fpu: Add float64_to_int{32,64}_modulo

Add versions of float64_to_int* which do not saturate the result.

Reviewed-by: Christoph Muellner <christoph.muellner@vrull.eu>
Tested-by: Christoph Muellner <christoph.muellner@vrull.eu>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230527141910.1885950-2-richard.henderson@linaro.org>

1 files changed, 78 insertions, 0 deletions

diff --git a/fpu/softfloat-parts.c.inc b/fpu/softfloat-parts.c.inc
index 247400031c..527e15e6ab 100644
--- a/fpu/softfloat-parts.c.inc
+++ b/fpu/softfloat-parts.c.inc
@@ -1182,6 +1182,84 @@ static uint64_t partsN(float_to_uint)(FloatPartsN *p, FloatRoundMode rmode,
 }
 
 /*
+ * Like partsN(float_to_sint), except do not saturate the result.
+ * Instead, return the rounded unbounded precision two's compliment result,
+ * modulo 2**(bitsm1 + 1).
+ */
+static int64_t partsN(float_to_sint_modulo)(FloatPartsN *p,
+                                            FloatRoundMode rmode,
+                                            int bitsm1, float_status *s)
+{
+    int flags = 0;
+    uint64_t r;
+    bool overflow = false;
+
+    switch (p->cls) {
+    case float_class_snan:
+        flags |= float_flag_invalid_snan;
+        /* fall through */
+    case float_class_qnan:
+        flags |= float_flag_invalid;
+        r = 0;
+        break;
+
+    case float_class_inf:
+        overflow = true;
+        r = 0;
+        break;
+
+    case float_class_zero:
+        return 0;
+
+    case float_class_normal:
+        /* TODO: N - 2 is frac_size for rounding; could use input fmt. */
+        if (parts_round_to_int_normal(p, rmode, 0, N - 2)) {
+            flags = float_flag_inexact;
+        }
+
+        if (p->exp <= DECOMPOSED_BINARY_POINT) {
+            /*
+             * Because we rounded to integral, and exp < 64,
+             * we know frac_low is zero.
+             */
+            r = p->frac_hi >> (DECOMPOSED_BINARY_POINT - p->exp);
+            if (p->exp < bitsm1) {
+                /* Result in range. */
+            } else if (p->exp == bitsm1) {
+                /* The only in-range value is INT_MIN. */
+                overflow = !p->sign || p->frac_hi != DECOMPOSED_IMPLICIT_BIT;
+            } else {
+                overflow = true;
+            }
+        } else {
+            /* Overflow, but there might still be bits to return. */
+            int shl = p->exp - DECOMPOSED_BINARY_POINT;
+            if (shl < N) {
+                frac_shl(p, shl);
+                r = p->frac_hi;
+            } else {
+                r = 0;
+            }
+            overflow = true;
+        }
+
+        if (p->sign) {
+            r = -r;
+        }
+        break;
+
+    default:
+        g_assert_not_reached();
+    }
+
+    if (overflow) {
+        flags = float_flag_invalid | float_flag_invalid_cvti;
+    }
+    float_raise(flags, s);
+    return r;
+}
+
+/*
  * Integer to float conversions
  *
  * Returns the result of converting the two's complement integer `a'