Re: [Lightning] How to call varargs functions from lightning in x86_64?

[Paulo César Pereira de Andrade]

  Hi,

  The attached patch pass these tests in my testing tool:

http://code.google.com/p/exl/source/browse/trunk/check/lightning/varargs.tst

the test basically does:
1.
  o call sprintf with 10 integer arguments
  o call sscanf with 10 integer pointer arguments
  o check that sscanf reads back what sprintf wrote
2.
  o call sprintf with 10 double arguments
  o call sscanf with 10 double pointer arguments
  o check that sscanf reads back what sprintf wrote
3.
  o call a jit function with 10 integer arguments
  o the jit function validates the 10 integer arguments
4.
  o call a jit function with 10 double arguments
  o the jit function validates the 10 double arguments
5.
  o call a jit function with mixed long,double,long,double...
    totalling 10 longs and 10 doubles
  o the jit function validates the arguments
6.
  o call sprintf with 10 times the pattern of "%d %f", and pass
    10 pairs of longs and doubles
  o call sscanf and validate the buffer contents

  This works in x86_64, but did not check on i386 yet.
Very experimental patch, and probably will only work with varargs
functions for > 8 double arguments, as described in the commit message.
Still need to check calls to prototyped functions with more than 8
double arguments, and, if that changes, that it would be required to
have some hint to jit_prepare, what would not be a bad idea at all,
as then, it could avoid setting %al for the varargs abi, what it
does regardless of calling a varargs or not (but that is minimal
overhead)...

  Please review/comment.

  This has the tricks that should be common to other lightning logic:
o must call arg_* for every arguments, in left to right order
o must call  getarg_* for every argument, in left to right order
o must call jit_prepare before jit_prepare_{f,d} and then may call
  jit_prepare_{f,d} any times, but before pushing arguments
If not doing the above, it will not work correctly if generating
more then one jit function, or nested jit functions.

Thanks,
Paulo

0001-Experimental-x86_64-support-for-any-number-of-intege.patch
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