target/arm: Implement fp16 for Neon VRSQRTS

Convert the Neon VRSQRTS insn to using a gvec helper,
and use this to implement the fp16 case.

As with VRECPS, we adjust the phrasing of the new implementation
slightly so that the fp32 version parallels the fp16 one.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200828183354.27913-35-peter.maydell@linaro.org

diff --git a/target/arm/helper.h b/target/arm/helper.h
index 114039c4c339917d908e89c4a2aa8413954358f7..5a716498913d1b70f8df36d09af61c4806bf1189 100644 (file)
--- a/target/arm/helper.h
+++ b/target/arm/helper.h
@@ -225,7 +225,6 @@ DEF_HELPER_4(vfp_muladdd, f64, f64, f64, f64, ptr)
 DEF_HELPER_4(vfp_muladds, f32, f32, f32, f32, ptr)
 DEF_HELPER_4(vfp_muladdh, f16, f16, f16, f16, ptr)
 
-DEF_HELPER_3(rsqrts_f32, f32, env, f32, f32)
 DEF_HELPER_FLAGS_2(recpe_f16, TCG_CALL_NO_RWG, f16, f16, ptr)
 DEF_HELPER_FLAGS_2(recpe_f32, TCG_CALL_NO_RWG, f32, f32, ptr)
 DEF_HELPER_FLAGS_2(recpe_f64, TCG_CALL_NO_RWG, f64, f64, ptr)
@@ -676,6 +675,9 @@ DEF_HELPER_FLAGS_5(gvec_fminnum_s, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, ptr, i3
 DEF_HELPER_FLAGS_5(gvec_recps_nf_h, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, ptr, i32)
 DEF_HELPER_FLAGS_5(gvec_recps_nf_s, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, ptr, i32)
 
+DEF_HELPER_FLAGS_5(gvec_rsqrts_nf_h, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, ptr, i32)
+DEF_HELPER_FLAGS_5(gvec_rsqrts_nf_s, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, ptr, i32)
+
 DEF_HELPER_FLAGS_5(gvec_fmla_h, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, ptr, i32)
 DEF_HELPER_FLAGS_5(gvec_fmla_s, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, ptr, i32)
 

diff --git a/target/arm/translate-neon.c.inc b/target/arm/translate-neon.c.inc
index 63e7be8e01db1194568cf0d73e4543a383561b56..4c6d63be3d344c3fa40b53db3d9bfc34a663cd75 100644 (file)
--- a/target/arm/translate-neon.c.inc
+++ b/target/arm/translate-neon.c.inc
@@ -1075,6 +1075,7 @@ DO_3S_FP_GVEC(VMLS, gen_helper_gvec_fmls_s, gen_helper_gvec_fmls_h)
 DO_3S_FP_GVEC(VFMA, gen_helper_gvec_vfma_s, gen_helper_gvec_vfma_h)
 DO_3S_FP_GVEC(VFMS, gen_helper_gvec_vfms_s, gen_helper_gvec_vfms_h)
 DO_3S_FP_GVEC(VRECPS, gen_helper_gvec_recps_nf_s, gen_helper_gvec_recps_nf_h)
+DO_3S_FP_GVEC(VRSQRTS, gen_helper_gvec_rsqrts_nf_s, gen_helper_gvec_rsqrts_nf_h)
 
 WRAP_FP_GVEC(gen_VMAXNM_fp32_3s, FPST_STD, gen_helper_gvec_fmaxnum_s)
 WRAP_FP_GVEC(gen_VMAXNM_fp16_3s, FPST_STD_F16, gen_helper_gvec_fmaxnum_h)
@@ -1111,26 +1112,6 @@ static bool trans_VMINNM_fp_3s(DisasContext *s, arg_3same *a)
     return do_3same(s, a, gen_VMINNM_fp32_3s);
 }
 
