The patch is based on a reverted patch:
https://reviews.llvm.org/D103597. It was trying to rename registers
before alias check, which is not safe and causes miscompiles. This patch
does 2 things:
1. Do the renaming with necessary checks passed, including alias check.
2. Rename the register for the instructions between the pairs and
combine the second load into the first. By doing so we can just check
the renamability between the pairs and avoid scanning unknown amount of
instructions before/after the pairs.
Necessary refactoring has been made in order to reuse as much code
possible with STR renaming.
When an sreg sub-register of a q register was spilled,
AArch64InstrInfo::foldMemoryOperandImpl would emit a spill of a d
register, which gives the wrong result when the target is big-endian as
the following q register fill will put the value in the top half.
Fix this by greatly simplifying the existing code for widening the spill
to only handle wzr to xzr widening, as the default result we get if the
function returns nullptr is already that a widened spill will be
emitted.
PR #66334 tried to renumber slot indexes before register allocation, but
the numbering was still affected by list entries for instructions which
had been erased. Fix this to make the register allocator's live range
length heuristics even less dependent on the history of how instructions
have been added to and removed from SlotIndexes's maps.
This fills out some extra cases for sin/cos testing for various types under
Global ISel, which seem to all do OK. The existing tests in
sincospow-vector-expansion.ll can be removed, as they are now covered
elsewhere.
