https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108038
--- Comment #1 from Raphael M Zinsly <rzinsly at ventanamicro dot com> ---
(In reply to Jeffrey A. Law from comment #0)
> testGT:
> sgt a0,a0,a1 # 25 [c=4 l=4] *sgt_didi
> xori a0,a0,1 # 27 [c=4 l=4] xordi3/1
> addi a0,a0,2 # 16 [c=4 l=4] adddi3/1
> ret # 35 [c=0 l=4] simple_return
>
>
> But ISTM we could generate this instead:
>
> testGT:
> sgt a0,a1,a0 # 24 [c=4 l=4] *riscv.md:2535
> addi a0,a0,2 # 16 [c=4 l=4] adddi3/1
> ret # 32 [c=0 l=4] simple_return
Unless I'm missing something this seems wrong: 'sgt a0,a0,a1' with 'xori
a0,a0,1' would be equivalent to 'sge a0,a1,a0' or to 'sle a0,a0,a1' and not to
'sgt a0,a1,a0'.
For x == y the result would be 2 with your asm.
> We can invert the condition and swap the operands with something like this:
>
> (define_insn ""
> [(set (match_operand:GPR 0 "register_operand" "=r")
> (any_le:GPR (match_operand:X 1 "register_operand" " r")
> (match_operand:X 2 "register_operand" "r")))]
> ""
> "sgt<u>\t%0,%2,%1"
> [(set_attr "type" "slt")
> (set_attr "mode" "<X:MODE>")])
This works as you intended. However, I think the right patter should be:
(define_insn "*sge<u>_<X:mode><GPR:mode>_inv"
[(set (match_operand:GPR 0 "register_operand" "=r")
(any_le:GPR (match_operand:X 1 "register_operand" " r")
(match_operand:X 2 "register_operand" "r")))]
""
"sge<u>\t%0,%2,%1"
[(set_attr "type" "slt")
(set_attr "mode" "<X:MODE>")])
It produces the output:
testGT:
sge a0,a1,a0 # 24 [c=4 l=4] *sge_didi_inv
addi a0,a0,2 # 16 [c=4 l=4] adddi3/1
ret # 32 [c=0 l=4] simple_return