-WRAP_ENV_FN(gen_VRSQRTS_tramp, gen_helper_rsqrts_f32)
-
-static void gen_VRSQRTS_fp_3s(unsigned vece, uint32_t rd_ofs,
-                              uint32_t rn_ofs, uint32_t rm_ofs,
-                              uint32_t oprsz, uint32_t maxsz)
-{
-    static const GVecGen3 ops = { .fni4 = gen_VRSQRTS_tramp };
-    tcg_gen_gvec_3(rd_ofs, rn_ofs, rm_ofs, oprsz, maxsz, &ops);
-}
-
-static bool trans_VRSQRTS_fp_3s(DisasContext *s, arg_3same *a)
-{
-    if (a->size != 0) {
-        /* TODO fp16 support */
-        return false;
-    }
-
-    return do_3same(s, a, gen_VRSQRTS_fp_3s);
-}
-
 static bool do_3same_fp_pair(DisasContext *s, arg_3same *a, VFPGen3OpSPFn *fn)
 {
     /* FP operations handled pairwise 32 bits at a time */

diff --git a/target/arm/vec_helper.c b/target/arm/vec_helper.c
index 0111a23024467f2c25e146b2dd5b6ebe4f0076e6..e5bb5e395cbfee482d679b8238507edd311b3e43 100644 (file)
--- a/target/arm/vec_helper.c
+++ b/target/arm/vec_helper.c
@@ -825,6 +825,33 @@ static float32 float32_recps_nf(float32 op1, float32 op2, float_status *stat)
     return float32_sub(float32_two, float32_mul(op1, op2, stat), stat);
 }
 
+/* Reciprocal square-root step. AArch32 non-fused semantics. */
+static float16 float16_rsqrts_nf(float16 op1, float16 op2, float_status *stat)
+{
+    op1 = float16_squash_input_denormal(op1, stat);
+    op2 = float16_squash_input_denormal(op2, stat);
+
+    if ((float16_is_infinity(op1) && float16_is_zero(op2)) ||
+        (float16_is_infinity(op2) && float16_is_zero(op1))) {
+        return float16_one_point_five;
+    }
+    op1 = float16_sub(float16_three, float16_mul(op1, op2, stat), stat);
+    return float16_div(op1, float16_two, stat);
+}
+
+static float32 float32_rsqrts_nf(float32 op1, float32 op2, float_status *stat)
+{
+    op1 = float32_squash_input_denormal(op1, stat);
+    op2 = float32_squash_input_denormal(op2, stat);
+
+    if ((float32_is_infinity(op1) && float32_is_zero(op2)) ||
+        (float32_is_infinity(op2) && float32_is_zero(op1))) {
+        return float32_one_point_five;
+    }
+    op1 = float32_sub(float32_three, float32_mul(op1, op2, stat), stat);
+    return float32_div(op1, float32_two, stat);
+}
+
 #define DO_3OP(NAME, FUNC, TYPE) \
 void HELPER(NAME)(void *vd, void *vn, void *vm, void *stat, uint32_t desc) \
 {                                                                          \
@@ -885,6 +912,9 @@ DO_3OP(gvec_fminnum_s, float32_minnum, float32)
 DO_3OP(gvec_recps_nf_h, float16_recps_nf, float16)
 DO_3OP(gvec_recps_nf_s, float32_recps_nf, float32)
 
+DO_3OP(gvec_rsqrts_nf_h, float16_rsqrts_nf, float16)
+DO_3OP(gvec_rsqrts_nf_s, float32_rsqrts_nf, float32)
+
 #ifdef TARGET_AARCH64
 
 DO_3OP(gvec_recps_h, helper_recpsf_f16, float16)

diff --git a/target/arm/vfp_helper.c b/target/arm/vfp_helper.c
index 1f452409d4d3dc839c654f0dd53ac79679ea94b0..8a3dd1768196c9502c6c16867642b6cd07c54479 100644 (file)
--- a/target/arm/vfp_helper.c
+++ b/target/arm/vfp_helper.c
@@ -529,21 +529,6 @@ uint32_t HELPER(vfp_fcvt_f64_to_f16)(float64 a, void *fpstp, uint32_t ahp_mode)
     return r;
 }
 
-float32 HELPER(rsqrts_f32)(CPUARMState *env, float32 a, float32 b)
-{
-    float_status *s = &env->vfp.standard_fp_status;
-    float32 product;
-    if ((float32_is_infinity(a) && float32_is_zero_or_denormal(b)) ||
-        (float32_is_infinity(b) && float32_is_zero_or_denormal(a))) {
-        if (!(float32_is_zero(a) || float32_is_zero(b))) {
-            float_raise(float_flag_input_denormal, s);
-        }
-        return float32_one_point_five;
-    }
-    product = float32_mul(a, b, s);
-    return float32_div(float32_sub(float32_three, product, s), float32_two, s);
-}
-
 /* NEON helpers.  */
 
 /* Constants 256 and 512 are used in some helpers; we avoid relying on