Well, you're right that it could be. So I presented the wrong justification.
Clearly we would benefit from some better cost infrastructure here, ideally that
is expressive, taken into account at all appropriate stages of the compiler, and
tunable per core. I imagine that steps (patches) towards such infrastructure
would be welcomed by both AArch64 maintainers and more widely.
In the meantime, however, we must work with what we have. I'll still argue that
we should remove the '!' (as per patch), however. As James has said, even if
your add is more expensive in SIMD registers, the '!' still doesn't express
that; and leaving it in affects code-generation on all cores. And it is
inconsistent with other instructions.
--Alan
pins...@gmail.com wrote:
On Aug 12, 2014, at 7:40 AM, Alan Lawrence <alan.lawre...@arm.com> wrote:
(It is no more expensive.)
Yes on some processors it could be.
Thanks,
Andrew
gcc/ChangeLog:
* config/aarch64/aarch64.md (subdi3, adddi3_aarch64): Don't penalize
SIMD reg variant.
diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md index f8eb305140e7b0aed006b33f1724a90939e48316..0a8ca4bcc7941f912c8d42200b33206d4188fa48 100644 --- a/gcc/config/aarch64/aarch64.md +++ b/gcc/config/aarch64/aarch64.md @@ -1188,10 +1188,10 @@ (define_insn "*adddi3_aarch64" [(set -
(match_operand:DI 0 "register_operand" "=rk,rk,rk,!w") + (match_operand:DI 0 "register_operand" "=rk,rk,rk,w") (plus:DI - (match_operand:DI 1 "register_operand" "%rk,rk,rk,!w") - (match_operand:DI 2 "aarch64_plus_operand" "I,r,J,!w")))] +
(match_operand:DI 1 "register_operand" "%rk,rk,rk,w") + (match_operand:DI 2 "aarch64_plus_operand" "I,r,J,w")))] "" "@ add\\t%x0, %x1, %2 @@ -1662,9 +1662,9 @@ ) (define_insn "subdi3" - [(set (match_operand:DI 0 "register_operand"
"=rk,!w") - (minus:DI (match_operand:DI 1 "register_operand" "r,!w") - (match_operand:DI 2 "register_operand" "r,!w")))] + [(set (match_operand:DI 0 "register_operand" "=rk,w") + (minus:DI (match_operand:DI 1 "
register_operand" "r,w") + (match_operand:DI 2 "register_operand" "r,w")))]
"" "@ sub\\t%x0, %x1, %x2
