Re: When is the hardware related register is allocated?

[Ian Lance Taylor <iant at google dot com>]

Feng LI <nemokingdom@gmail.com> writes:

> I'm working on a gcc backend, we need to use the information of the
> allocated hardware register to generate the code from builtin
> functions. But at the context in ix86_expand_builtin, where I could
> get the operands which the registers are pseudo registers
> (REGNO(op)>FIRST_PSEUDO_REGISTER).
>
> Do you know where could I get the information of the hardware register
> and generate assemble code from there?

At the point where ix86_expand_builtin is called, the hardware register
is not known.

Typically this kind of thing would be handled via a
define_insn_and_split which represents the operation in some general way
(probably using an UNSPEC) before reload and then splits after reload
based on the registers it winds up seeing.

Ian