Patchwork [V4,05/22] softfloat: Fix float64_to_uint32_round_to_zero

login
register
mail settings
Submitter Tom Musta
Date Dec. 18, 2013, 8:19 p.m.
Message ID <1387397961-4894-6-git-send-email-tommusta@gmail.com>
Download mbox | patch
Permalink /patch/303066/
State New
Headers show

Comments

Tom Musta - Dec. 18, 2013, 8:19 p.m.
The float64_to_uint32_round_to_zero routine is incorrect.

For example, the following test pattern:

    425F81378DC0CD1F / 0x1.f81378dc0cd1fp+38

will erroneously set the inexact flag.

This patch re-implements the routine to use the float64_to_uint64_round_to_zero
routine.  If saturation occurs and the inexact flag was not previously set, it
will be cleared.

This contribution can be licensed under either the softfloat-2a or -2b
license.

V4: Correct commit commentary.  Corrected code to properly handle the
stickiness of the inexact flag.

Signed-off-by: Tom Musta <tommusta@gmail.com>
---
 fpu/softfloat.c |   15 +++++++--------
 1 files changed, 7 insertions(+), 8 deletions(-)
Peter Maydell - Dec. 19, 2013, 9:41 p.m.
On 18 December 2013 20:19, Tom Musta <tommusta@gmail.com> wrote:
> The float64_to_uint32_round_to_zero routine is incorrect.
>
> For example, the following test pattern:
>
>     425F81378DC0CD1F / 0x1.f81378dc0cd1fp+38
>
> will erroneously set the inexact flag.
>
> This patch re-implements the routine to use the float64_to_uint64_round_to_zero
> routine.  If saturation occurs and the inexact flag was not previously set, it
> will be cleared.

Code is OK but you forgot to update this commit message.

>
> This contribution can be licensed under either the softfloat-2a or -2b
> license.
>
> V4: Correct commit commentary.  Corrected code to properly handle the
> stickiness of the inexact flag.

These 'changes from previous version' comments should ideally go
below the "---" line, by the way. The idea is that the bit above the
line goes into the git commit history and should be a self-contained
description of the final patch.

> Signed-off-by: Tom Musta <tommusta@gmail.com>

If you fix the commit message you can add:
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM

Patch

diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index 6110e28..6112e2a 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -6595,19 +6595,18 @@  uint32 float64_to_uint32( float64 a STATUS_PARAM )
 
 uint32 float64_to_uint32_round_to_zero( float64 a STATUS_PARAM )
 {
-    int64_t v;
+    uint64_t v;
     uint32 res;
+    int old_exc_flags = get_float_exception_flags(status);
 
-    v = float64_to_int64_round_to_zero(a STATUS_VAR);
-    if (v < 0) {
-        res = 0;
-        float_raise( float_flag_invalid STATUS_VAR);
-    } else if (v > 0xffffffff) {
+    v = float64_to_uint64_round_to_zero(a STATUS_VAR);
+    if (v > 0xffffffff) {
         res = 0xffffffff;
-        float_raise( float_flag_invalid STATUS_VAR);
     } else {
-        res = v;
+        return v;
     }
+    set_float_exception_flags(old_exc_flags, status);
+    float_raise(float_flag_invalid STATUS_VAR);
     return res;
 }