Intravision/reactos
1
0
Fork 0
mirror of https://github.com/reactos/reactos.git synced 2024-10-01 06:57:08 +00:00
Code Issues Packages Projects Releases Wiki Activity

[KERNEL32]: Optimize SwitchToFiber to simply use "ret" to jump between fibers, instead of saving EIP and doing a JMP.

Browse source 
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.

svn path=/trunk/; revision=52807
This commit is contained in:
Alex Ionescu 2011-07-23 12:08:36 +00:00
parent 8a06cf76c6
commit 7eda2f21b7
1 changed files with 6 additions and 9 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

15
reactos/dll/win32/kernel32/client/i386/fiber.S
View file

@ -26,20 +26,16 @@ _SwitchToFiber@4:
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 @@ StatusWordChanged:
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 @@ NoFpuStateRestore:
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
/* EOF */