target/arm: Convert V[US]DOT (scalar) to decodetree

Convert the V[US]DOT (scalar) insns in the 2reg-scalar-ext group
to decodetree.

Backports commit 35f5d4d1747558c6af2d914bcd848dcc30c3b531 from qemu

qemu/target/arm/neon-shared.decode

@@ -54,3 +54,6 @@ VCMLA_scalar   1111 1110 0 . rot:2 .... .... 1000 . q:1 index:1 0 vm:4 \
                vn=%vn_dp vd=%vd_dp size=0
 VCMLA_scalar   1111 1110 1 . rot:2 .... .... 1000 . q:1 . 0 .... \
                vm=%vm_dp vn=%vn_dp vd=%vd_dp size=1 index=0
+
+VDOT_scalar    1111 1110 0 . 10 .... .... 1101 . q:1 index:1 u:1 rm:4 \
+               vm=%vm_dp vn=%vn_dp vd=%vd_dp

qemu/target/arm/translate-neon.inc.c

@@ -212,3 +212,39 @@ static bool trans_VCMLA_scalar(DisasContext *s, arg_VCMLA_scalar *a)
     tcg_temp_free_ptr(tcg_ctx, fpst);
     return true;
 }
+
+static bool trans_VDOT_scalar(DisasContext *s, arg_VDOT_scalar *a)
+{
+    gen_helper_gvec_3 *fn_gvec;
+    int opr_sz;
+    TCGv_ptr fpst;
+    TCGContext *tcg_ctx = s->uc->tcg_ctx;
+
+    if (!dc_isar_feature(aa32_dp, s)) {
+        return false;
+    }
+
+    /* UNDEF accesses to D16-D31 if they don't exist. */
+    if (!dc_isar_feature(aa32_simd_r32, s) &&
+        ((a->vd | a->vn) & 0x10)) {
+        return false;
+    }
+
+    if ((a->vd | a->vn) & a->q) {
+        return false;
+    }
+
+    if (!vfp_access_check(s)) {
+        return true;
+    }
+
+    fn_gvec = a->u ? gen_helper_gvec_udot_idx_b : gen_helper_gvec_sdot_idx_b;
+    opr_sz = (1 + a->q) * 8;
+    fpst = get_fpstatus_ptr(s, 1);
+    tcg_gen_gvec_3_ool(tcg_ctx, vfp_reg_offset(1, a->vd),
+                       vfp_reg_offset(1, a->vn),
+                       vfp_reg_offset(1, a->rm),
+                       opr_sz, opr_sz, a->index, fn_gvec);
+    tcg_temp_free_ptr(tcg_ctx, fpst);
+    return true;
+}

qemu/target/arm/translate.c

@@ -7182,18 +7182,7 @@ static int disas_neon_insn_2reg_scalar_ext(DisasContext *s, uint32_t insn)
     bool is_long = false, q = extract32(insn, 6, 1);
     bool ptr_is_env = false;
 
-    if ((insn & 0xffb00f00) == 0xfe200d00) {
+    if ((insn & 0xffa00f10) == 0xfe000810) {
-        /* V[US]DOT -- 1111 1110 0.10 .... .... 1101 .Q.U .... */
-        int u = extract32(insn, 4, 1);
-
-        if (!dc_isar_feature(aa32_dp, s)) {
-            return 1;
-        }
-        fn_gvec = u ? gen_helper_gvec_udot_idx_b : gen_helper_gvec_sdot_idx_b;
-        /* rm is just Vm, and index is M.  */
-        data = extract32(insn, 5, 1); /* index */
-        rm = extract32(insn, 0, 4);
-    } else if ((insn & 0xffa00f10) == 0xfe000810) {
         /* VFM[AS]L -- 1111 1110 0.0S .... .... 1000 .Q.1 .... */
         int is_s = extract32(insn, 20, 1);
         int vm20 = extract32(insn, 0, 3);