tcg: Add preferred_reg argument to tcg_reg_alloc

This new argument will aid register allocation by indicating how
the temporary will be used in future.  If the preference cannot
be satisfied, fall back to the constraints of the current insn.

Short circuit the preference when it cannot be satisfied or if
it does not further constrain the operation.

With an eye toward optimizing function call sequences, optimize
for the preferred_reg set containing a single register.

For the moment, all users pass 0 for preference.

Reviewed-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

0 files changed, 0 insertions, 0 deletions