_rescan (insn);
}
...
}
while I have a test case as below:
typedef long myint_t;
__attribute__ ((noinline)) myint_t
hash_loop (myint_t nblocks, myint_t hash)
{
int i;
for (i = 0; i < nblocks; i++)
hash = ((hash + 13) | hash) + 0x66546b64;
return hash;
}
before cse1:
22: L22:
16: NOTE_INSN_BASIC_BLOCK 4
17: r125:DI=r120:DI+0xd
18: r118:DI=r125:DI|r120:DI
19: r126:DI=r118:DI+0x66540000
20: r120:DI=r126:DI+0x6b64
REG_EQUAL r118:DI+0x66546b64
21: r119:DI=r119:DI-0x1
23: r127:CC=cmp(r119:DI,0)
24: pc={(r127:CC!=0)?L22:pc}
REG_BR_PROB 955630228
The dump in cse1:
16: NOTE_INSN_BASIC_BLOCK 4
17: r125:DI=r120:DI+0xd
18: r118:DI=r125:DI|r120:DI
REG_DEAD r125:DI
REG_DEAD r120:DI
19: r126:DI=r118:DI+0x66540000
REG_DEAD r118:DI
20: r120:DI=r126:DI+0x6b64
REG_DEAD r126:DI
21: r119:DI=r119:DI-0x1
23: r127:CC=cmp(r119:DI,0)
24: pc={(r127:CC!=0)?L22:pc}
REG_DEAD r127:CC
REG_BR_PROB 955630228
; pc falls through to BB 6
The output shows "REQ_EQUAL r118:DI+0x66546b64" is deleted by
df_remove_dead_eq_notes,
but r120:DI is not REG_DEAD here, so is it correct here to check insn use and
find that
r118:DI is dead then do the delete?
Thanks,
Xionghu
