Re: recommended alignment for local i386 FP variables patch (version 2)

[John Wehle <john at feith dot com>]

>>   3) It may be desirable to use DATA_ALIGNMENT instead of defining a
>>      new macro (LOCAL_ALIGNMENT).  I defined a new macro so I could
>>      use it to control the changes I made (in a separate patch) to reload.
> Maybe, maybe not.  Wasted space on the stack is generally more important
> than wasted space in the static store.  We may (or may not) want throttle
> alignment of stack items to 64bits, with the exception of XFmode items which
> we'd want to align to 128bits.  Opinions on this would be greatly appreciated.

I was leaning towards only giving extra alignment to DFmode and XFmode items
which is why the definition I supplied for LOCAL_ALIGNMENT doesn't handle
the additional cases that I have in DATA_ALIGNMENT.  If nothing else, it's
probably a reasonable starting point which can be adjusted later.

> In your change to stmt.c, you're caling assign_temp and claiming that the
> result must be addressable.  It might be best to only make it addressable if
> absolutely necessary.  Addressable stack slots can inhibit some optimizations.

I believe that this (requiring addressable) is what's intended by expand_decl
at that point.  The general case of non-BLKmode variables is handled earlier
in expand_decl.

-- John
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