target/m68k: implement flognp1

Using a local m68k floatx80_lognp1()
[copied from previous:
Written by Andreas Grabher for Previous, NeXT Computer Emulator.]

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20180305203910.10391-3-laurent@vivier.eu>

1 files changed, 216 insertions, 0 deletions

diff --git a/target/m68k/softfloat.c b/target/m68k/softfloat.c
index 55eb7a260a..834db12964 100644
--- a/target/m68k/softfloat.c
+++ b/target/m68k/softfloat.c
@@ -21,6 +21,7 @@
 #include "qemu/osdep.h"
 #include "softfloat.h"
 #include "fpu/softfloat-macros.h"
+#include "softfloat_fpsp_tables.h"
 
 static floatx80 propagateFloatx80NaNOneArg(floatx80 a, float_status *status)
 {
@@ -274,3 +275,218 @@ floatx80 floatx80_move(floatx80 a, float_status *status)
     return roundAndPackFloatx80(status->floatx80_rounding_precision, aSign,
                                 aExp, aSig, 0, status);
 }
+
+/*----------------------------------------------------------------------------
+| Algorithms for transcendental functions supported by MC68881 and MC68882
+| mathematical coprocessors. The functions are derived from FPSP library.
+*----------------------------------------------------------------------------*/
+
+#define one_exp     0x3FFF
+#define one_sig     LIT64(0x8000000000000000)
+
+/*----------------------------------------------------------------------------
+ | Function for compactifying extended double-precision floating point values.
+ *----------------------------------------------------------------------------*/
+
+static int32_t floatx80_make_compact(int32_t aExp, uint64_t aSig)
+{
+    return (aExp << 16) | (aSig >> 48);
+}
+
+/*----------------------------------------------------------------------------
+ | Log base e of x plus 1
+ *----------------------------------------------------------------------------*/
+
+floatx80 floatx80_lognp1(floatx80 a, float_status *status)
+{
+    flag aSign;
+    int32_t aExp;
+    uint64_t aSig, fSig;
+
+    int8_t user_rnd_mode, user_rnd_prec;
+
+    int32_t compact, j, k;
+    floatx80 fp0, fp1, fp2, fp3, f, logof2, klog2, saveu;
+
+    aSig = extractFloatx80Frac(a);
+    aExp = extractFloatx80Exp(a);
+    aSign = extractFloatx80Sign(a);
+
+    if (aExp == 0x7FFF) {
+        if ((uint64_t) (aSig << 1)) {
+            propagateFloatx80NaNOneArg(a, status);
+        }
+        if (aSign) {
+            float_raise(float_flag_invalid, status);
+            return floatx80_default_nan(status);
+        }
+        return packFloatx80(0, floatx80_infinity.high, floatx80_infinity.low);
+    }
+
+    if (aExp == 0 && aSig == 0) {
+        return packFloatx80(aSign, 0, 0);
+    }
+
+    if (aSign && aExp >= one_exp) {
+        if (aExp == one_exp && aSig == one_sig) {
+            float_raise(float_flag_divbyzero, status);
+            packFloatx80(aSign, floatx80_infinity.high, floatx80_infinity.low);
+        }
+        float_raise(float_flag_invalid, status);
+        return floatx80_default_nan(status);
+    }
+
+    if (aExp < 0x3f99 || (aExp == 0x3f99 && aSig == one_sig)) {
+        /* <= min threshold */
+        float_raise(float_flag_inexact, status);
+        return floatx80_move(a, status);
+    }
+
+    user_rnd_mode = status->float_rounding_mode;
