Comment 18 for bug 1953128

It's been this way now for over 20 years. A single instruction cannot take a constant and a memory for the same operand, so this has been used in the backend to trigger the minipool generation: a constant in an operand that takes a memory triggers a minipool spill to be pushed.

If we changed this now we risk breaking existing inline asms that exploit this feature (good or bad) and expect a constant to be pushed into a minipool entry.