question of RTL Generation

[Dale Johannesen]

On Sep 5, 2004, at 7:35 AM, Hsin-Hsien Wu wrote:

> Hello,
>
> Here is a RTL generated by gcc.
> (insn 807 806 812 88 0x401639a0 (set (mem:DI (reg:SI 22 r22 [2]) [2 S8 
> A32])
>         (reg/v:DI 16 r16 [65])) 107 {*target_movdi} (nil)
>     (nil))
>
> I don't want the register allocator to allocate the regs (regs >15) as 
> a
> memory index or base register.
> (insn 807 806 812 88 0x401639a0 (set (mem:DI (reg:SI 22 r22 [2]) [2 S8 
> A32])
>
> ^____ I don't want r22 to be allocated here.
>
> Does any one have the idea ?

This is done with register classes.  See the BASE_REGS class ('b' 
constraint)
in the powerpc port.