+    user_rnd_prec = status->floatx80_rounding_precision;
+    status->float_rounding_mode = float_round_nearest_even;
+    status->floatx80_rounding_precision = 80;
+
+    compact = floatx80_make_compact(aExp, aSig);
+
+    fp0 = a; /* Z */
+    fp1 = a;
+
+    fp0 = floatx80_add(fp0, float32_to_floatx80(make_float32(0x3F800000),
+                       status), status); /* X = (1+Z) */
+
+    aExp = extractFloatx80Exp(fp0);
+    aSig = extractFloatx80Frac(fp0);
+
+    compact = floatx80_make_compact(aExp, aSig);
+
+    if (compact < 0x3FFE8000 || compact > 0x3FFFC000) {
+        /* |X| < 1/2 or |X| > 3/2 */
+        k = aExp - 0x3FFF;
+        fp1 = int32_to_floatx80(k, status);
+
+        fSig = (aSig & LIT64(0xFE00000000000000)) | LIT64(0x0100000000000000);
+        j = (fSig >> 56) & 0x7E; /* DISPLACEMENT FOR 1/F */
+
+        f = packFloatx80(0, 0x3FFF, fSig); /* F */
+        fp0 = packFloatx80(0, 0x3FFF, aSig); /* Y */
+
+        fp0 = floatx80_sub(fp0, f, status); /* Y-F */
+
+    lp1cont1:
+        /* LP1CONT1 */
+        fp0 = floatx80_mul(fp0, log_tbl[j], status); /* FP0 IS U = (Y-F)/F */
+        logof2 = packFloatx80(0, 0x3FFE, LIT64(0xB17217F7D1CF79AC));
+        klog2 = floatx80_mul(fp1, logof2, status); /* FP1 IS K*LOG2 */
+        fp2 = floatx80_mul(fp0, fp0, status); /* FP2 IS V=U*U */
+
+        fp3 = fp2;
+        fp1 = fp2;
+
+        fp1 = floatx80_mul(fp1, float64_to_floatx80(
+                           make_float64(0x3FC2499AB5E4040B), status),
+                           status); /* V*A6 */
+        fp2 = floatx80_mul(fp2, float64_to_floatx80(
+                           make_float64(0xBFC555B5848CB7DB), status),
+                           status); /* V*A5 */
+        fp1 = floatx80_add(fp1, float64_to_floatx80(
+                           make_float64(0x3FC99999987D8730), status),
+                           status); /* A4+V*A6 */
+        fp2 = floatx80_add(fp2, float64_to_floatx80(
+                           make_float64(0xBFCFFFFFFF6F7E97), status),
+                           status); /* A3+V*A5 */
+        fp1 = floatx80_mul(fp1, fp3, status); /* V*(A4+V*A6) */
+        fp2 = floatx80_mul(fp2, fp3, status); /* V*(A3+V*A5) */
+        fp1 = floatx80_add(fp1, float64_to_floatx80(
+                           make_float64(0x3FD55555555555A4), status),
+                           status); /* A2+V*(A4+V*A6) */
+        fp2 = floatx80_add(fp2, float64_to_floatx80(
+                           make_float64(0xBFE0000000000008), status),
+                           status); /* A1+V*(A3+V*A5) */
+        fp1 = floatx80_mul(fp1, fp3, status); /* V*(A2+V*(A4+V*A6)) */
+        fp2 = floatx80_mul(fp2, fp3, status); /* V*(A1+V*(A3+V*A5)) */
+        fp1 = floatx80_mul(fp1, fp0, status); /* U*V*(A2+V*(A4+V*A6)) */
+        fp0 = floatx80_add(fp0, fp2, status); /* U+V*(A1+V*(A3+V*A5)) */
+
+        fp1 = floatx80_add(fp1, log_tbl[j + 1],
+                           status); /* LOG(F)+U*V*(A2+V*(A4+V*A6)) */
+        fp0 = floatx80_add(fp0, fp1, status); /* FP0 IS LOG(F) + LOG(1+U) */
+
+        status->float_rounding_mode = user_rnd_mode;
+        status->floatx80_rounding_precision = user_rnd_prec;
+
+        a = floatx80_add(fp0, klog2, status);
+
+        float_raise(float_flag_inexact, status);
