So my reasoning was that the alternative is likely to be more expensive *on all
cores*, as it is split to two instructions, whereas add/sub "could" be more
expensive for *some* processors.
But yes I can see the argument, by my own logic and James Greenhalgh's, for
removing the '?': it still doesn't really say what we want to say, which is that
the instruction itself is more expensive, rather than anything to do with moving
values into registers if/when reloading. At this point in time we don't have a
framework that allows us to say that...
--Alan
Kugan wrote:
On 13/08/14 00:55, Alan Lawrence wrote:
...patch attached...
Alan Lawrence wrote:
[When I wrote that xor was broken on GPRs and this fixes it, I meant
xor_one_cmpl rather than xor, sorry!]
The pattern for xor_one_cmpl never matched, due to the action of
combine_simplify_rtx; hence, separate this pattern out from that for
ORN/BIC.
ORN/BIC have equivalent SIMD-reg variants, so add those for the
benefit of values in vector registers (e.g. passed as [u]int64x1_t
parameters).
EON does not have a SIMD-reg variant; however, it seems better to
split it (to XOR + NOT) than to move both arguments to GPRs, perform
EON, and move the result back.
+;; (xor (not a) b) is simplify_rtx-ed down to (not (xor a b)).
+;; eon does not operate on SIMD registers so the vector variant must be
split.
+(define_insn_and_split "*xor_one_cmpl<mode>3"
+ [(set (match_operand:GPI 0 "register_operand" "=r,w")
+ (not:GPI (xor:GPI (match_operand:GPI 1 "register_operand" "r,?w")
Hi Alan,
Is there any specific reason for why you are disparaging slightly this
alternative with ‘?’. Your earlier patch removes '!' from subdi3.
Thanks,
Kugan
+ (match_operand:GPI 2 "register_operand"
"r,w"))))]
+ ""
+ "eon\\t%<w>0, %<w>1, %<w>2" ;; For GPR registers (only).
+ "reload_completed && (which_alternative == 1)" ;; For SIMD registers.
+ [(set (match_operand:GPI 0 "register_operand" "=w")
+ (xor:GPI (match_operand:GPI 1 "register_operand" "w")
+ (match_operand:GPI 2 "register_operand" "w")))
+ (set (match_dup 0) (not:GPI (match_dup 0)))]
