Mark Mitchell wrote:
> H.J. Lu wrote:
>
> > http://gcc.gnu.org/ml/gcc-patches/2007-08/msg01865.html
> >
> > which involves reload.
>
> I'm not going to try to wade into reload. Ulrich, Eric, Ian -- would
> one of you please review this patch?
@@ -1821,6 +1835,18 @@ find_reg (struct insn_chain *chain, int
this_cost--;
if (rl->out && REG_P (rl->out) && REGNO (rl->out) == regno)
this_cost--;
+#ifdef SECONDARY_MEMORY_NEEDED
+ /* If a memory location is needed for rl->in and dest_reg
+ is usable, we will favor it. */
+ else if (dest_reg == regno
+ && rl->in
+ && REG_P (rl->in)
+ && REGNO (rl->in) < FIRST_PSEUDO_REGISTER
+ && SECONDARY_MEMORY_NEEDED (REGNO_REG_CLASS (REGNO (rl->in)),
+ rl->class,
+ rl->mode))
+ this_cost = 0;
+#endif
Hmm, this isn't really related to secondary memory. In general,
if we have a simple move with input reload, the destination of
the move should be the preferred reload register. In fact, there
already is code in find_reloads that is supposed to address this
problem:
/* Special case a simple move with an input reload and a
destination of a hard reg, if the hard reg is ok, use it. */
for (i = 0; i < n_reloads; i++)
if (rld[i].when_needed == RELOAD_FOR_INPUT
&& GET_CODE (PATTERN (insn)) == SET
&& REG_P (SET_DEST (PATTERN (insn)))
&& SET_SRC (PATTERN (insn)) == rld[i].in
&& !elimination_target_reg_p (SET_DEST (PATTERN (insn))))
{
This does not trigger in the given test case because the SUBREG
interferes:
Reloads for insn # 6
Reload 0: reload_in (DF) = (reg:DF 5 di)
SSE_REGS, RELOAD_FOR_INPUT (opnum = 1), can't combine
reload_in_reg: (subreg:DF (reg/v:DI 5 di [orig:59 in ] [59]) 0)
(insn:HI 6 3 10 2 xxx.i:4
(set (reg:DF 21 xmm0 [orig:58 <result> ] [58])
(subreg:DF (reg/v:DI 5 di [orig:59 in ] [59]) 0)) 102
{*movdf_integer_rex64} (expr_list:REG_DEAD (reg/v:DI 5 di [orig:59 in ] [59])
(nil)))
Note how reload_in is not equal to the SET_SRC, but reload_in_reg is.
In that case, the same special case should apply.
The following patch fixes the test case for me:
Index: gcc/reload.c
===================================================================
--- gcc/reload.c (revision 129925)
+++ gcc/reload.c (working copy)
@@ -4462,7 +4462,8 @@
if (rld[i].when_needed == RELOAD_FOR_INPUT
&& GET_CODE (PATTERN (insn)) == SET
&& REG_P (SET_DEST (PATTERN (insn)))
- && SET_SRC (PATTERN (insn)) == rld[i].in
+ && (SET_SRC (PATTERN (insn)) == rld[i].in
+ || SET_SRC (PATTERN (insn)) == rld[i].in_reg)
&& !elimination_target_reg_p (SET_DEST (PATTERN (insn))))
{
rtx dest = SET_DEST (PATTERN (insn));
H.J., could you verify that this solves your problem?
Bye,
Ulrich
--
Dr. Ulrich Weigand
GNU Toolchain for Linux on System z and Cell BE
[EMAIL PROTECTED]
