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combine.c (unmentioned_reg_p): New function to check whether an expression is a "specialization" of another, i.e. 

* combine.c (unmentioned_reg_p): New function to check whether an
	expression is a "specialization" of another, i.e. that there are
	no registers or memory references mentioned in the first that don't
	appear in the second.
	(unmentioned_reg_p_1): New helper subroutine of unmentioned_reg_p.
	(combine_instructions): Also try combining instructions using the
	REG_EQUAL note from a preceding log-linked instruction.

From-SVN: r79398
This commit is contained in:
Roger Sayle 2004-03-12 17:38:30 +00:00 committed by Roger Sayle
parent 8937b6a209
commit 67962db535
2 changed files with 64 additions and 0 deletions
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10
gcc/ChangeLog
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@ -1,3 +1,13 @@
2004-03-12 Roger Sayle <roger@eyesopen.com>
* combine.c (unmentioned_reg_p): New function to check whether an
expression is a "specialization" of another, i.e. that there are
no registers or memory references mentioned in the first that don't
appear in the second.
(unmentioned_reg_p_1): New helper subroutine of unmentioned_reg_p.
(combine_instructions): Also try combining instructions using the
REG_EQUAL note from a preceding log-linked instruction.
2004-03-12 Roger Sayle <roger@eyesopen.com>
* config/i386/i386.c (ix86_split_ashrdi): Optimize shift by 63.

54
gcc/combine.c
View File

@ -407,6 +407,8 @@ static int insn_cuid (rtx);
static void record_promoted_value (rtx, rtx);
static rtx reversed_comparison (rtx, enum machine_mode, rtx, rtx);
static enum rtx_code combine_reversed_comparison_code (rtx);
static int unmentioned_reg_p_1 (rtx *, void *);
static bool unmentioned_reg_p (rtx, rtx);
/* Substitute NEWVAL, an rtx expression, into INTO, a place in some
insn. The substitution can be undone by undo_all. If INTO is already
@ -720,6 +722,31 @@ combine_instructions (rtx f, unsigned int nregs)
&new_direct_jump_p)) != 0)
goto retry;
/* Try this insn with each REG_EQUAL note it links back to. */
for (links = LOG_LINKS (insn); links; links = XEXP (links, 1))
{
rtx set, note;
rtx temp = XEXP (links, 0);
if ((set = single_set (temp)) != 0
&& (note = find_reg_equal_equiv_note (temp)) != 0
&& GET_CODE (XEXP (note, 0)) != EXPR_LIST
/* Avoid using a register that may already been marked
dead by an earlier instruction. */
&& ! unmentioned_reg_p (XEXP (note, 0), SET_SRC (set)))
{
/* Temporarily replace the set's source with the
contents of the REG_EQUAL note. The insn will
be deleted or recognized by try_combine. */
rtx orig = SET_SRC (set);
SET_SRC (set) = XEXP (note, 0);
next = try_combine (insn, temp, NULL_RTX,
&new_direct_jump_p);
if (next)
goto retry;
SET_SRC (set) = orig;
}
}
if (GET_CODE (insn) != NOTE)
record_dead_and_set_regs (insn);
@ -12979,6 +13006,33 @@ distribute_links (rtx links)
}
}
/* Subroutine of unmentioned_reg_p and callback from for_each_rtx.
Check whether the expression pointer to by LOC is a register or
memory, and if so return 1 if it isn't mentioned in the rtx EXPR.
Otherwise return zero. */
static int
unmentioned_reg_p_1 (rtx *loc, void *expr)
{
rtx x = *loc;
if (x != NULL_RTX
&& (GET_CODE (x) == REG || GET_CODE (x) == MEM)
&& ! reg_mentioned_p (x, (rtx) expr))
return 1;
return 0;
}
/* Check for any register or memory mentioned in EQUIV that is not
mentioned in EXPR. This is used to restrict EQUIV to "specializations"
of EXPR where some registers may have been replaced by constants. */
static bool
unmentioned_reg_p (rtx equiv, rtx expr)
{
return for_each_rtx (&equiv, unmentioned_reg_p_1, expr);
}
/* Compute INSN_CUID for INSN, which is an insn made by combine. */
static int