In the general case we simply negate. However with isel we
may load -1 instead of 1 with no extra effort.
Consolidate EQ0 and NE0 logic. Replace the NE0 zero-extension
with inversion+negation of EQ0, which is never worse and may
eliminate one insn. Provide a special case for -EQ0.
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
cba10bb3c8