+
+        return a;
+    } else if (compact < 0x3FFEF07D || compact > 0x3FFF8841) {
+        /* |X| < 1/16 or |X| > -1/16 */
+        /* LP1CARE */
+        fSig = (aSig & LIT64(0xFE00000000000000)) | LIT64(0x0100000000000000);
+        f = packFloatx80(0, 0x3FFF, fSig); /* F */
+        j = (fSig >> 56) & 0x7E; /* DISPLACEMENT FOR 1/F */
+
+        if (compact >= 0x3FFF8000) { /* 1+Z >= 1 */
+            /* KISZERO */
+            fp0 = floatx80_sub(float32_to_floatx80(make_float32(0x3F800000),
+                               status), f, status); /* 1-F */
+            fp0 = floatx80_add(fp0, fp1, status); /* FP0 IS Y-F = (1-F)+Z */
+            fp1 = packFloatx80(0, 0, 0); /* K = 0 */
+        } else {
+            /* KISNEG */
+            fp0 = floatx80_sub(float32_to_floatx80(make_float32(0x40000000),
+                               status), f, status); /* 2-F */
+            fp1 = floatx80_add(fp1, fp1, status); /* 2Z */
+            fp0 = floatx80_add(fp0, fp1, status); /* FP0 IS Y-F = (2-F)+2Z */
+            fp1 = packFloatx80(1, one_exp, one_sig); /* K = -1 */
+        }
+        goto lp1cont1;
+    } else {
+        /* LP1ONE16 */
+        fp1 = floatx80_add(fp1, fp1, status); /* FP1 IS 2Z */
+        fp0 = floatx80_add(fp0, float32_to_floatx80(make_float32(0x3F800000),
+                           status), status); /* FP0 IS 1+X */
+
+        /* LP1CONT2 */
+        fp1 = floatx80_div(fp1, fp0, status); /* U */
+        saveu = fp1;
+        fp0 = floatx80_mul(fp1, fp1, status); /* FP0 IS V = U*U */
+        fp1 = floatx80_mul(fp0, fp0, status); /* FP1 IS W = V*V */
+
+        fp3 = float64_to_floatx80(make_float64(0x3F175496ADD7DAD6),
+                                  status); /* B5 */
+        fp2 = float64_to_floatx80(make_float64(0x3F3C71C2FE80C7E0),
+                                  status); /* B4 */
+        fp3 = floatx80_mul(fp3, fp1, status); /* W*B5 */
+        fp2 = floatx80_mul(fp2, fp1, status); /* W*B4 */
+        fp3 = floatx80_add(fp3, float64_to_floatx80(
+                           make_float64(0x3F624924928BCCFF), status),
+                           status); /* B3+W*B5 */
+        fp2 = floatx80_add(fp2, float64_to_floatx80(
+                           make_float64(0x3F899999999995EC), status),
+                           status); /* B2+W*B4 */
+        fp1 = floatx80_mul(fp1, fp3, status); /* W*(B3+W*B5) */
+        fp2 = floatx80_mul(fp2, fp0, status); /* V*(B2+W*B4) */
+        fp1 = floatx80_add(fp1, float64_to_floatx80(
+                           make_float64(0x3FB5555555555555), status),
+                           status); /* B1+W*(B3+W*B5) */
+
+        fp0 = floatx80_mul(fp0, saveu, status); /* FP0 IS U*V */
+        fp1 = floatx80_add(fp1, fp2,
+                           status); /* B1+W*(B3+W*B5) + V*(B2+W*B4) */
+        fp0 = floatx80_mul(fp0, fp1,
+                           status); /* U*V*([B1+W*(B3+W*B5)] + [V*(B2+W*B4)]) */
+
+        status->float_rounding_mode = user_rnd_mode;
+        status->floatx80_rounding_precision = user_rnd_prec;
+
+        a = floatx80_add(fp0, saveu, status);
+
+        /*if (!floatx80_is_zero(a)) { */
+            float_raise(float_flag_inexact, status);
+        /*} */
+
+        return a;
+    }
+}