On 20/11/2023 10:41, Christophe Lyon wrote:
Hi Richard,
On Mon, 13 Nov 2023 at 15:27, Richard Earnshaw <rearn...@arm.com> wrote:
Add an arm-specific test to check_effective_target_hard_float for
Arm to handle cases where we only have single-precision FP in hardware.
gcc/testsuite:
* lib/target-supports.exp (check_effective_target_hard_float): Add
arm-specific test.
---
gcc/testsuite/lib/target-supports.exp | 11 +++++++++++
1 file changed, 11 insertions(+)
Our CI has detected a problem when testing this patch for cortex-m33:
with
-mthumb/-march=armv8-m.main+dsp+fp/-mtune=cortex-m33/-mfloat-abi=hard/-mfpu=auto
and GCC configured with --disable-multilib --with-mode=thumb
--with-cpu=cortex-m33 --with-float=hard
FAIL:
gcc:gcc.dg/torture/dg-torture.exp=gcc.dg/torture/fp-double-convert-float-1.c
-O0 execution test
FAIL:
gcc:gcc.dg/torture/dg-torture.exp=gcc.dg/torture/fp-double-convert-float-1.c
-O1 execution test
FAIL:
gcc:gcc.dg/torture/dg-torture.exp=gcc.dg/torture/fp-double-convert-float-1.c
-O2 execution test
FAIL:
gcc:gcc.dg/torture/dg-torture.exp=gcc.dg/torture/fp-double-convert-float-1.c
-O2 -flto -fno-use-linker-plugin -flto-partition=none execution
test
FAIL:
gcc:gcc.dg/torture/dg-torture.exp=gcc.dg/torture/fp-double-convert-float-1.c
-O2 -flto -fuse-linker-plugin -fno-fat-lto-objects execution test
FAIL:
gcc:gcc.dg/torture/dg-torture.exp=gcc.dg/torture/fp-double-convert-float-1.c
-O3 -g execution test
FAIL:
gcc:gcc.dg/torture/dg-torture.exp=gcc.dg/torture/fp-double-convert-float-1.c
-Os execution test
I think this technically is a real bug in the port. This test changes
the rounding modes, but cortex-m33 only has a single-precision FP unit,
so single-precision is handled in HW, while double-precision is handled
in SW. The soft-float functions don't support changing the rounding
mode, and certainly not through fesetround(), so we don't get the
expected results. I think the test would always have failed, but we
didn't run it in the past as the default test for HW fp only checked for
double precision HW.
Fixing the real problem is not trivial though, especially in a mixed
hard/soft environment.
We use qemu for testing. Do these tests pass in your configuration?
Thanks,
Christophe
R.
