When compiled with clang for arm64, some build errors were observed
along the fpu code. Moreover, data aborts were seen while running
the arm/fpu test due to misconfigured input/output args in the inline
assembly.

The series tries to addresses these issues.

- Raghavendra

Raghavendra Rao Ananta (3):
  arm: Fix clang error in sve_vl()
  arm: fpu: Convert 'q' registers to 'v' to satisfy clang
  arm: fpu: Fix the input/output args for inline asm in fpu.c

 arm/fpu.c                 | 46 +++++++++++++++++++--------------------
 lib/arm64/asm/processor.h |  2 +-
 2 files changed, 24 insertions(+), 24 deletions(-)


base-commit: f246b16099478a916eab37b9bd1eb07c743a67d5
-- 
2.47.0.105.g07ac214952-goog

On Tue, Oct 22, 2024 at 12:47:07AM +0000, Raghavendra Rao Ananta wrote:
> When compiled with clang for arm64, some build errors were observed
> along the fpu code. Moreover, data aborts were seen while running
> the arm/fpu test due to misconfigured input/output args in the inline
> assembly.
> 
> The series tries to addresses these issues.
> 
> - Raghavendra
> 
> Raghavendra Rao Ananta (3):
>   arm: Fix clang error in sve_vl()
>   arm: fpu: Convert 'q' registers to 'v' to satisfy clang
>   arm: fpu: Fix the input/output args for inline asm in fpu.c
> 
>  arm/fpu.c                 | 46 +++++++++++++++++++--------------------
>  lib/arm64/asm/processor.h |  2 +-
>  2 files changed, 24 insertions(+), 24 deletions(-)
> 
> 
> base-commit: f246b16099478a916eab37b9bd1eb07c743a67d5
> -- 
> 2.47.0.105.g07ac214952-goog
>

Hi Raghavendra,

With clang 18.1.8 (Fedora 18.1.8-1.fc40) I get a bunch of errors like
these

    arm/fpu.c:281:3: error: instruction requires: fp-armv8

I used my cross-clang series[1] and configured with

    ./configure --arch=arm64 --cc=clang --cflags='--target=aarch64' --cross-prefix=aarch64-linux-gnu-

[1] https://lore.kernel.org/all/20240911091406.134240-7-andrew.jones@linux.dev/

Thanks,
drew

Hi Andrew,

On Tue, Oct 22, 2024 at 6:10 AM Andrew Jones <andrew.jones@linux.dev> wrote:
>
> With clang 18.1.8 (Fedora 18.1.8-1.fc40) I get a bunch of errors like
> these
>
>     arm/fpu.c:281:3: error: instruction requires: fp-armv8
>
> I used my cross-clang series[1] and configured with
>
>     ./configure --arch=arm64 --cc=clang --cflags='--target=aarch64' --cross-prefix=aarch64-linux-gnu-
>
> [1] https://lore.kernel.org/all/20240911091406.134240-7-andrew.jones@linux.dev/
>
> Thanks,
> drew

I was able to reproduce the errors by pointing to a newer clang (20)
and applying your series.
I think we see the errors because llvm decided to disable loads and
stores on FP registers with "-mgeneral-regs-only" [1]. Explicitly
adding ".arch_extension fp" for the fp_reg_{read,write}() helped with
the build:

diff --git a/arm/fpu.c b/arm/fpu.c
index 6b0411d3..f44ed82a 100644
--- a/arm/fpu.c
+++ b/arm/fpu.c
@@ -38,7 +38,8 @@ static inline bool arch_collect_entropy(uint64_t *random)
 #define fpu_reg_read(val)                              \
 ({                                                     \
        uint64_t *__val = (val);                        \
-       asm volatile("stp q0, q1, [%0], #32\n\t"        \
+       asm volatile(".arch_extension fp\n"             \
+                    "stp q0, q1, [%0], #32\n\t"        \
                     "stp q2, q3, [%0], #32\n\t"        \
                     "stp q4, q5, [%0], #32\n\t"        \
                     "stp q6, q7, [%0], #32\n\t"        \
@@ -71,7 +72,8 @@ static inline bool arch_collect_entropy(uint64_t *random)
 #define fpu_reg_write(val)                             \
 do {                                                   \
        uint64_t *__val = (val);                        \
-       asm volatile("ldp q0, q1, [%0], #32\n\t"        \
+       asm volatile(".arch_extension fp\n"             \
+                    "ldp q0, q1, [%0], #32\n\t"        \
                     "ldp q2, q3, [%0], #32\n\t"        \
                     "ldp q4, q5, [%0], #32\n\t"        \
                     "ldp q6, q7, [%0], #32\n\t"        \

If you are fine with this, I can push it as a separate patch in v2.

Thank you.
Raghavendra

[1]: https://github.com/llvm/llvm-project/pull/77817