target/m68k: add fscale, fgetman and fgetexp

Using local m68k floatx80_getman(), floatx80_getexp(), floatx80_scale()
[copied from previous:
Written by Andreas Grabher for Previous, NeXT Computer Emulator.]

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20180224201802.911-5-laurent@vivier.eu>

target/m68k/softfloat.c

@@ -22,6 +22,19 @@
 #include "softfloat.h"
 #include "fpu/softfloat-macros.h"
 
+static floatx80 propagateFloatx80NaNOneArg(floatx80 a, float_status *status)
+{
+    if (floatx80_is_signaling_nan(a, status)) {
+        float_raise(float_flag_invalid, status);
+    }
+
+    if (status->default_nan_mode) {
+        return floatx80_default_nan(status);
+    }
+
+    return floatx80_maybe_silence_nan(a, status);
+}
+
 /*----------------------------------------------------------------------------
  | Returns the modulo remainder of the extended double-precision floating-point
  | value `a' with respect to the corresponding value `b'.
@@ -103,3 +116,134 @@ floatx80 floatx80_mod(floatx80 a, floatx80 b, float_status *status)
         normalizeRoundAndPackFloatx80(
             80, zSign, bExp + expDiff, aSig0, aSig1, status);
 }
+
+/*----------------------------------------------------------------------------
+ | Returns the mantissa of the extended double-precision floating-point
+ | value `a'.
+ *----------------------------------------------------------------------------*/
+
+floatx80 floatx80_getman(floatx80 a, float_status *status)
+{
+    flag aSign;
+    int32_t aExp;
+    uint64_t aSig;
+
+    aSig = extractFloatx80Frac(a);
+    aExp = extractFloatx80Exp(a);
+    aSign = extractFloatx80Sign(a);
+
+    if (aExp == 0x7FFF) {
+        if ((uint64_t) (aSig << 1)) {
+            return propagateFloatx80NaNOneArg(a , status);
+        }
+        float_raise(float_flag_invalid , status);
+        return floatx80_default_nan(status);
+    }
+
+    if (aExp == 0) {
+        if (aSig == 0) {
+            return packFloatx80(aSign, 0, 0);
+        }
+        normalizeFloatx80Subnormal(aSig, &aExp, &aSig);
+    }
+
+    return roundAndPackFloatx80(status->floatx80_rounding_precision, aSign,
+                                0x3FFF, aSig, 0, status);
+}
+
+/*----------------------------------------------------------------------------
+ | Returns the exponent of the extended double-precision floating-point
+ | value `a' as an extended double-precision value.
+ *----------------------------------------------------------------------------*/
+
+floatx80 floatx80_getexp(floatx80 a, float_status *status)
+{
+    flag aSign;
+    int32_t aExp;
+    uint64_t aSig;
+
+    aSig = extractFloatx80Frac(a);
+    aExp = extractFloatx80Exp(a);
+    aSign = extractFloatx80Sign(a);
+
+    if (aExp == 0x7FFF) {
+        if ((uint64_t) (aSig << 1)) {
+            return propagateFloatx80NaNOneArg(a , status);
+        }
+        float_raise(float_flag_invalid , status);
+        return floatx80_default_nan(status);
+    }
+
+    if (aExp == 0) {
+        if (aSig == 0) {
+            return packFloatx80(aSign, 0, 0);
+        }
+        normalizeFloatx80Subnormal(aSig, &aExp, &aSig);
+    }
+
+    return int32_to_floatx80(aExp - 0x3FFF, status);
+}
+
+/*----------------------------------------------------------------------------
+ | Scales extended double-precision floating-point value in operand `a' by
+ | value `b'. The function truncates the value in the second operand 'b' to
+ | an integral value and adds that value to the exponent of the operand 'a'.
+ | The operation performed according to the IEC/IEEE Standard for Binary
+ | Floating-Point Arithmetic.
+ *----------------------------------------------------------------------------*/
+
+floatx80 floatx80_scale(floatx80 a, floatx80 b, float_status *status)
+{
+    flag aSign, bSign;
+    int32_t aExp, bExp, shiftCount;
+    uint64_t aSig, bSig;
+
+    aSig = extractFloatx80Frac(a);
+    aExp = extractFloatx80Exp(a);
+    aSign = extractFloatx80Sign(a);
+    bSig = extractFloatx80Frac(b);
+    bExp = extractFloatx80Exp(b);
+    bSign = extractFloatx80Sign(b);
+
+    if (bExp == 0x7FFF) {
+        if ((uint64_t) (bSig << 1) ||
+            ((aExp == 0x7FFF) && (uint64_t) (aSig << 1))) {
+            return propagateFloatx80NaN(a, b, status);
+        }
+        float_raise(float_flag_invalid , status);
+        return floatx80_default_nan(status);
+    }
+    if (aExp == 0x7FFF) {
+        if ((uint64_t) (aSig << 1)) {
+            return propagateFloatx80NaN(a, b, status);
+        }
+        return packFloatx80(aSign, floatx80_infinity.high,
+                            floatx80_infinity.low);
+    }
+    if (aExp == 0) {
+        if (aSig == 0) {
+            return packFloatx80(aSign, 0, 0);
+        }
+        if (bExp < 0x3FFF) {
+            return a;
+        }
+        normalizeFloatx80Subnormal(aSig, &aExp, &aSig);
+    }
+
+    if (bExp < 0x3FFF) {
+        return a;
+    }
+
+    if (0x400F < bExp) {
+        aExp = bSign ? -0x6001 : 0xE000;
+        return roundAndPackFloatx80(status->floatx80_rounding_precision,
+                                    aSign, aExp, aSig, 0, status);
+    }
+
+    shiftCount = 0x403E - bExp;
+    bSig >>= shiftCount;
+    aExp = bSign ? (aExp - bSig) : (aExp + bSig);
+
+    return roundAndPackFloatx80(status->floatx80_rounding_precision,
+                                aSign, aExp, aSig, 0, status);
+}