Handle up to 2^16 - 1 operands per inst, and error properly on more. #226
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This PR addresses an underlying limitation that became a problem for Cranelift recently, after folding return-value loads into call pseudoinsts (thus producing single instructions with many operands): we only supported 255 operands per instruction. It appears that `Use` was using a `u8` for the "slot index" for an operand as a result of earlier optimization/packing efforts. However, the current shape of the struct leaves a padding byte free, so we should be able to expand to a `u16` with no loss in performance. Furthermore, previously we weren't catching the overflow, but rather were silently wrapping around (eek). This properly returns a `RegAllocError::TooManyOperands` now if an instruction has too many operands (more than `u16::MAX`).
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Includes fix from bytecodealliance#226 for instructions with more than `u8::MAX` operands.
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Includes fix from #226 for instructions with more than `u8::MAX` operands.
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This PR addresses an underlying limitation that became a problem for Cranelift recently, after folding return-value loads into call pseudoinsts (thus producing single instructions with many operands): we only supported 255 operands per instruction.
It appears that
Usewas using au8for the "slot index" for an operand as a result of earlier optimization/packing efforts. However, the current shape of the struct leaves a padding byte free, so we should be able to expand to au16with no loss in performance.Furthermore, previously we weren't catching the overflow, but rather were silently wrapping around (eek). This properly returns a
RegAllocError::TooManyOperandsnow if an instruction has too many operands (more thanu16::MAX).