[Bug target/79905] ICE in canonical types differ for identical types __vector(4) int and V4i {aka __vector(4) int}

[meissner at linux dot vnet.ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79905

--- Comment #6 from Michael Meissner <meissner at linux dot vnet.ibm.com> ---
On Thu, Mar 16, 2017 at 03:10:19PM +0000, rguenth at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79905

Generally, the "vector" keyword is a conditional macro that looks at the next
token or two to decide whether or not to expand the macro.  If the next token
is one of the standard types or __bool/__pixel, then __vector/vector is
expanded to:

        __attribute__((altivec(vector__))

The magic is in rs6000-c.c, particularly in altivec_categorize_keyword,
init_vector_keywords, rs6000_macro_to_expand, and rs6000_cpu_cpp_builtins.