target/i386: introduce function to set rounding mode from FPCW or MXCSR bits

VROUND, FSTCW and STMXCSR all have to perform the same conversion from
x86 rounding modes to softfloat constants.  Since the ISA is consistent
on the meaning of the two-bit rounding modes, extract the common code
into a wrapper for set_float_rounding_mode.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2 files changed, 25 insertions, 95 deletions

diff --git a/target/i386/ops_sse.h b/target/i386/ops_sse.h
index d35fc15c65..0799712f6e 100644
--- a/target/i386/ops_sse.h
+++ b/target/i386/ops_sse.h
@@ -1684,20 +1684,7 @@ void glue(helper_roundps, SUFFIX)(CPUX86State *env, Reg *d, Reg *s,
 
     prev_rounding_mode = env->sse_status.float_rounding_mode;
     if (!(mode & (1 << 2))) {
-        switch (mode & 3) {
-        case 0:
-            set_float_rounding_mode(float_round_nearest_even, &env->sse_status);
-            break;
-        case 1:
-            set_float_rounding_mode(float_round_down, &env->sse_status);
-            break;
-        case 2:
-            set_float_rounding_mode(float_round_up, &env->sse_status);
-            break;
-        case 3:
-            set_float_rounding_mode(float_round_to_zero, &env->sse_status);
-            break;
-        }
+        set_x86_rounding_mode(mode & 3, &env->sse_status);
     }
 
     for (i = 0; i < 2 << SHIFT; i++) {
@@ -1721,20 +1708,7 @@ void glue(helper_roundpd, SUFFIX)(CPUX86State *env, Reg *d, Reg *s,
 
     prev_rounding_mode = env->sse_status.float_rounding_mode;
     if (!(mode & (1 << 2))) {
-        switch (mode & 3) {
-        case 0:
-            set_float_rounding_mode(float_round_nearest_even, &env->sse_status);
-            break;
-        case 1:
-            set_float_rounding_mode(float_round_down, &env->sse_status);
-            break;
-        case 2:
-            set_float_rounding_mode(float_round_up, &env->sse_status);
-            break;
-        case 3:
-            set_float_rounding_mode(float_round_to_zero, &env->sse_status);
-            break;
-        }
+        set_x86_rounding_mode(mode & 3, &env->sse_status);
     }
 
     for (i = 0; i < 1 << SHIFT; i++) {
@@ -1759,20 +1733,7 @@ void glue(helper_roundss, SUFFIX)(CPUX86State *env, Reg *d, Reg *v, Reg *s,
 
     prev_rounding_mode = env->sse_status.float_rounding_mode;
     if (!(mode & (1 << 2))) {
-        switch (mode & 3) {
-        case 0:
-            set_float_rounding_mode(float_round_nearest_even, &env->sse_status);
-            break;
-        case 1:
-            set_float_rounding_mode(float_round_down, &env->sse_status);
-            break;
-        case 2:
-            set_float_rounding_mode(float_round_up, &env->sse_status);
-            break;
-        case 3:
-            set_float_rounding_mode(float_round_to_zero, &env->sse_status);
-            break;
-        }
+        set_x86_rounding_mode(mode & 3, &env->sse_status);
     }
 
     d->ZMM_S(0) = float32_round_to_int(s->ZMM_S(0), &env->sse_status);
@@ -1797,20 +1758,7 @@ void glue(helper_roundsd, SUFFIX)(CPUX86State *env, Reg *d, Reg *v, Reg *s,
 
     prev_rounding_mode = env->sse_status.float_rounding_mode;
     if (!(mode & (1 << 2))) {
-        switch (mode & 3) {
-        case 0:
-            set_float_rounding_mode(float_round_nearest_even, &env->sse_status);
-            break;
-        case 1:
-            set_float_rounding_mode(float_round_down, &env->sse_status);
-            break;
-        case 2:
-            set_float_rounding_mode(float_round_up, &env->sse_status);
-            break;
-        case 3:
-            set_float_rounding_mode(float_round_to_zero, &env->sse_status);
-            break;
-        }
+        set_x86_rounding_mode(mode & 3, &env->sse_status);
     }
 
     d->ZMM_D(0) = float64_round_to_int(s->ZMM_D(0), &env->sse_status);
diff --git a/target/i386/tcg/fpu_helper.c b/target/i386/tcg/fpu_helper.c
index a6a90a1817..6f3741b635 100644
--- a/target/i386/tcg/fpu_helper.c
+++ b/target/i386/tcg/fpu_helper.c
@@ -32,7 +32,8 @@
 #define ST(n)  (env->fpregs[(env->fpstt + (n)) & 7].d)
 #define ST1    ST(1)
 
