|optimization and register allocation sastry@GODEL.MIEL.MOT.COM (1995-02-24)|
|Re: optimization and register allocation davidm@Rational.COM (1995-02-28)|
|Re: optimization and register allocation email@example.com (1995-03-04)|
|Re: optimization and register allocation firstname.lastname@example.org (1995-03-06)|
|From:||sastry@GODEL.MIEL.MOT.COM (Venkateshwara Sastry)|
|Date:||Fri, 24 Feb 1995 07:58:06 GMT|
Consider the following piece of code :
y = (-a) +f2 ;
... many uses of a here.
An optimizing compiler probably find that (-a) is loop invariant and
replace the code by
.... many uses of a here.
Now consider the case when GRA doesn't allocates register to t but
allocates a register to a. As a result code generator has to pick t
every time from memory which might be costiler than just negating a.
So we have essentially slowed down the genarated code. On the other
hand, had the GRA allocated a register to t it would have really
improved the generated code.
How can one determine whether to perform such optimizations( whose
behavior depend on register allocator) or not?
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