Re: [PR42861, VTA] bind values to expressions upon MO_VAL_USE

[Steve Ellcey <sje at cup dot hp dot com>]

On Fri, 2010-01-29 at 00:37 +0100, Jakub Jelinek wrote:

> So something like:
> 
> static rtx
> pa_delegitimize_address (rtx orig_x)
> {
>   rtx x = delegitimize_mem_from_attrs (orig_x);
>   if (GET_CODE (x) == LO_SUM
>       && GET_CODE (XEXP (x, 1)) == UNSPEC
>       && XINT (XEXP (x, 1), 1) == UNSPEC_DLTIND14R)
>     return XVECEXP (XEXP (x, 1), 0, 0);
>   return x;
> }
> 
> could do the job.
> 
> 	Jakub

FYI: I am still working on this, I have a small test case that works
before the VTA checkin but fails with the VTA change plus Jakub's
function (when compiled with -O1 or -O2)

The test case is:

f(int n) {
        int i;
        double v[n];
        for(i=0;i<n;i++)
                v[i]=0;
        }

main() {
        f(100);
        exit(0);
}

Before the change v is initialized by writing out %r0 (%r0 always has
zero in it):

        std %r0,0(%r19) ; 84    *pa.md:3933/6   [length = 4]

After the changs v is initialized with this:

        fldd 0(%r0),%fr22       ; 106   *pa.md:3933/8   [length = 4]
        fstd %fr22,0(%r19)      ; 84    *pa.md:3933/9   [length = 4]

Instead of writing out a zero [%r0] it is writing out the contents of
memory location zero [0(%r0)]and that causes a fault.

I am not sure if this is related to why some delegitimize_address
functions have the "if (MEM_P (x)) x = XEXP(x, 0)" code in them or not
but I tried adding that and it didn't seem to help.  The delegitimize
routine is getting called, it is converting:

(lo_sum:DI (reg:DI 156)
    (unspec:DI [
            (symbol_ref/u:DI ("*L$C0000") [flags 0x2])
        ] 2))

into 

(symbol_ref/u:DI ("*L$C0000") [flags 0x2])

Which seems like the right change.  The investigation continues, if I
can't figure out something soon I will submit a bug report and put all
this info in there.

Steve Ellcey
sje@cup.hp.com