[AArch64][SVE2p1] Allow more uses of mask in performActiveLaneMaskCombine (#159360)

The combine replaces a get_active_lane_mask used by two extract
subvectors with a single paired whilelo intrinsic. When the instruction
is used for control flow in a vector loop, an additional extract of element
0 may introduce other uses of the intrinsic such as ptest and reinterpret
cast, which is currently not supported.

This patch changes performActiveLaneMaskCombine to count the number
of extract subvectors using the mask instead of the total number of uses,
and returns the concatenated results of get_active_lane_mask.

0 files changed, 0 insertions, 0 deletions