Re: [sdcc-devel] [ sdcc-Bugs-810093 ] ralloc problem

[Erik P. <epe...@iv...>]

> Unfortunately frexpf.c needs an additional _frexpf_sloc0_1_0 now. My
> reference is a checkout from 03-09-13, where iTemp8 and iTemp11 simply
> share the same registers (in the right order of course). Could you
> please check again, if this optimization could be re-enabled?

This is happening because it also wants to reposition iTemp11's register
allocation from [r6 r7 r0 r1] to [r7 r6 r0 r1] to avoid the lurking
near-miss with r6 in:

; ic:11: iTemp14 {int}[r1 r6] = (xdata-int)iTemp11 [r6 r7 r0 r1]
;     genCast
        mov     ar1,r6
        mov     ar6,r7

In this particular case we were lucky and nothing bad really happened.
However in bug #762602, the compiler was also doing a cast using the
same positioning algorithm (but a different register allocation) and
generated:

;     genCast
	mov ar3, r2
	mov ar4, r3 <---The original r3 is already lost

There is certainly room for improvement in the register allocation
process; I was just focused on fixing the parts that lead to incorrect
code. I'll see if I can find a good way (that is, not involving a lot of
exception cases) to have both correct and more optimal code.

  Erik