[PATCH 7/7] target/i386: reimplement fprem using floatx80 operations

[Joseph Myers]

The x87 fprem emulation is currently based around conversion to
double, which is inherently unsuitable for a good emulation of any
floatx80 operation.  Reimplement using the soft-float floatx80
remainder operations.

Signed-off-by: Joseph Myers <joseph@codesourcery.com>
---
 target/i386/fpu_helper.c | 58 +---------------------------------------
 1 file changed, 1 insertion(+), 57 deletions(-)

diff --git a/target/i386/fpu_helper.c b/target/i386/fpu_helper.c
index bab35e00a0..d2fc2c1dde 100644
--- a/target/i386/fpu_helper.c
+++ b/target/i386/fpu_helper.c
@@ -989,63 +989,7 @@ void helper_fprem1(CPUX86State *env)
 
 void helper_fprem(CPUX86State *env)
 {
-    double st0, st1, dblq, fpsrcop, fptemp;
-    CPU_LDoubleU fpsrcop1, fptemp1;
-    int expdif;
-    signed long long int q;
-
-    st0 = floatx80_to_double(env, ST0);
-    st1 = floatx80_to_double(env, ST1);
-
-    if (isinf(st0) || isnan(st0) || isnan(st1) || (st1 == 0.0)) {
-        ST0 = double_to_floatx80(env, 0.0 / 0.0); /* NaN */
-        env->fpus &= ~0x4700; /* (C3,C2,C1,C0) <-- 0000 */
-        return;
-    }
-
-    fpsrcop = st0;
-    fptemp = st1;
-    fpsrcop1.d = ST0;
-    fptemp1.d = ST1;
-    expdif = EXPD(fpsrcop1) - EXPD(fptemp1);
-
-    if (expdif < 0) {
-        /* optimisation? taken from the AMD docs */
-        env->fpus &= ~0x4700; /* (C3,C2,C1,C0) <-- 0000 */
-        /* ST0 is unchanged */
-        return;
-    }
-
-    if (expdif < 53) {
-        dblq = fpsrcop / fptemp; /* ST0 / ST1 */
-        /* round dblq towards zero */
-        dblq = (dblq < 0.0) ? ceil(dblq) : floor(dblq);
-        st0 = fpsrcop - fptemp * dblq; /* fpsrcop is ST0 */
-
-        /* convert dblq to q by truncating towards zero */
-        if (dblq < 0.0) {
-            q = (signed long long int)(-dblq);
-        } else {
-            q = (signed long long int)dblq;
-        }
-
-        env->fpus &= ~0x4700; /* (C3,C2,C1,C0) <-- 0000 */
-        /* (C0,C3,C1) <-- (q2,q1,q0) */
-        env->fpus |= (q & 0x4) << (8 - 2);  /* (C0) <-- q2 */
-        env->fpus |= (q & 0x2) << (14 - 1); /* (C3) <-- q1 */
-        env->fpus |= (q & 0x1) << (9 - 0);  /* (C1) <-- q0 */
-    } else {
-        int N = 32 + (expdif % 32); /* as per AMD docs */
-
-        env->fpus |= 0x400;  /* C2 <-- 1 */
-        fptemp = pow(2.0, (double)(expdif - N));
-        fpsrcop = (st0 / st1) / fptemp;
-        /* fpsrcop = integer obtained by chopping */
-        fpsrcop = (fpsrcop < 0.0) ?
-                  -(floor(fabs(fpsrcop))) : floor(fpsrcop);
-        st0 -= (st1 * fpsrcop * fptemp);
-    }
-    ST0 = double_to_floatx80(env, st0);
+    helper_fprem_common(env, true);
 }
 
 void helper_fyl2xp1(CPUX86State *env)
-- 
2.17.1


-- 
Joseph S. Myers
joseph@codesourcery.com