Re: Indirect memory addresses vs. lra

[Vladimir Makarov <vmakarov at redhat dot com>]

On 2019-08-10 2:05 a.m., John Darrington wrote:
> On Fri, Aug 09, 2019 at 01:34:36PM -0400, Vladimir Makarov wrote:
>       
>       If you provide LRA dump for such test (it is better to use
>       -fira-verbose=15 to output full RA info into stderr), I probably could
>       say more.
>
> I've attached such a dump (generated from gcc/testsuite/gcc.c-torture/compile/pr53410-2.c).

Unfortunately, this info is not enough for me to say what is the 
problem.  I only found suspicious that LRA is trying to assign a few 
registers to a pseudo register and fails even though these registers are 
not assigned to anything.  Probably HARD_REGNO_MODE_OK prevents this.  
So it would be interesting to know how many registers of Pmode are 
actually available.

In any case I'll try to look at this problem more on this week using 
your built gcc on gcc135.

>       
>       The less regs the architecture has, thoke easier to run into such error
>       message if something described wrong in the back-end.?? I see your
>       architecture is 16-bit micro-controller with only 8 regs, some of them is
>       specialized.?? So your architecture is really register constrained.
>
> That's not quite correct.  It is a 24-bit micro-controller (the address
> space is 24 bits wide).  There are 2 address registers (plus stack
> pointer and program counter) and there are 8 general purpose data
> registers (of differing sizes).
>