Re: [ros-dev] [ros-diffs] [ion] 52807: [KERNEL32]: Optimize SwitchToFiber to simply use "ret" to jump between fibers, instead of saving EIP and doing a JMP. Bug #50: SwitchToFiber needs to check if FXSR is *NOT* present in ...

[Timo Kreuzer]

This won't work, since new Fibers, created with CreateFiber(Ex) don't 
push a "return address" on the stack, but set the Eip member to 
BaseFiberStartup.

Am 23.07.2011 14:08, schrieb [e-mail]:
> Author: ion
> Date: Sat Jul 23 12:08:36 2011
> New Revision: 52807
>
> URL: http://svn.reactos.org/svn/reactos?rev=52807&view=rev
> Log:
> [KERNEL32]: Optimize SwitchToFiber to simply use "ret" to jump between fibers, instead of saving EIP and doing a JMP.
> Bug #50: SwitchToFiber needs to check if FXSR is *NOT* present in order to skip using ldmxcsr/stmxcsr. Previously, it would check if it's unsupported, and jump past the instruction if it was (resulting in invalid opcode instructions on older systems)
> 50 bugs. Penance has been paid.
>
> Modified:
>      trunk/reactos/dll/win32/kernel32/client/i386/fiber.S
>
> Modified: trunk/reactos/dll/win32/kernel32/client/i386/fiber.S
> URL: http://svn.reactos.org/svn/reactos/trunk/reactos/dll/win32/kernel32/client/i...
> ==============================================================================
> --- trunk/reactos/dll/win32/kernel32/client/i386/fiber.S [iso-8859-1] (original)
> +++ trunk/reactos/dll/win32/kernel32/client/i386/fiber.S [iso-8859-1] Sat Jul 23 12:08:36 2011
> @@ -26,20 +26,16 @@
>       mov [eax+FIBER_CONTEXT_EDI], edi
>       mov [eax+FIBER_CONTEXT_EBP], ebp
>
> /* Save the return address */
>
> mov ebx, [esp]
>
> mov [eax+FIBER_CONTEXT_EIP], ebx
> /* Check if we're to save FPU State */
> cmp dword ptr [eax+FIBER_CONTEXT_FLAGS], CONTEXT_FULL OR CONTEXT_FLOATING_POINT
> jnz NoFpuStateSave
>
> /* Save the FPU State (Status and Control)*/
> fstsw [eax+FIBER_CONTEXT_FLOAT_SAVE_STATUS_WORD]
>
> fstcw [eax+FIBER_CONTEXT_FLOAT_SAVE_CONTROL_WORD]
>
> fnstcw [eax+FIBER_CONTEXT_FLOAT_SAVE_CONTROL_WORD]
>
> /* Check if the CPU supports SIMD MXCSR State Save */
> cmp byte ptr ds:[PROCESSOR_FEATURE_FXSR], 0
> cmp byte ptr ds:[PROCESSOR_FEATURE_FXSR], 1
>  jnz NoFpuStateSave
>  stmxcsr [eax+FIBER_CONTEXT_DR6]
>
> @@ -103,7 +99,7 @@
>   ControlWordEqual:
>   /* Load the new one */
> cmp byte ptr ds:[PROCESSOR_FEATURE_FXSR], 0
> cmp byte ptr ds:[PROCESSOR_FEATURE_FXSR], 1
>  jnz NoFpuStateRestore
>  ldmxcsr [ecx+FIBER_CONTEXT_DR6]
>
> @@ -121,7 +117,8 @@
>       mov [edx+TEB_FLS_DATA], eax
>   /* Jump to new fiber */
> jmp dword ptr [ecx+FIBER_CONTEXT_EIP]
> mov esp, [ecx+FIBER_CONTEXT_ESP]
> ret 4
>
> +END
>
> -END
>   /* EOF */