Re: [PATCH] x86: use register variable to get stack pointer value

[Josh Poimboeuf]

On Fri, Sep 29, 2017 at 05:15:36PM +0300, Andrey Ryabinin wrote:
> Currently we use current_stack_pointer() function to get the value
> of the stack pointer register. Since commit f5caf621ee35
> ("x86/asm: Fix inline asm call constraints for Clang") we have stack
> register variable declared. It can be used instead of current_stack_pointer()
> function which allows to optimize away some excessive "mov %rsp, %<dst>"
> instructions:
> 
> -mov    %rsp,%rdx
> -sub    %rdx,%rax
> -cmp    $0x3fff,%rax
> -ja     ffffffff810722fd <ist_begin_non_atomic+0x2d>
> 
> +sub    %rsp,%rax
> +cmp    $0x3fff,%rax
> +ja     ffffffff810722fa <ist_begin_non_atomic+0x2a>
> 
> Remove current_stack_pointer(), rename __asm_call_sp to current_stack_pointer
> and use it instead of removed function.
> 
> Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>

Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>

-- 
Josh