ir3: emit uniform iadd3 as two adds
The sad instruction (used for iadd3) doesn't support the scalar ALU. This means we might fall back to non-earlypreamble whenever we use it in the preamble. Prevent this by emitting it as two adds instead.
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The sad instruction (used for iadd3) doesn't support the scalar ALU. This means we might fall back to non-earlypreamble whenever we use it in the preamble. Prevent this by emitting it as two adds instead.