softfloat: Move addsub_floats to softfloat-parts.c.inc

In preparation for implementing multiple sizes.  Rename to parts_addsub,
split out parts_add/sub_normal for future reuse with muladd.

Reviewed-by: Alex Bennée <[email protected]>
Signed-off-by: Richard Henderson <[email protected]>

fpu/softfloat-parts-addsub.c.inc

@@ -0,0 +1,62 @@
+/*
+ * Floating point arithmetic implementation
+ *
+ * The code in this source file is derived from release 2a of the SoftFloat
+ * IEC/IEEE Floating-point Arithmetic Package. Those parts of the code (and
+ * some later contributions) are provided under that license, as detailed below.
+ * It has subsequently been modified by contributors to the QEMU Project,
+ * so some portions are provided under:
+ *  the SoftFloat-2a license
+ *  the BSD license
+ *  GPL-v2-or-later
+ *
+ * Any future contributions to this file after December 1st 2014 will be
+ * taken to be licensed under the Softfloat-2a license unless specifically
+ * indicated otherwise.
+ */
+
+static void partsN(add_normal)(FloatPartsN *a, FloatPartsN *b)
+{
+    int exp_diff = a->exp - b->exp;
+
+    if (exp_diff > 0) {
+        frac_shrjam(b, exp_diff);
+    } else if (exp_diff < 0) {
+        frac_shrjam(a, -exp_diff);
+        a->exp = b->exp;
+    }
+
+    if (frac_add(a, a, b)) {
+        frac_shrjam(a, 1);
+        a->frac_hi |= DECOMPOSED_IMPLICIT_BIT;
+        a->exp += 1;
+    }
+}
+
+static bool partsN(sub_normal)(FloatPartsN *a, FloatPartsN *b)
+{
+    int exp_diff = a->exp - b->exp;
+    int shift;
+
+    if (exp_diff > 0) {
+        frac_shrjam(b, exp_diff);
+        frac_sub(a, a, b);
+    } else if (exp_diff < 0) {
+        a->exp = b->exp;
+        a->sign ^= 1;
+        frac_shrjam(a, -exp_diff);
+        frac_sub(a, b, a);
+    } else if (frac_sub(a, a, b)) {
+        /* Overflow means that A was less than B. */
+        frac_neg(a);
+        a->sign ^= 1;
+    }
+
+    shift = frac_normalize(a);
+    if (likely(shift < N)) {
+        a->exp -= shift;
+	return true;
+    }
+    a->cls = float_class_zero;
+    return false;
+}

fpu/softfloat-parts.c.inc

@@ -281,3 +281,84 @@ static void partsN(uncanon)(FloatPartsN *p, float_status *s,
     p->exp = exp;
     float_raise(flags, s);
 }
+
+/*
+ * Returns the result of adding or subtracting the values of the
+ * floating-point values `a' and `b'. The operation is performed
+ * according to the IEC/IEEE Standard for Binary Floating-Point
+ * Arithmetic.
+ */
+static FloatPartsN *partsN(addsub)(FloatPartsN *a, FloatPartsN *b,
+                                   float_status *s, bool subtract)
+{
+    bool b_sign = b->sign ^ subtract;
+    int ab_mask = float_cmask(a->cls) | float_cmask(b->cls);
+
+    if (a->sign != b_sign) {
+        /* Subtraction */
+        if (likely(ab_mask == float_cmask_normal)) {
+            if (parts_sub_normal(a, b)) {
+                return a;
+            }
+            /* Subtract was exact, fall through to set sign. */
+            ab_mask = float_cmask_zero;
+        }
+
+        if (ab_mask == float_cmask_zero) {
+            a->sign = s->float_rounding_mode == float_round_down;
+            return a;
+        }
+
+        if (unlikely(ab_mask & float_cmask_anynan)) {
+            goto p_nan;
+        }
+
+        if (ab_mask & float_cmask_inf) {
+            if (a->cls != float_class_inf) {
+                /* N - Inf */
+                goto return_b;
+            }
+            if (b->cls != float_class_inf) {
+                /* Inf - N */
+                return a;
+            }
+            /* Inf - Inf */
+            float_raise(float_flag_invalid, s);
+            parts_default_nan(a, s);
+            return a;
+        }
+    } else {
+        /* Addition */
+        if (likely(ab_mask == float_cmask_normal)) {
+            parts_add_normal(a, b);
+            return a;
+        }
+
+        if (ab_mask == float_cmask_zero) {
+            return a;
+        }
+
+        if (unlikely(ab_mask & float_cmask_anynan)) {
+            goto p_nan;
+        }
+
+        if (ab_mask & float_cmask_inf) {
+            a->cls = float_class_inf;
+            return a;
+        }
+    }
+
+    if (b->cls == float_class_zero) {
+        g_assert(a->cls == float_class_normal);
+        return a;
+    }
+
+    g_assert(a->cls == float_class_zero);
+    g_assert(b->cls == float_class_normal);
+ return_b:
+    b->sign = b_sign;
+    return b;
+
+ p_nan:
+    return parts_pick_nan(a, b, s);
+}