[Info-vax] Hard links on VMS ODS5 disks

[Dan Cross]

In article <45fd1f30-55fb-4691-a561-e5941143a6fcn at googlegroups.com>,
John Reagan  <xyzzy1959 at gmail.com> wrote:
>[big snip]
>Macro doesn't use the LLVM optimizer (it doesn't use the GEM one either).  All the
>branching between routines doesn't fit the high-level model.
>
>Macro does a limited job of pulling address computations out of loops if there are
>free registers (and on x86, the answer is "almost never").  
>
>With GEM, AMACRO/IMACRO gets the benefit of GEM's instruction level peephole
>optimizer.  That doesn't exist in that form for LLVM.  So XMACRO today has several
>"branches to branches" and is sloppy with x86 condition codes.  However, we think
>the microarchitecture and predictive execution takes care of those branches to branches
>and the like.
>
>In general Macro-32 code is optimized by the human while typing it in.

This begs a question: how useful are those optimizations?  I
imagine many are based on an execution environment that is not
the actual target anymore; is it possible that something that
was a clear win on VAX is a pessimization as implemented on
x86?

	- Dan C.