target/m68k: add fmod/frem

Using a local m68k floatx80_mod()
[copied from previous:
Written by Andreas Grabher for Previous, NeXT Computer Emulator.]

The quotient byte of the FPSR is updated with
the result of the operation.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20180224201802.911-3-laurent@vivier.eu>

target/m68k/softfloat.c

@@ -0,0 +1,105 @@
+/*
+ * Ported from a work by Andreas Grabher for Previous, NeXT Computer Emulator,
+ * derived from NetBSD M68040 FPSP functions,
+ * 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 will be taken to be licensed under
+ * the Softfloat-2a license unless specifically indicated otherwise.
+ */
+
+/* Portions of this work are licensed under the terms of the GNU GPL,
+ * version 2 or later. See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "softfloat.h"
+#include "fpu/softfloat-macros.h"
+
+/*----------------------------------------------------------------------------
+ | Returns the modulo remainder of the extended double-precision floating-point
+ | value `a' with respect to the corresponding value `b'.
+ *----------------------------------------------------------------------------*/
+
+floatx80 floatx80_mod(floatx80 a, floatx80 b, float_status *status)
+{
+    flag aSign, zSign;
+    int32_t aExp, bExp, expDiff;
+    uint64_t aSig0, aSig1, bSig;
+    uint64_t qTemp, term0, term1;
+
+    aSig0 = extractFloatx80Frac(a);
+    aExp = extractFloatx80Exp(a);
+    aSign = extractFloatx80Sign(a);
+    bSig = extractFloatx80Frac(b);
+    bExp = extractFloatx80Exp(b);
+
+    if (aExp == 0x7FFF) {
+        if ((uint64_t) (aSig0 << 1)
+            || ((bExp == 0x7FFF) && (uint64_t) (bSig << 1))) {
+            return propagateFloatx80NaN(a, b, status);
+        }
+        goto invalid;
+    }
+    if (bExp == 0x7FFF) {
+        if ((uint64_t) (bSig << 1)) {
+            return propagateFloatx80NaN(a, b, status);
+        }
+        return a;
+    }
+    if (bExp == 0) {
+        if (bSig == 0) {
+        invalid:
+            float_raise(float_flag_invalid, status);
+            return floatx80_default_nan(status);
+        }
+        normalizeFloatx80Subnormal(bSig, &bExp, &bSig);
+    }
+    if (aExp == 0) {
+        if ((uint64_t) (aSig0 << 1) == 0) {
+            return a;
+        }
+        normalizeFloatx80Subnormal(aSig0, &aExp, &aSig0);
+    }
+    bSig |= LIT64(0x8000000000000000);
+    zSign = aSign;
+    expDiff = aExp - bExp;
+    aSig1 = 0;
+    if (expDiff < 0) {
+        return a;
+    }
+    qTemp = (bSig <= aSig0);
+    if (qTemp) {
+        aSig0 -= bSig;
+    }
+    expDiff -= 64;
+    while (0 < expDiff) {
+        qTemp = estimateDiv128To64(aSig0, aSig1, bSig);
+        qTemp = (2 < qTemp) ? qTemp - 2 : 0;
+        mul64To128(bSig, qTemp, &term0, &term1);
+        sub128(aSig0, aSig1, term0, term1, &aSig0, &aSig1);
+        shortShift128Left(aSig0, aSig1, 62, &aSig0, &aSig1);
+    }
+    expDiff += 64;
+    if (0 < expDiff) {
+        qTemp = estimateDiv128To64(aSig0, aSig1, bSig);
+        qTemp = (2 < qTemp) ? qTemp - 2 : 0;
+        qTemp >>= 64 - expDiff;
+        mul64To128(bSig, qTemp << (64 - expDiff), &term0, &term1);
+        sub128(aSig0, aSig1, term0, term1, &aSig0, &aSig1);
+        shortShift128Left(0, bSig, 64 - expDiff, &term0, &term1);
+        while (le128(term0, term1, aSig0, aSig1)) {
+            ++qTemp;
+            sub128(aSig0, aSig1, term0, term1, &aSig0, &aSig1);
+        }
+    }
+    return
+        normalizeRoundAndPackFloatx80(
+            80, zSign, bExp + expDiff, aSig0, aSig1, status);
+}