On Thu, Apr 11, 2024 at 09:11:13PM -0700, Charlie Jenkins wrote:
When alternatives are disabled, riscv_cpu_isa_extension_(un)likely() checks if the current cpu supports the selected extension if not all cpus support the extension. It is sufficient to only check if the current cpu supports the extension.
The alternatives code to handle if all cpus support an extension is factored out into a new function to support this.
Signed-off-by: Charlie Jenkins charlie@rivosinc.com
static __always_inline bool riscv_cpu_has_extension_unlikely(int cpu, const unsigned long ext) {
- if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) && riscv_has_extension_unlikely(ext))
return true;
- compiletime_assert(ext < RISCV_ISA_EXT_MAX,
"ext must be < RISCV_ISA_EXT_MAX");
- return __riscv_isa_extension_available(hart_isa[cpu].isa, ext);
- if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) && __riscv_has_extension_unlikely_alternatives(ext))
return true;- else
return __riscv_isa_extension_available(hart_isa[cpu].isa, ext);}
static __always_inline bool riscv_cpu_has_extension_likely(int cpu, const unsigned long ext) { if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) && riscv_has_extension_likely(ext)) return true;
return __riscv_isa_extension_available(hart_isa[cpu].isa, ext); }
This is the code as things stand. If alternatives are disabled, the if statement becomes if (0 && foo) which will lead to the function call getting constant folded away and all you end up with is the call to __riscv_isa_extension_available(). Unless I am missing something, I don't think this patch has any affect?
Thanks, Conor.