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From: worley@compass.com (Dale Worley)
Newsgroups: comp.compilers
Subject: Register allocation in the presence of pointers
Message-ID: <1990Feb22.180326.11309@esegue.segue.boston.ma.us>
Date: 22 Feb 90 18:03:26 GMT
Sender: compilers-sender@esegue.segue.boston.ma.us
Reply-To: worley@compass.com (Dale Worley)
Organization: Compilers Central
Lines: 19
Approved: compilers@esegue.segue.boston.ma.us

Mohd Hanafiah b. Abdullah writes:
> How does one perform register allocation on scalar variables that may
> be pointed to by others?

The usual strategy is to never leave the value of the variable in a register,
since it may be fetched or modified at any time via the pointer.  On some
hardware, registers have addresses and this conservative strategy may not be
needed.  A more interesting approach would be to analyze which parts of the
program might reference the variable through a pointer and which can not --
then you know in which parts of the program you have to leave the value in its
"official" location and in which parts you can leave the variable in a
register.  This requires serious global data-flow analysis, which, although
possible, is rarely implemented.

Dale Worley		Compass, Inc.			worley@compass.com
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