zlib-ng / zlib-ng / 27343456917 / 2

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Add branch prediction hints to deflate strategy hot loops

The deflate strategies were inconsistent about branch-prediction hints
on their per-iteration lookahead checks. deflate_quick marked both the
window-refill path unlikely and the steady-state path likely;
deflate_slow marked only the steady-state path; deflate_fast and
deflate_medium marked neither, leaving the compiler to guess the inner
loop's hot/cold block placement.

Mark the window-refill and end-of-input paths unlikely and the
steady-state path likely across deflate_fast, deflate_slow,
deflate_medium, deflate_rle, and deflate_huff, following deflate_quick,
so the rarely-taken refill block stays off the hot fall-through path
and block placement is consistent across all strategies.

2027 of 2150 branches covered (94.28%)

Branch coverage included in aggregate %.

8461 of 9549 relevant lines covered (88.61%)

20995391.71 hits per line