Commit 6802a4b23919 ("target/i386: clear C1 for all x87 compare
instructions") added an unconditional C1 clear to helper_fcomi_ST0_FT0()
and helper_fucomi_ST0_FT0(), based on the SDM listing "C1 Set to 0" under
FPU Flags Affected for FCOMI/FCOMIP/FUCOMI/FUCOMIP.
Testing on real x86-64 Intel and AMD hardware shows these instructions leave
C1 unchanged, unlike FCOM/FUCOM/FICOM. The SDM text appears to have been
carried over from the FCOM/FUCOM description.
Revert that part of the commit. The FCOM/FUCOM/FICOM changes are kept.
Fixes: 6802a4b23919 ("target/i386: clear C1 for all x87 compare instructions")
Signed-off-by: Simon Scherer <[email protected]>
---
This was caught before 6802a4b23919 landed. V3 [1] dropped the
fcomi/fucomi changes, but v2 was the version applied
[1] https://patchew.org/QEMU/[email protected]/
target/i386/tcg/fpu_helper.c | 4 ----
1 file changed, 4 deletions(-)
diff --git a/target/i386/tcg/fpu_helper.c b/target/i386/tcg/fpu_helper.c
index 54ff4fe31313..56d093da8c9a 100644
--- a/target/i386/tcg/fpu_helper.c
+++ b/target/i386/tcg/fpu_helper.c
@@ -565,8 +565,6 @@ void helper_fcomi_ST0_FT0(CPUX86State *env)
/* OF, SF, and AF are unconditionally cleared to 0 */
CC_SRC = fcomi_ccval[ret + 1];
CC_OP = CC_OP_EFLAGS;
- /* C1 is unconditionally cleared to 0 */
- env->fpus &= ~0x0200;
merge_exception_flags(env, old_flags);
}
@@ -579,8 +577,6 @@ void helper_fucomi_ST0_FT0(CPUX86State *env)
/* OF, SF, and AF are unconditionally cleared to 0 */
CC_SRC = fcomi_ccval[ret + 1];
CC_OP = CC_OP_EFLAGS;
- /* C1 is unconditionally cleared to 0 */
- env->fpus &= ~0x0200;
merge_exception_flags(env, old_flags);
}
--
2.53.0
