target-m68k: add FPCR and FPSR

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Message-Id: <20170620205121.26515-6-laurent@vivier.eu>

1 files changed, 101 insertions, 16 deletions

diff --git a/target/m68k/fpu_helper.c b/target/m68k/fpu_helper.c
index f4d38216d2..a9e17f5e98 100644
--- a/target/m68k/fpu_helper.c
+++ b/target/m68k/fpu_helper.c
@@ -58,9 +58,74 @@ void HELPER(firound)(CPUM68KState *env, FPReg *res, FPReg *val)
     res->d = floatx80_round_to_int(val->d, &env->fp_status);
 }
 
+static void m68k_restore_precision_mode(CPUM68KState *env)
+{
+    switch (env->fpcr & FPCR_PREC_MASK) {
+    case FPCR_PREC_X: /* extended */
+        set_floatx80_rounding_precision(80, &env->fp_status);
+        break;
+    case FPCR_PREC_S: /* single */
+        set_floatx80_rounding_precision(32, &env->fp_status);
+        break;
+    case FPCR_PREC_D: /* double */
+        set_floatx80_rounding_precision(64, &env->fp_status);
+        break;
+    case FPCR_PREC_U: /* undefined */
+    default:
+        break;
+    }
+}
+
+static void cf_restore_precision_mode(CPUM68KState *env)
+{
+    if (env->fpcr & FPCR_PREC_S) { /* single */
+        set_floatx80_rounding_precision(32, &env->fp_status);
+    } else { /* double */
+        set_floatx80_rounding_precision(64, &env->fp_status);
+    }
+}
+
+static void restore_rounding_mode(CPUM68KState *env)
+{
+    switch (env->fpcr & FPCR_RND_MASK) {
+    case FPCR_RND_N: /* round to nearest */
+        set_float_rounding_mode(float_round_nearest_even, &env->fp_status);
+        break;
+    case FPCR_RND_Z: /* round to zero */
+        set_float_rounding_mode(float_round_to_zero, &env->fp_status);
+        break;
+    case FPCR_RND_M: /* round toward minus infinity */
+        set_float_rounding_mode(float_round_down, &env->fp_status);
+        break;
+    case FPCR_RND_P: /* round toward positive infinity */
+        set_float_rounding_mode(float_round_up, &env->fp_status);
+        break;
+    }
+}
+
+void cpu_m68k_set_fpcr(CPUM68KState *env, uint32_t val)
+{
+    env->fpcr = val & 0xffff;
+
+    if (m68k_feature(env, M68K_FEATURE_CF_FPU)) {
+        cf_restore_precision_mode(env);
+    } else {
+        m68k_restore_precision_mode(env);
+    }
+    restore_rounding_mode(env);
+}
+
 void HELPER(fitrunc)(CPUM68KState *env, FPReg *res, FPReg *val)
 {
+    int rounding_mode = get_float_rounding_mode(&env->fp_status);
+    set_float_rounding_mode(float_round_to_zero, &env->fp_status);
     res->d = floatx80_round_to_int(val->d, &env->fp_status);
+    set_float_rounding_mode(rounding_mode, &env->fp_status);
+}
+
+void HELPER(set_fpcr)(CPUM68KState *env, uint32_t val)
+{
+    cpu_m68k_set_fpcr(env, val);
 }
 
 void HELPER(fsqrt)(CPUM68KState *env, FPReg *res, FPReg *val)
@@ -98,24 +163,44 @@ void HELPER(fdiv)(CPUM68KState *env, FPReg *res, FPReg *val0, FPReg *val1)
     res->d = floatx80_div(val1->d, val0->d, &env->fp_status);
 }
 
-void HELPER(fsub_cmp)(CPUM68KState *env, FPReg *res, FPReg *val0, FPReg *val1)
-{
-    /* ??? This may incorrectly raise exceptions.  */
-    /* ??? Should flush denormals to zero.  */
-    res->d = floatx80_sub(val0->d, val1->d, &env->fp_status);
-    if (floatx80_is_quiet_nan(res->d, &env->fp_status)) {
-        /* +/-inf compares equal against itself, but sub returns nan.  */
-        if (!floatx80_is_quiet_nan(val0->d, &env->fp_status)
-            && !floatx80_is_quiet_nan(val1->d, &env->fp_status)) {
-            res->d = floatx80_zero;
-            if (floatx80_lt_quiet(val0->d, res->d, &env->fp_status)) {
-                res->d = floatx80_chs(res->d);
-            }
-        }
+static int float_comp_to_cc(int float_compare)
+{
+    switch (float_compare) {
+    case float_relation_equal:
+        return FPSR_CC_Z;
+    case float_relation_less:
+        return FPSR_CC_N;
+    case float_relation_unordered:
+        return FPSR_CC_A;
+    case float_relation_greater:
+        return 0;
+    default:
+        g_assert_not_reached();
     }
 }
 
-uint32_t HELPER(fcompare)(CPUM68KState *env, FPReg *val)
+void HELPER(fcmp)(CPUM68KState *env, FPReg *val0, FPReg *val1)
 {
-    return floatx80_compare_quiet(val->d, floatx80_zero, &env->fp_status);
+    int float_compare;
+
+    float_compare = floatx80_compare(val1->d, val0->d, &env->fp_status);
+    env->fpsr = (env->fpsr & ~FPSR_CC_MASK) | float_comp_to_cc(float_compare);
+}
+
+void HELPER(ftst)(CPUM68KState *env, FPReg *val)
+{
+    uint32_t cc = 0;
+
+    if (floatx80_is_neg(val->d)) {
+        cc |= FPSR_CC_N;
+    }
+
+    if (floatx80_is_any_nan(val->d)) {
+        cc |= FPSR_CC_A;
+    } else if (floatx80_is_infinity(val->d)) {
+        cc |= FPSR_CC_I;
+    } else if (floatx80_is_zero(val->d)) {
+        cc |= FPSR_CC_Z;
+    }
+    env->fpsr = (env->fpsr & ~FPSR_CC_MASK) | cc;
 }