The way that program sources were being constructed involved capturing
pointers to strings that were allocated on the stack, and then trying
to use them outside of that scope. This change uses a stringstream
defined in the outer scope to build the program instead.
The host compiler will not always calculate reference values
the same, depending on optimization level. It generates
instructions that do not respond to CPU rounding mode in
the same way. Use QCOM rounding mode emulation to correctly
calculate reference values on aarch64.
* 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>
