* Project Title
AltiVec rewrite.
* Project Contributors
Paolo Bonzini
* Dependencies
none
> * 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.
Paolo
