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Re: [Help-gsl] Uninitialized variables and signaling NaNs

From: Andrew W. Steiner
Subject: Re: [Help-gsl] Uninitialized variables and signaling NaNs
Date: Sun, 8 Aug 2010 16:04:41 -0400


     Thanks for your thoughts. My naive guess is
that It would be difficult, if not impossible for the
optimizer to know this, as one could always
insert a call to an external function which
ostensibly initializes the variable but may or
may not fail to do so. Additionally, I
don't forsee any work on the C/C++ compilers
which guarantees that the optimizer will
accomplish this task, leaving it up to those
who write the source code to take care of it.

Take care,

On Sun, Aug 8, 2010 at 3:28 PM, Jochen Küpper
<address@hidden> wrote:
> Isn't that an issue that should be handled by the optimizer? That's the
> instance that knows whether this issue might occur or not, i.e., it
> knows whether the variable is put into a register or not.
> Therefore, the optimizer should initialize this variable if it's put into a
> register (probably using a switch to turn off or on). Obviously, it then
> has to determine whether it is still worth the register usage with
> the added overhead of initialization.
> Or would it actually be feasible to use the register (for x) without
> moving the content of &x but instead using whatever happens to
> be in the register?

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