[PATCH bpf] libbpf: Handle GCC built-in types for Arm NEON
Daniel Borkmann
daniel at iogearbox.net
Tue Aug 11 10:10:31 EDT 2020
On 8/10/20 2:28 PM, Jean-Philippe Brucker wrote:
> When building Arm NEON (SIMD) code, GCC emits built-in types __PolyXX_t,
> which are not recognized by Clang. This causes build failures when
> including vmlinux.h generated from a kernel built with CONFIG_RAID6_PQ=y
> and CONFIG_KERNEL_MODE_NEON. Emit typedefs for these built-in types,
> based on the Clang definitions. poly64_t is unsigned long because it's
> only defined for 64-bit Arm.
>
> Including linux/kernel.h to use ARRAY_SIZE() incidentally redefined
> max(), causing a build bug due to different types, hence the seemingly
> unrelated change.
>
> Reported-by: Jakov Petrina <jakov.petrina at sartura.hr>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org>
Looks like this was fixed here [0], but not available on older clang/LLVM
versions, right?
[0] https://reviews.llvm.org/D79711
[...]
>
> +static const char *builtin_types[][2] = {
> + /*
> + * GCC emits typedefs to its internal __PolyXX_t types when compiling
> + * Arm SIMD intrinsics. Alias them to the same standard types as Clang.
> + */
> + { "__Poly8_t", "unsigned char" },
> + { "__Poly16_t", "unsigned short" },
> + { "__Poly64_t", "unsigned long" },
> + { "__Poly128_t", "unsigned __int128" },
In that above LLVM link [0], they typefdef this to signed types ... which one
is correct now?
// For now, signedness of polynomial types depends on target
OS << "#ifdef __aarch64__\n";
OS << "typedef uint8_t poly8_t;\n";
OS << "typedef uint16_t poly16_t;\n";
OS << "typedef uint64_t poly64_t;\n";
OS << "typedef __uint128_t poly128_t;\n";
OS << "#else\n";
OS << "typedef int8_t poly8_t;\n";
OS << "typedef int16_t poly16_t;\n";
OS << "typedef int64_t poly64_t;\n";
OS << "#endif\n";
> +};
> +
> +static void btf_dump_emit_int_def(struct btf_dump *d, __u32 id,
> + const struct btf_type *t)
> +{
> + const char *name = btf_dump_type_name(d, id);
> + int i;
> +
> + for (i = 0; i < ARRAY_SIZE(builtin_types); i++) {
> + if (strcmp(name, builtin_types[i][0]) == 0) {
> + btf_dump_printf(d, "typedef %s %s;\n\n",
> + builtin_types[i][1], name);
> + break;
> + }
> + }
> +}
> +
> static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
> const struct btf_type *t)
> {
>
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