diff mbox series

[75/76] target/i386: Wire up MXCSR.DE and FPUS.DE correctly

Message ID 20250124162836.2332150-76-peter.maydell@linaro.org (mailing list archive)
State New
Headers show
Series target/arm: Implement FEAT_AFP and FEAT_RPRES | expand

Commit Message

Peter Maydell Jan. 24, 2025, 4:28 p.m. UTC 
The x86 DE bit in the FPU and MXCSR status is supposed to be set
when an input denormal is consumed. We didn't previously report
this from softfloat, so the x86 code either simply didn't set
the DE bit or else incorrectly wired it up to denormal_flushed,
depending on which register you looked at.

Now we have input_denormal_used we can wire up these DE bits
with the semantics they are supposed to have.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/i386/tcg/fpu_helper.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

Comments

Richard Henderson Jan. 26, 2025, 1:31 p.m. UTC | #1 
On 1/24/25 08:28, Peter Maydell wrote:
> The x86 DE bit in the FPU and MXCSR status is supposed to be set
> when an input denormal is consumed. We didn't previously report
> this from softfloat, so the x86 code either simply didn't set
> the DE bit or else incorrectly wired it up to denormal_flushed,
> depending on which register you looked at.
> 
> Now we have input_denormal_used we can wire up these DE bits
> with the semantics they are supposed to have.
> 
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
>   target/i386/tcg/fpu_helper.c | 11 +++--------
>   1 file changed, 3 insertions(+), 8 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~
diff mbox series

Patch

diff --git a/target/i386/tcg/fpu_helper.c b/target/i386/tcg/fpu_helper.c
index 97b46307d56..fd1cd823e9e 100644
--- a/target/i386/tcg/fpu_helper.c
+++ b/target/i386/tcg/fpu_helper.c
@@ -215,7 +215,7 @@  static void merge_exception_flags(CPUX86State *env, int old_flags)
                        (new_flags & float_flag_overflow ? FPUS_OE : 0) |
                        (new_flags & float_flag_underflow ? FPUS_UE : 0) |
                        (new_flags & float_flag_inexact ? FPUS_PE : 0) |
-                       (new_flags & float_flag_input_denormal_flushed ? FPUS_DE : 0)));
+                       (new_flags & float_flag_input_denormal_used ? FPUS_DE : 0)));
 }
 
 static inline floatx80 helper_fdiv(CPUX86State *env, floatx80 a, floatx80 b)
@@ -3251,6 +3251,7 @@  void update_mxcsr_status(CPUX86State *env)
 
     /* Set exception flags.  */
     set_float_exception_flags((mxcsr & FPUS_IE ? float_flag_invalid : 0) |
+                              (mxcsr & FPUS_DE ? float_flag_input_denormal_used : 0) |
                               (mxcsr & FPUS_ZE ? float_flag_divbyzero : 0) |
                               (mxcsr & FPUS_OE ? float_flag_overflow : 0) |
                               (mxcsr & FPUS_UE ? float_flag_underflow : 0) |
@@ -3267,14 +3268,8 @@  void update_mxcsr_status(CPUX86State *env)
 void update_mxcsr_from_sse_status(CPUX86State *env)
 {
     int flags = get_float_exception_flags(&env->sse_status);
-    /*
-     * The MXCSR denormal flag has opposite semantics to
-     * float_flag_input_denormal_flushed (the softfloat code sets that flag
-     * only when flushing input denormals to zero, but SSE sets it
-     * only when not flushing them to zero), so is not converted
-     * here.
-     */
     env->mxcsr |= ((flags & float_flag_invalid ? FPUS_IE : 0) |
+                   (flags & float_flag_input_denormal_used ? FPUS_DE : 0) |
                    (flags & float_flag_divbyzero ? FPUS_ZE : 0) |
                    (flags & float_flag_overflow ? FPUS_OE : 0) |
                    (flags & float_flag_underflow ? FPUS_UE : 0) |