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re PR rtl-optimization/42699 (ZERO_EXTRACT on lhs never optimized out)

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PR rtl-optimization/42699
	* cse.c (cse_insn): Optimize lhs ZERO_EXTRACT if only CONST_INTs are
	involved.

From-SVN: r155844
This commit is contained in:
Jakub Jelinek 2010-01-12 21:25:10 +01:00 committed by Jakub Jelinek
parent 932f6f4a2c
commit b4ab701fcc
2 changed files with 85 additions and 0 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2010-01-12 Jakub Jelinek <jakub@redhat.com>
PR rtl-optimization/42699
* cse.c (cse_insn): Optimize lhs ZERO_EXTRACT if only CONST_INTs are
involved.
2010-01-12 Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE>
* config/mips/iris6.h (SUBTARGET_DONT_WARN_UNUSED_SPEC,

79
gcc/cse.c
View File

@ -4436,6 +4436,7 @@ cse_insn (rtx insn)
for (i = 0; i < n_sets; i++)
{
bool repeat = false;
rtx src, dest;
rtx src_folded;
struct table_elt *elt = 0, *p;
@ -5029,6 +5030,77 @@ cse_insn (rtx insn)
break;
}
/* Try to optimize
(set (reg:M N) (const_int A))
(set (reg:M2 O) (const_int B))
(set (zero_extract:M2 (reg:M N) (const_int C) (const_int D))
(reg:M2 O)). */
if (GET_CODE (SET_DEST (sets[i].rtl)) == ZERO_EXTRACT
&& CONST_INT_P (trial)
&& CONST_INT_P (XEXP (SET_DEST (sets[i].rtl), 1))
&& CONST_INT_P (XEXP (SET_DEST (sets[i].rtl), 2))
&& REG_P (XEXP (SET_DEST (sets[i].rtl), 0))
&& (GET_MODE_BITSIZE (GET_MODE (SET_DEST (sets[i].rtl)))
>= INTVAL (XEXP (SET_DEST (sets[i].rtl), 1)))
&& ((unsigned) INTVAL (XEXP (SET_DEST (sets[i].rtl), 1))
+ (unsigned) INTVAL (XEXP (SET_DEST (sets[i].rtl), 2))
<= HOST_BITS_PER_WIDE_INT))
{
rtx dest_reg = XEXP (SET_DEST (sets[i].rtl), 0);
rtx width = XEXP (SET_DEST (sets[i].rtl), 1);
rtx pos = XEXP (SET_DEST (sets[i].rtl), 2);
unsigned int dest_hash = HASH (dest_reg, GET_MODE (dest_reg));
struct table_elt *dest_elt
= lookup (dest_reg, dest_hash, GET_MODE (dest_reg));
rtx dest_cst = NULL;
if (dest_elt)
for (p = dest_elt->first_same_value; p; p = p->next_same_value)
if (p->is_const && CONST_INT_P (p->exp))
{
dest_cst = p->exp;
break;
}
if (dest_cst)
{
HOST_WIDE_INT val = INTVAL (dest_cst);
HOST_WIDE_INT mask;
unsigned int shift;
if (BITS_BIG_ENDIAN)
shift = GET_MODE_BITSIZE (GET_MODE (dest_reg))
- INTVAL (pos) - INTVAL (width);
else
shift = INTVAL (pos);
if (INTVAL (width) == HOST_BITS_PER_WIDE_INT)
mask = ~(HOST_WIDE_INT) 0;
else
mask = ((HOST_WIDE_INT) 1 << INTVAL (width)) - 1;
val &= ~(mask << shift);
val |= (INTVAL (trial) & mask) << shift;
val = trunc_int_for_mode (val, GET_MODE (dest_reg));
validate_unshare_change (insn, &SET_DEST (sets[i].rtl),
dest_reg, 1);
validate_unshare_change (insn, &SET_SRC (sets[i].rtl),
GEN_INT (val), 1);
if (apply_change_group ())
{
rtx note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
if (note)
{
remove_note (insn, note);
df_notes_rescan (insn);
}
src_eqv = NULL_RTX;
src_eqv_elt = NULL;
src_eqv_volatile = 0;
src_eqv_in_memory = 0;
src_eqv_hash = 0;
repeat = true;
break;
}
}
}
/* We don't normally have an insn matching (set (pc) (pc)), so
check for this separately here. We will delete such an
insn below.
@ -5104,6 +5176,13 @@ cse_insn (rtx insn)
}
}
/* If we changed the insn too much, handle this set from scratch. */
if (repeat)
{
i--;
continue;
}
src = SET_SRC (sets[i].rtl);
/* In general, it is good to have a SET with SET_SRC == SET_DEST.