Enhance assembler/disassembler output for lui/c.lui about riscv-binutils-gdb HOT 4 CLOSED

lui takes the immediate right-shifted by 12 and unsigned (i.e. 0x0 - 0xfffff), so -4096 would be 0xfffff. I fear that changing this will cause problems. In your proposal, what range of inputs would lui accept?

Seems better to rely on li if you want to use constants like -4096; this is what GCC does.

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Humm, I expect it lui can accept two kind of input, shifted immediate and signed integer.
For shifted immediate, accept 0xfffff000 instead of 0xfffff and output 0xfffff000 in disassembler.
For signed integer, accept all encode-able number.

And for disassembler, naybe we can add both kind of output?

0000000000000000 <x>:
   0:	fffffab7          	lui	s5,0xfffff000 # -4096

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If we changed it to accept 0xfffff000 instead of 0xfffff, this would make sense, but I really don't want to make a backwards-incompatible change like this. It won't break gcc, but it will break hand-written assembly.

I think in the assembler style guide, we just tell people to use li, not lui. We can make it a requirement that li uses lui if the result is in lui range, so that it is predictable.

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OK, I agree it's will break backwards-compatible, and the let the disassembler output keep the same to prevent inconsistent or any confuse.

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