Hi Wilco,
On 18/01/17 06:23, Wilco Dijkstra wrote:
ChangeLog:
2017-01-17 Wilco Dijkstra <wdijk...@arm.com>
* config/arm/arm.md (ashldi3): Remove shift by 1 expansion.
(arm_ashldi3_1bit): Remove pattern.
(ashrdi3): Remove shift by 1 expansion.
(arm_ashrdi3_1bit): Remove pattern.
(lshrdi3): Remove shift by 1 expansion.
(arm_lshrdi3_1bit): Remove pattern.
* config/arm/arm.c (arm_rtx_costs_internal): Slightly increase
cost of ashldi3 by 1.
* config/arm/neon.md (ashldi3_neon): Remove shift by 1 expansion.
(<shift>di3_neon): Likewise.
--
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index
7d82ba358306189535bf7eee08a54e2f84569307..d47f4005446ff3e81968d7888c6573c0360cfdbd
100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -9254,6 +9254,9 @@ arm_rtx_costs_internal (rtx x, enum rtx_code code, enum
rtx_code outer_code,
+ rtx_cost (XEXP (x, 0), mode, code, 0, speed_p));
if (speed_p)
*cost += 2 * extra_cost->alu.shift;
+ /* Slightly disparage left shift by 1 at so we prefer adddi3. */
+ if (code == ASHIFT && XEXP (x, 1) == CONST1_RTX (SImode))
+ *cost += 1;
return true;
}
Your ChangeLog says decrease cost for ashldi3 by 1 but looks like it is
done only for SImode. Am I missing something?
Also, what was the motivation for this patch. Is that to improve the
maintainability of the arm back-end?
Thanks,
Kugan
