Instead of #define TARGET_OS_USES_R18 which is not handled, pick R9 as an alternate static chain regnum and document that the port needs to be configured to issue -ffixed-r18 by default.
r9 is now available after the approval at https://gcc.gnu.org/pipermail/gcc-patches/2020-November/558094.html We have been using this variant with gcc-9 in-house for a while and I verified that I could get a build + reasonable test results with gcc-10. Olivier 2020-11-04 Olivier Hainque <hain...@adacore.com> gcc/ * config/aarch64-vxworks.h (TARGET_OS_USES_R18): Remove definition. (STATIC_CHAIN_REGNUM): Redefine to 9.
--- a/gcc/config/aarch64/aarch64-vxworks.h +++ b/gcc/config/aarch64/aarch64-vxworks.h @@ -60,12 +60,14 @@ along with GCC; see the file COPYING3. If not see #undef STACK_CHECK_PROTECT #define STACK_CHECK_PROTECT 16384 -/* The VxWorks environment on aarch64 is llvm-based only, uses R18 as - a TCB pointer. */ - +/* The VxWorks environment on aarch64 is llvm-based. */ #undef VXWORKS_PERSONALITY #define VXWORKS_PERSONALITY "llvm" -#undef TARGET_OS_USES_R18 -#define TARGET_OS_USES_R18 1 +/* VxWorks uses R18 as a TCB pointer. We must pick something else as + the static chain and R18 needs to be claimed "fixed". Until we + arrange to override the common parts of the port family to + acknowledge the latter, configure --with-specs="-ffixed-r18". */ +#undef STATIC_CHAIN_REGNUM +#define STATIC_CHAIN_REGNUM 9 -- 2.17.1
