Postreload may transform (set (REGX) (CONST_INT A)) ... (set (REGX)
(CONST_INT B)) to (set (REGX) (CONST_INT A)) ... (set (STRICT_LOW_PART
(REGX)) (CONST_INT B)), but it should do that only if the latter is
cheaper. On m68k, a full word load of a small constant with moveq is
cheaper than doing a byte load with move.b.
Tested on m68k-suse-linux and x86_64-suse-linux. In both cases the size
of cc1* becomes smaller with this change.
Andreas.
PR rtl-optimization/54555
* postreload.c (move2add_use_add2_insn): Only substitute
STRICT_LOW_PART if it is cheaper.
---
gcc/postreload.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/gcc/postreload.c b/gcc/postreload.c
index 9d71649..89f0c84 100644
--- a/gcc/postreload.c
+++ b/gcc/postreload.c
@@ -1805,10 +1805,14 @@ move2add_use_add2_insn (rtx reg, rtx sym, rtx off, rtx
insn)
gen_rtx_STRICT_LOW_PART (VOIDmode,
narrow_reg),
narrow_src);
- changed = validate_change (insn, &PATTERN (insn),
- new_set, 0);
- if (changed)
- break;
+ get_full_set_rtx_cost (new_set, &newcst);
+ if (costs_lt_p (&newcst, &oldcst, speed))
+ {
+ changed = validate_change (insn, &PATTERN (insn),
+ new_set, 0);
+ if (changed)
+ break;
+ }
}
}
}
--
2.0.0
--
Andreas Schwab, SUSE Labs, sch...@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."
