This is based on ideas from @nafi to:
- use a branchless version of 'cmp' for 'uint32_t',
- completely resolve the lexicographic comparison through vector
operations when wide types are available. We also get rid of byte
reloads and serializing '__builtin_ctzll'.
I did not include the suggestion to replace comparisons of 'uint16_t'
with two 'uint8_t' as it did not seem to help the codegen. This can
be revisited in sub-sequent patches.
The code been rewritten to reduce nested function calls, making the
job of the inliner easier and preventing harmful code duplication.
Reviewed By: nafi3000
Differential Revision: https://reviews.llvm.org/D148717
bd4f978754