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78a07aa90b
NIR shifts are defined to truncate the shift amount to the number of bits
needed to represent the bit-size of the value shifted. LLVM treats large
shifts as poison. This fix achieves NIR semantics for shifts.
As an example, a|(b << 32), where "a" is 32bits, should produce a|b
according to NIR (because 32&31 == 0).
This caused LLVM to incorrectly optimize "(a >> c) | (b << (32 - c))" to a
u2u32(pack_64_2x32(a, b) >> c) (v_alignbit_b32), when the original NIR
should have returned "a | b" if c==0.
Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Mihai Preda <mhpreda@gmail.com>
Reviewed-by: Qiang Yu <yuq825@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Cc: mesa-stable
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19966>
(cherry picked from commit
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