-#define FPU_RC_MASK         0xc00
+#define FPU_RC_SHIFT        10
+#define FPU_RC_MASK         (3 << FPU_RC_SHIFT)
 #define FPU_RC_NEAR         0x000
 #define FPU_RC_DOWN         0x400
 #define FPU_RC_UP           0x800
@@ -685,28 +686,26 @@ uint32_t helper_fnstcw(CPUX86State *env)
     return env->fpuc;
 }
 
+static void set_x86_rounding_mode(unsigned mode, float_status *status)
+{
+    static FloatRoundMode x86_round_mode[4] = {
+        float_round_nearest_even,
+        float_round_down,
+        float_round_up,
+        float_round_to_zero
+    };
+    assert(mode < ARRAY_SIZE(x86_round_mode));
+    set_float_rounding_mode(x86_round_mode[mode], status);
+}
+
 void update_fp_status(CPUX86State *env)
 {
-    FloatRoundMode rnd_mode;
+    int rnd_mode;
     FloatX80RoundPrec rnd_prec;
 
     /* set rounding mode */
-    switch (env->fpuc & FPU_RC_MASK) {
-    default:
-    case FPU_RC_NEAR:
-        rnd_mode = float_round_nearest_even;
-        break;
-    case FPU_RC_DOWN:
-        rnd_mode = float_round_down;
-        break;
-    case FPU_RC_UP:
-        rnd_mode = float_round_up;
-        break;
-    case FPU_RC_CHOP:
-        rnd_mode = float_round_to_zero;
-        break;
-    }
-    set_float_rounding_mode(rnd_mode, &env->fp_status);
+    rnd_mode = (env->fpuc & FPU_RC_MASK) >> FPU_RC_SHIFT;
+    set_x86_rounding_mode(rnd_mode, &env->fp_status);
 
     switch ((env->fpuc >> 8) & 3) {
     case 0:
@@ -3038,11 +3037,8 @@ void helper_xsetbv(CPUX86State *env, uint32_t ecx, uint64_t mask)
 /* XXX: optimize by storing fptt and fptags in the static cpu state */
 
 #define SSE_DAZ             0x0040
-#define SSE_RC_MASK         0x6000
-#define SSE_RC_NEAR         0x0000
-#define SSE_RC_DOWN         0x2000
-#define SSE_RC_UP           0x4000
-#define SSE_RC_CHOP         0x6000
+#define SSE_RC_SHIFT        13
+#define SSE_RC_MASK         (3 << SSE_RC_SHIFT)
 #define SSE_FZ              0x8000
 
 void update_mxcsr_status(CPUX86State *env)
@@ -3051,22 +3047,8 @@ void update_mxcsr_status(CPUX86State *env)
     int rnd_type;
 
     /* set rounding mode */
-    switch (mxcsr & SSE_RC_MASK) {
-    default:
-    case SSE_RC_NEAR:
-        rnd_type = float_round_nearest_even;
-        break;
-    case SSE_RC_DOWN:
-        rnd_type = float_round_down;
-        break;
-    case SSE_RC_UP:
-        rnd_type = float_round_up;
-        break;
-    case SSE_RC_CHOP:
-        rnd_type = float_round_to_zero;
-        break;
-    }
-    set_float_rounding_mode(rnd_type, &env->sse_status);
+    rnd_type = (mxcsr & SSE_RC_MASK) >> SSE_RC_SHIFT;
+    set_x86_rounding_mode(rnd_type, &env->sse_status);
 
     /* Set exception flags.  */
     set_float_exception_flags((mxcsr & FPUS_IE ? float_flag_invalid : 0) |