Hi Andrew, On Tue, Oct 22, 2024 at 6:10 AM Andrew Jones <andrew.jones@xxxxxxxxx> 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@xxxxxxxxx/ > > 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
