target/arm: Implement FCSEL for fp16

These were missed out from the rest of the half-precision work.

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: 20180512003217.9105-10-richard.henderson@linaro.org
[rth: Fix erroneous check vs type]
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target/arm/translate-a64.c

@@ -4903,15 +4903,34 @@ static void disas_fp_csel(DisasContext *s, uint32_t insn)
     unsigned int mos, type, rm, cond, rn, rd;
     TCGv_i64 t_true, t_false, t_zero;
     DisasCompare64 c;
+    TCGMemOp sz;
 
     mos = extract32(insn, 29, 3);
-    type = extract32(insn, 22, 2); /* 0 = single, 1 = double */
+    type = extract32(insn, 22, 2);
     rm = extract32(insn, 16, 5);
     cond = extract32(insn, 12, 4);
     rn = extract32(insn, 5, 5);
     rd = extract32(insn, 0, 5);
 
-    if (mos || type > 1) {
+    if (mos) {
+        unallocated_encoding(s);
+        return;
+    }
+
+    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;
     }
@@ -4920,11 +4939,11 @@ static void disas_fp_csel(DisasContext *s, uint32_t insn)
         return;
     }
 
-    /* Zero extend sreg inputs to 64 bits now.  */
+    /* Zero extend sreg & hreg inputs to 64 bits now.  */
     t_true = tcg_temp_new_i64();
     t_false = tcg_temp_new_i64();
-    read_vec_element(s, t_true, rn, 0, type ? MO_64 : MO_32);
-    read_vec_element(s, t_false, rm, 0, type ? MO_64 : MO_32);
+    read_vec_element(s, t_true, rn, 0, sz);
+    read_vec_element(s, t_false, rm, 0, sz);
 
     a64_test_cc(&c, cond);
     t_zero = tcg_const_i64(0);
@@ -4933,7 +4952,7 @@ static void disas_fp_csel(DisasContext *s, uint32_t insn)
     tcg_temp_free_i64(t_false);
     a64_free_cc(&c);
 
-    /* Note that sregs write back zeros to the high bits,
+    /* Note that sregs & hregs write back zeros to the high bits,
        and we've already done the zero-extension.  */
     write_fp_dreg(s, rd, t_true);
     tcg_temp_free_i64(t_true);