target/arm: Implement FMOV (immediate) for fp16

All the hard work is already done by vfp_expand_imm, we just need to
make sure we pick up the correct size.

Cc: qemu-stable@nongnu.org
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NAlex Bennée <alex.bennee@linaro.org>
Tested-by: NAlex Bennée <alex.bennee@linaro.org>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20180512003217.9105-11-richard.henderson@linaro.org
[rth: Merge unallocated_encoding check with TCGMemOp conversion.]
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target/arm/translate-a64.c

@@ -5674,11 +5674,25 @@ static void disas_fp_imm(DisasContext *s, uint32_t insn)
 {
     int rd = extract32(insn, 0, 5);
     int imm8 = extract32(insn, 13, 8);
-    int is_double = extract32(insn, 22, 2);
+    int type = extract32(insn, 22, 2);
     uint64_t imm;
     TCGv_i64 tcg_res;
+    TCGMemOp sz;
 
-    if (is_double > 1) {
+    switch (type) {
+    case 0:
+        sz = MO_32;
+        break;
+    case 1:
+        sz = MO_64;
+        break;
+    case 3:
+        sz = MO_16;
+        if (arm_dc_feature(s, ARM_FEATURE_V8_FP16)) {
+            break;
+        }
+        /* fallthru */
+    default:
         unallocated_encoding(s);
         return;
     }
@@ -5687,7 +5701,7 @@ static void disas_fp_imm(DisasContext *s, uint32_t insn)
         return;
     }
 
-    imm = vfp_expand_imm(MO_32 + is_double, imm8);
+    imm = vfp_expand_imm(sz, imm8);
 
     tcg_res = tcg_const_i64(imm);
     write_fp_dreg(s, rd, tcg_res);