diff options
author | Palmer Dabbelt <palmerdabbelt@google.com> | 2020-02-27 11:07:28 -0800 |
---|---|---|
committer | Palmer Dabbelt <palmerdabbelt@google.com> | 2020-03-03 10:28:13 -0800 |
commit | 52e7c52d2ded5908e6a4f8a7248e5fa6e0d6809a (patch) | |
tree | 43ea26b8f12ba519ea77b8c83fb9cdefb46e7430 /arch/riscv/include | |
parent | 064223b947a8c3d0b35a4ac9ae6e31e3f77657fd (diff) |
RISC-V: Stop relying on GCC's register allocator's hueristics
GCC allows users to hint to the register allocation that a variable should be
placed in a register by using a syntax along the lines of
function(...) {
register long in_REG __asm__("REG");
}
We've abused this a bit throughout the RISC-V port to access fixed registers
directly as C variables. In practice it's never going to blow up because GCC
isn't going to allocate these registers, but it's not a well defined syntax so
we really shouldn't be relying upon this. Luckily there is a very similar but
well defined syntax that allows us to still access these registers directly as
C variables, which is to simply declare the register variables globally. For
fixed variables this doesn't change the ABI.
LLVM disallows this ambiguous syntax, so this isn't just strictly a formatting
change.
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Diffstat (limited to 'arch/riscv/include')
-rw-r--r-- | arch/riscv/include/asm/current.h | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/riscv/include/asm/current.h b/arch/riscv/include/asm/current.h index dd973efe5d7c..1de233d8e8de 100644 --- a/arch/riscv/include/asm/current.h +++ b/arch/riscv/include/asm/current.h @@ -17,6 +17,8 @@ struct task_struct; +register struct task_struct *riscv_current_is_tp __asm__("tp"); + /* * This only works because "struct thread_info" is at offset 0 from "struct * task_struct". This constraint seems to be necessary on other architectures @@ -26,8 +28,7 @@ struct task_struct; */ static __always_inline struct task_struct *get_current(void) { - register struct task_struct *tp __asm__("tp"); - return tp; + return riscv_current_is_tp; } #define current get_current() |