Re: [Qemu-devel] [PATCH v2 15/32] arm/translate-a64: add FP16 FMULX/MLS/FMLA to simd_indexed

[Richard Henderson <richard.henderson@linaro.org>]

On 02/08/2018 09:31 AM, Alex Bennée wrote:
> The helpers use the new re-factored muladd support in SoftFloat for the 
> float16 work.
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org> --- 
> target/arm/translate-a64.c | 69 
> ++++++++++++++++++++++++++++++++++++---------- 1 file changed, 54 
> insertions(+), 15 deletions(-)
> 
> diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c index 
> 3a2be1e016..83a1fa3116 100644 --- a/target/arm/translate-a64.c +++ 
> b/target/arm/translate-a64.c @@ -10804,7 +10804,7 @@ static void 
> disas_simd_indexed(DisasContext *s, uint32_t insn) } /* fall through */
> case 0x9: /* FMUL, FMULX */ -        if (!extract32(size, 1, 1)) { +
> if (size == 1 || (size < 2 && !arm_dc_feature(s, ARM_FEATURE_V8_FP16))) { 
> unallocated_encoding(s); return; } @@ -10816,18 +10816,30 @@ static void 
> disas_simd_indexed(DisasContext *s, uint32_t insn) }
> 
> if (is_fp) { -        /* low bit of size indicates single/double */ - size =
> extract32(size, 0, 1) ? 3 : 2; -        if (size == 2) { +        /* convert
> insn encoded size to TCGMemOp size */ +        switch (size) { + case 0: /*
> half-precision */ +            size = MO_16; +            index = h << 2 | l
> << 1 | m; +            break;

FWIW, the size check for the integer insns is done in this block (in the !is_fp
side of course).  I think it makes sense to do the size check for FP insns down
here too.  So, e.g.

    if (is_fp) {
        switch (size) {
        case 2: /* single precision */
            ...
        case 3: /* double precision */
            ...
        case 0: /* half precision */
            size = MO_16;
            index = ...
            is_fp16 = true;
            if (arm_dc_feature(s, ARM_FEATURE_V8_FP16)) {
                break;
            }
            /* fallthru */
        default: /* unallocated */
            unallocated_encoding(s);
            return;
        }
    }

Just below, you have not updated the call to get_fpstatus_ptr.
For the record, for fcmla I needed to introduce an "is_fp16" bool here.
(Since of course a complex fp16 is 32-bits wide.)


r~