RE: [RFC PATCH v3 07/34] Hexagon (target/hexagon) scalar core helpers

[Taylor Simpson]

> -----Original Message-----
> From: Richard Henderson <richard.henderson@linaro.org>
> Sent: Wednesday, August 26, 2020 8:17 AM
> To: Taylor Simpson <tsimpson@quicinc.com>; qemu-devel@nongnu.org
> Cc: philmd@redhat.com; laurent@vivier.eu; riku.voipio@iki.fi;
> aleksandar.m.mail@gmail.com; ale@rev.ng
> Subject: Re: [RFC PATCH v3 07/34] Hexagon (target/hexagon) scalar core
> helpers
>
> > +DEF_HELPER_3(merge_inflight_store8u, s64, env, s32, s64)
>
> Please use DEF_HELPER_FLAGS_N when possible.

OK

> > +static inline void log_pred_write(CPUHexagonState *env, int pnum,
> > +                                  target_ulong val)
>
> You might be better off letting the compiler decide about inlining.

Isn't "inline" just a hint to the compiler?

> > +    union {
> > +        uint8_t bytes[8];
> > +        uint32_t data32;
> > +        uint64_t data64;
> > +    } retdata, storedata;
>
> Red flag here.  This is assuming that the host and the target are both
> little-endian.

OK

> > +    int bigmask = ((-load_width) & (-store_width));
> > +    if ((load_addr & bigmask) != (store_addr & bigmask)) {
>
> Huh?  This doesn't detect overlap.  Counter example:
>
>   load_addr = 0, load_width = 4,
>   store_addr = 1, store_width = 1.
>
>   bigmask = -4 & -1 -> -4.
>
>   (0 & -4) != (1 & -4) -> 0 != 1

OK

> > +    while ((i < load_width) && (j < store_width)) {
> > +        retdata.bytes[i] = storedata.bytes[j];
> > +        i++;
> > +        j++;
> > +    }
> > +    return retdata.data64;
>
> This most definitely requires host-endian adjustment.

OK

> > +/* Helpful for printing intermediate values within instructions */
> > +void HELPER(debug_value)(CPUHexagonState *env, int32_t value)
> > +{
> > +    HEX_DEBUG_LOG("value = 0x%x\n", value);
> > +}
> > +
> > +void HELPER(debug_value_i64)(CPUHexagonState *env, int64_t value)
> > +{
> > +    HEX_DEBUG_LOG("value_i64 = 0x%lx\n", value);
> > +}
>
> I think we need to lose all of this.
> There are other ways to debug TCG.

OK