ahmed/OpenCL-CTS
1
0
Fork 0
mirror of https://github.com/KhronosGroup/OpenCL-CTS.git synced 2026-03-19 06:09:01 +00:00
Code Issues Packages Projects Releases Wiki Activity

Specify GCC flag -frounding-math on x86 (#873)

Browse Source 
* Specify GCC flag `-frounding-math` on x86

We have been seeing fails in `test_conversions` on x86_64 when converting to the following integer types from `cl_double` with a non-default rounding mode:

```
 char_rtn_double
 char_rtp_double
 int_rtn_double
 int_rtp_double
 long_rtn_double
 long_rtp_double
 long_sat_rtn_double
 long_sat_rtp_double
 short_rtn_double
 short_rtp_double
 uchar_rtp_double
 uint_rtp_double
 ulong_rtp_double
 ushort_rtp_double
```

After investigation it was discovered that `rint()` was incorrectly rounding `cl_double` inputs despite the rounding mode being correctly set using `fesetround()` beforehand. E.g  For 'char_rtn_double' `-3.5` was getting rounding to `-3.0` rather than `-4.0`.

This is a gcc issue https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92164 when using the builtin `rint()` implementation, rather than `std::rint()`, that only presents itself when compiling a Release build with `-O2` rather than Debug.

Adding the compiler flag `-fno-builtin-rint` to the CMake works around this problem, however based on the discussion in the gcc ticket using `-frounding-math` appears to be a more comprehensive fix. As `-frounding-math` tells gcc that the code will be modifying the rounding mode, removing the assumption that the same rounding mode is in effect everywhere.

* Set FENV_ACCESS ON in rounding_mode.h

Inform compilers which are aware of the `FENV_ACCESS` pragma that TUs
which include `harness/rounding_mode.h` may manipulate the floating
point environment.

* Remove FENV_ACCESS pragma from test_conversions.cpp

This pragma is now set in the included header
`test_common/harness/rounding_mode.h`

Co-authored-by: Kenneth Benzie (Benie) <k.benzie@codeplay.com>
This commit is contained in:
Ewan Crawford
2020-08-18 08:00:14 +01:00
committed by GitHub
parent ed50fcad2d
commit 5bb4d089dd
3 changed files with 4 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
test_conformance/conversions/test_conversions.cpp
View File

@@ -50,8 +50,6 @@
#include "Sleep.h"
#include "basic_test_conversions.h"
#pragma STDC FENV_ACCESS ON
#if (defined(_WIN32) && defined (_MSC_VER))
// need for _controlfp_s and rouinding modes in RoundingMode
#include "harness/testHarness.h"