[RFC PATCH] target/i386: for maximum rounding precision for fildll

[Alex Bennée]

The instruction description says "It is loaded without rounding
errors." which implies we should have the widest rounding mode
possible.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/888
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 target/i386/tcg/fpu_helper.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/target/i386/tcg/fpu_helper.c b/target/i386/tcg/fpu_helper.c
index cdd8e9f947..d986fd5792 100644
--- a/target/i386/tcg/fpu_helper.c
+++ b/target/i386/tcg/fpu_helper.c
@@ -250,11 +250,15 @@ void helper_fildl_ST0(CPUX86State *env, int32_t val)
 void helper_fildll_ST0(CPUX86State *env, int64_t val)
 {
     int new_fpstt;
+    FloatX80RoundPrec old = get_floatx80_rounding_precision(&env->fp_status);
+    set_floatx80_rounding_precision(floatx80_precision_x, &env->fp_status);
 
     new_fpstt = (env->fpstt - 1) & 7;
     env->fpregs[new_fpstt].d = int64_to_floatx80(val, &env->fp_status);
     env->fpstt = new_fpstt;
     env->fptags[new_fpstt] = 0; /* validate stack entry */
+
+    set_floatx80_rounding_precision(old, &env->fp_status);
 }
 
 uint32_t helper_fsts_ST0(CPUX86State *env)
-- 
2.30.2