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Project submission for GCC 4.1 - AltiVec rewrite

I had already submitted this to Mark, but since I have improved a few rough spots in the code I think it's better to make it public.

* Project Title

AltiVec rewrite.

* Project Contributors

Paolo Bonzini

* Dependencies


> * Delivery Date

March 15th or earlier (the implementation is complete and has no regressions).

> * Description

The project reimplements the AltiVec vector primitives in a saner way,
without putting the burden on the preprocessor and instead processing
the "overloading" in the C front-end.

This would benefit compilation speed on AltiVec vector code, and move
the big table of AltiVec overloading pairs from an installed header
file to the compiler (an 11000-line header file is reduced to 500 lines
plus 2500 in the compiler).

The changes are so far self contained in the PowerPC backend, but I
would expect that a hack that I am using will require to be changed upon
review.  Unfortunately, a previous RFC I posted on the gcc mailing list
had (almost) no answer.

I plan to take a look at apple-ppc-branch, which supposedly does not need this hack, or to ask for feedback when I submit the project.

The current implementation improves the existing implementation in that
anything but predicates will accept unparenthesized literals even in C.
This line:

vec_add (x, (vector unsigned int) {1, 2, 3, 4})

now fails in C and works in C++, but with the new implementation would work in C as well. On the other hand, using a predicate like this

vec_all_eq (x, (vector unsigned int) {1, 2, 3, 4})

will still not work in C (it will *not* be a regression in C++, where it will be okay both without and with my changes). It would have to be written as

vec_all_eq (x, ((vector unsigned int) {1, 2, 3, 4}))

exactly as in the current implementation.


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