Re: Global versus Stack variables

henry@spsystems.net (Henry Spencer)
21 Nov 2005 22:43:24 -0500

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From: henry@spsystems.net (Henry Spencer)
Newsgroups: comp.compilers
Date: 21 Nov 2005 22:43:24 -0500
Organization: SP Systems, Toronto, Canada
References: 05-11-094
Keywords: design, optimize, storage
Posted-Date: 21 Nov 2005 22:43:24 EST

shrey <shreyas76@gmail.com> wrote:
>...What is the impact of a variable being a global or a local
>variable on optimizations. In other words, is it likelier to produce
>better code if a variable is local than global...


Broadly speaking, the more the compiler knows about how and where a
variable is used, the better the code it can produce. Particularly in
compiler systems that support separate compilation, it's often very
difficult to do any real optimization involving global variables, because
when compiling any particular module/procedure/etc., the compiler doesn't
know the whole story of how the variable is used. It's usually much
easier for a compiler to know everything about a local variable.
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