Re: [PATCH 3/3] tests/tcg/s390x: test signed vfmin/vfmax

[Ilya Leoshkevich <iii@linux.ibm.com>]

On Tue, 2022-07-12 at 10:19 +0530, Richard Henderson wrote:
> On 7/12/22 07:27, Ilya Leoshkevich wrote:
> > +/*
> > + * vfmin/vfmax code generation.
> > + */
> > +extern const char vfminmax_template[];
> > +extern const int vfminmax_template_size;
> > +extern const int vfminmax_offset;
> > +asm(".globl vfminmax_template\n"
> > +    "vfminmax_template:\n"
> > +    "vl %v25,0(%r3)\n"
> > +    "vl %v26,0(%r4)\n"
> > +    "0: vfmax %v24,%v25,%v26,2,0,0\n"
> > +    "vst %v24,0(%r2)\n"
> > +    "br %r14\n"
> > +    "1: .align 4\n"
> > +    ".globl vfminmax_template_size\n"
> > +    "vfminmax_template_size: .long 1b - vfminmax_template\n"
> > +    ".globl vfminmax_offset\n"
> > +    "vfminmax_offset: .long 0b - vfminmax_template\n");
> ...
> > +
> > +#define VFMIN 0xEE
> > +#define VFMAX 0xEF
> > +
> > +static void vfminmax(unsigned char *buf, unsigned int op,
> > +                     unsigned int m4, unsigned int m5, unsigned
> > int m6,
> > +                     void *v1, const void *v2, const void *v3)
> > +{
> > +    memcpy(buf, vfminmax_template, vfminmax_template_size);
> > +    buf[vfminmax_offset + 3] = (m6 << 4) | m5;
> > +    buf[vfminmax_offset + 4] &= 0x0F;
> > +    buf[vfminmax_offset + 4] |= (m4 << 4);
> > +    buf[vfminmax_offset + 5] = op;
> > +    ((void (*)(void *, const void *, const void *))buf)(v1, v2,
> > v3);
> > +}
> 
> This works, of course.  It could be simpler using EXECUTE, to store
> just the one 
> instruction and not worry about an executable mapped page, but I
> guess it doesn't matter.
> 
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> 
> 
> r~

Thanks!

I thought about this too, but EX/EXRL operate only on the second byte,
and I need to modify bytes 3-5 here.