* [PATCH] target/i386: check for empty register in FXAM
@ 2020-02-21 16:20 Paolo Bonzini
0 siblings, 0 replies; only message in thread
From: Paolo Bonzini @ 2020-02-21 16:20 UTC (permalink / raw)
To: qemu-devel; +Cc: chengang
The fxam instruction returns the wrong result after fdecstp or after
an underflow. Check fptags to handle this.
Reported-by: <chengang@emindsoft.com.cn>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
target/i386/fpu_helper.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/target/i386/fpu_helper.c b/target/i386/fpu_helper.c
index 99f28f267f..792a128a6d 100644
--- a/target/i386/fpu_helper.c
+++ b/target/i386/fpu_helper.c
@@ -991,7 +991,11 @@ void helper_fxam_ST0(CPUX86State *env)
env->fpus |= 0x200; /* C1 <-- 1 */
}
- /* XXX: test fptags too */
+ if (env->fptags[env->fpstt]) {
+ env->fpus |= 0x4100; /* Empty */
+ return;
+ }
+
expdif = EXPD(temp);
if (expdif == MAXEXPD) {
if (MANTD(temp) == 0x8000000000000000ULL) {
--
2.21.1
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