Basecase assembly optimisation project

[Niels Möller]

Torbjorn Granlund <tg at gmplib.org> writes:

> We don't handle alternatives currently, except with a loop around the
> loopmixer.  One could think of several classes, some known to the tool,
> others not-always-valid only by source file annotation.  Examples of the
> former would be "xor rax,rax" vs "xor eax,eax" and "mov reg,reg" vs lea
> (reg),reg.

Another feature, which I looked into while ago without getting very far
with the loopmixer, is to make it understand associativity. I.e, try
reordering certain instructions with the same destination register, like

  xor	%r8, %rax
  xor	%r9, %rax

or

  add	%r8, %rax
  add	%r9, %rax
  
This is possible if nothing else depends on the intermediate results
(including no dependencies on status flags).

Probably more useful for cryptographic loops than for arithmetic.

Regards,
/Niels

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