Functions like isMinGW() and isGnuLibC() have a good reason to exist: They look
at multiple components of the target. But functions like isWasm(), isDarwin(),
isGnu(), etc only exist to save 4-8 characters. I don't think this is a good
enough reason to keep them, especially given that:
* It's not immediately obvious to a reader whether target.isDarwin() means the
same thing as target.os.tag.isDarwin() precisely because isMinGW() and similar
functions *do* look at multiple components.
* It's not clear where we would draw the line. The logical conclusion before
this commit would be to also wrap Arch.isX86(), Os.Tag.isSolarish(),
Abi.isOpenHarmony(), etc... this obviously quickly gets out of hand.
* It's nice to just have a single correct way of doing something.
The old isARM() function was a portability trap. With the name it had, it seemed
like the obviously correct function to use, but it didn't include Thumb. In the
vast majority of cases where someone wants to ask "is the target Arm?", Thumb
*should* be included.
There are exactly 3 cases in the codebase where we do actually need to exclude
Thumb, although one of those is in Aro and mirrors a check in Clang that is
itself likely a bug. These rare cases can just add an extra isThumb() check.
The old vectorization helper (WipElementWise) was clunky and a bit
annoying to use, and it wasn't really flexible enough.
This introduces a new vectorization helper, which uses Temporary and
Operation types to deduce a Vectorization to perform the operation
in a reasonably efficient manner. It removes the outer loop
required by WipElementWise so that implementations of AIR instructions
are cleaner. This helps with sanity when we start to introduce support
for composite integers.
airShift, convertToDirect, convertToIndirect, and normalize are initially
implemented using this new method.
Most of this migration was performed automatically with `zig fmt`. There
were a few exceptions which I had to manually fix:
* `@alignCast` and `@addrSpaceCast` cannot be automatically rewritten
* `@truncate`'s fixup is incorrect for vectors
* Test cases are not formatted, and their error locations change
