help-smalltalk
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Help-smalltalk] About no_opt macro


From: Mathieu Suen
Subject: [Help-smalltalk] About no_opt macro
Date: Tue, 12 Oct 2010 14:28:18 +0100 (BST)

Hi,

Will reading the vm.def, I cam across the no_opt macro.
I guess is to avoid some optimization but but what kind of optimization and why.

The macro is define as: 

#define no_opt(x)    ({ __typeof__ ((x)) _result; \
             asm ("" : "=r" (_result) : "0" ((x))); _result; })


From what I understand is that it define a variable _result and force to move x 
into _result.

The macro is used in tha bytecode PLUS_SPECIAL an MINUS SPECIAL ... :

 intptr_t iresult = no_opt (iop1 + iop2);

Thanks for shading the light on this point.

-Mathk






reply via email to

[Prev in Thread] Current Thread [Next in Thread]