target-arm: A64: Add support for floating point compare

Add decoding support for C3.6.22 Floating-point compare.

Signed-off-by: Claudio Fontana <claudio.fontana@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>

target-arm/helper-a64.c

@@ -77,3 +77,48 @@ uint64_t HELPER(rbit64)(uint64_t x)
 
     return x;
 }
+
+/* Convert a softfloat float_relation_ (as returned by
+ * the float*_compare functions) to the correct ARM
+ * NZCV flag state.
+ */
+static inline uint32_t float_rel_to_flags(int res)
+{
+    uint64_t flags;
+    switch (res) {
+    case float_relation_equal:
+        flags = PSTATE_Z | PSTATE_C;
+        break;
+    case float_relation_less:
+        flags = PSTATE_N;
+        break;
+    case float_relation_greater:
+        flags = PSTATE_C;
+        break;
+    case float_relation_unordered:
+    default:
+        flags = PSTATE_C | PSTATE_V;
+        break;
+    }
+    return flags;
+}
+
+uint64_t HELPER(vfp_cmps_a64)(float32 x, float32 y, void *fp_status)
+{
+    return float_rel_to_flags(float32_compare_quiet(x, y, fp_status));
+}
+
+uint64_t HELPER(vfp_cmpes_a64)(float32 x, float32 y, void *fp_status)
+{
+    return float_rel_to_flags(float32_compare(x, y, fp_status));
+}
+
+uint64_t HELPER(vfp_cmpd_a64)(float64 x, float64 y, void *fp_status)
+{
+    return float_rel_to_flags(float64_compare_quiet(x, y, fp_status));
+}
+
+uint64_t HELPER(vfp_cmped_a64)(float64 x, float64 y, void *fp_status)
+{
+    return float_rel_to_flags(float64_compare(x, y, fp_status));
+}

target-arm/helper-a64.h

@@ -22,3 +22,7 @@ DEF_HELPER_FLAGS_1(clz64, TCG_CALL_NO_RWG_SE, i64, i64)
 DEF_HELPER_FLAGS_1(cls64, TCG_CALL_NO_RWG_SE, i64, i64)
 DEF_HELPER_FLAGS_1(cls32, TCG_CALL_NO_RWG_SE, i32, i32)
 DEF_HELPER_FLAGS_1(rbit64, TCG_CALL_NO_RWG_SE, i64, i64)
+DEF_HELPER_3(vfp_cmps_a64, i64, f32, f32, ptr)
+DEF_HELPER_3(vfp_cmpes_a64, i64, f32, f32, ptr)
+DEF_HELPER_3(vfp_cmpd_a64, i64, f64, f64, ptr)
+DEF_HELPER_3(vfp_cmped_a64, i64, f64, f64, ptr)

target-arm/translate-a64.c

@@ -3186,6 +3186,54 @@ static void disas_data_proc_reg(DisasContext *s, uint32_t insn)
     }
 }
 
+static void handle_fp_compare(DisasContext *s, bool is_double,
+                              unsigned int rn, unsigned int rm,
+                              bool cmp_with_zero, bool signal_all_nans)
+{
+    TCGv_i64 tcg_flags = tcg_temp_new_i64();
+    TCGv_ptr fpst = get_fpstatus_ptr();
+
+    if (is_double) {
+        TCGv_i64 tcg_vn, tcg_vm;
+
+        tcg_vn = read_fp_dreg(s, rn);
+        if (cmp_with_zero) {
+            tcg_vm = tcg_const_i64(0);
+        } else {
+            tcg_vm = read_fp_dreg(s, rm);
+        }
+        if (signal_all_nans) {
+            gen_helper_vfp_cmped_a64(tcg_flags, tcg_vn, tcg_vm, fpst);
+        } else {
+            gen_helper_vfp_cmpd_a64(tcg_flags, tcg_vn, tcg_vm, fpst);
+        }
+        tcg_temp_free_i64(tcg_vn);
+        tcg_temp_free_i64(tcg_vm);
+    } else {
+        TCGv_i32 tcg_vn, tcg_vm;
+
+        tcg_vn = read_fp_sreg(s, rn);
+        if (cmp_with_zero) {
+            tcg_vm = tcg_const_i32(0);
+        } else {
+            tcg_vm = read_fp_sreg(s, rm);
+        }
+        if (signal_all_nans) {
+            gen_helper_vfp_cmpes_a64(tcg_flags, tcg_vn, tcg_vm, fpst);
+        } else {
+            gen_helper_vfp_cmps_a64(tcg_flags, tcg_vn, tcg_vm, fpst);
+        }
+        tcg_temp_free_i32(tcg_vn);
+        tcg_temp_free_i32(tcg_vm);
+    }
+
+    tcg_temp_free_ptr(fpst);
+
+    gen_set_nzcv(tcg_flags);
+
+    tcg_temp_free_i64(tcg_flags);
+}
+
 /* C3.6.22 Floating point compare
  *   31  30  29 28       24 23  22  21 20  16 15 14 13  10    9    5 4     0
  * +---+---+---+-----------+------+---+------+-----+---------+------+-------+
@@ -3194,7 +3242,22 @@ static void disas_data_proc_reg(DisasContext *s, uint32_t insn)
  */
 static void disas_fp_compare(DisasContext *s, uint32_t insn)
 {
-    unsupported_encoding(s, insn);
+    unsigned int mos, type, rm, op, rn, opc, op2r;
+
+    mos = extract32(insn, 29, 3);
+    type = extract32(insn, 22, 2); /* 0 = single, 1 = double */
+    rm = extract32(insn, 16, 5);
+    op = extract32(insn, 14, 2);
+    rn = extract32(insn, 5, 5);
+    opc = extract32(insn, 3, 2);
+    op2r = extract32(insn, 0, 3);
+
+    if (mos || op || op2r || type > 1) {
+        unallocated_encoding(s);
+        return;
+    }
+
+    handle_fp_compare(s, type, rn, rm, opc & 1, opc & 2);
 }
 
 /* C3.6.23 Floating point conditional compare