From d091ce2d3f5bad6df30c686558807bcffb0c5a96 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Sat, 1 Feb 2025 16:39:35 +0000 Subject: [PATCH] target/arm: Implement FPCR.AH handling for scalar FABS and FABD FPCR.AH == 1 mandates that taking the absolute value of a NaN should not change its sign bit. This means we can no longer use gen_vfp_abs*() everywhere but must instead generate slightly more complex code when FPCR.AH is set. Implement these semantics for scalar FABS and FABD. This change also affects all other instructions whose psuedocode calls FPAbs(); we will extend the change to those instructions in following commits. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson --- target/arm/tcg/translate-a64.c | 69 +++++++++++++++++++++++++++++++++- 1 file changed, 67 insertions(+), 2 deletions(-) diff --git a/target/arm/tcg/translate-a64.c b/target/arm/tcg/translate-a64.c index abd0d916b1..83cfcdc43b 100644 --- a/target/arm/tcg/translate-a64.c +++ b/target/arm/tcg/translate-a64.c @@ -869,6 +869,43 @@ static void gen_vfp_ah_negd(TCGv_i64 d, TCGv_i64 s) s, chs_s); } +/* + * These functions implement + * d = floatN_is_any_nan(s) ? s : floatN_abs(s) + * which for float32 is + * d = (s & ~(1 << 31)) > 0x7f800000UL) ? s : (s & ~(1 << 31)) + * and similarly for the other float sizes. + */ +static void gen_vfp_ah_absh(TCGv_i32 d, TCGv_i32 s) +{ + TCGv_i32 abs_s = tcg_temp_new_i32(); + + gen_vfp_absh(abs_s, s); + tcg_gen_movcond_i32(TCG_COND_GTU, d, + abs_s, tcg_constant_i32(0x7c00), + s, abs_s); +} + +static void gen_vfp_ah_abss(TCGv_i32 d, TCGv_i32 s) +{ + TCGv_i32 abs_s = tcg_temp_new_i32(); + + gen_vfp_abss(abs_s, s); + tcg_gen_movcond_i32(TCG_COND_GTU, d, + abs_s, tcg_constant_i32(0x7f800000UL), + s, abs_s); +} + +static void gen_vfp_ah_absd(TCGv_i64 d, TCGv_i64 s) +{ + TCGv_i64 abs_s = tcg_temp_new_i64(); + + gen_vfp_absd(abs_s, s); + tcg_gen_movcond_i64(TCG_COND_GTU, d, + abs_s, tcg_constant_i64(0x7ff0000000000000ULL), + s, abs_s); +} + static void gen_vfp_maybe_ah_negh(DisasContext *dc, TCGv_i32 d, TCGv_i32 s) { if (dc->fpcr_ah) { @@ -5392,12 +5429,35 @@ static void gen_fabd_d(TCGv_i64 d, TCGv_i64 n, TCGv_i64 m, TCGv_ptr s) gen_vfp_absd(d, d); } +static void gen_fabd_ah_h(TCGv_i32 d, TCGv_i32 n, TCGv_i32 m, TCGv_ptr s) +{ + gen_helper_vfp_subh(d, n, m, s); + gen_vfp_ah_absh(d, d); +} + +static void gen_fabd_ah_s(TCGv_i32 d, TCGv_i32 n, TCGv_i32 m, TCGv_ptr s) +{ + gen_helper_vfp_subs(d, n, m, s); + gen_vfp_ah_abss(d, d); +} + +static void gen_fabd_ah_d(TCGv_i64 d, TCGv_i64 n, TCGv_i64 m, TCGv_ptr s) +{ + gen_helper_vfp_subd(d, n, m, s); + gen_vfp_ah_absd(d, d); +} + static const FPScalar f_scalar_fabd = { gen_fabd_h, gen_fabd_s, gen_fabd_d, }; -TRANS(FABD_s, do_fp3_scalar, a, &f_scalar_fabd, a->rn) +static const FPScalar f_scalar_ah_fabd = { + gen_fabd_ah_h, + gen_fabd_ah_s, + gen_fabd_ah_d, +}; +TRANS(FABD_s, do_fp3_scalar_2fn, a, &f_scalar_fabd, &f_scalar_ah_fabd, a->rn) static const FPScalar f_scalar_frecps = { gen_helper_recpsf_f16, @@ -8643,7 +8703,12 @@ static const FPScalar1Int f_scalar_fabs = { gen_vfp_abss, gen_vfp_absd, }; -TRANS(FABS_s, do_fp1_scalar_int, a, &f_scalar_fabs, true) +static const FPScalar1Int f_scalar_ah_fabs = { + gen_vfp_ah_absh, + gen_vfp_ah_abss, + gen_vfp_ah_absd, +}; +TRANS(FABS_s, do_fp1_scalar_int_2fn, a, &f_scalar_fabs, &f_scalar_ah_fabs) static const FPScalar1Int f_scalar_fneg = { gen_vfp_negh, -- 2.39.5