[Bug binutils/30099] objdump riscv: stop disassembling addi rd, rs, 0 with a relocation as mv rd, rs

[nelsonc1225 at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30099

--- Comment #2 from Nelson Chu <nelsonc1225 at sourceware dot org> ---
Some minor issues for implementation,

* I like the idea from Maciej to define a new instruction type, INSN_NORELOC,
in the opcode table.  But seems like we didn't left enough encodings for
INSN_TYPE, so the values of new types cannot be continuous with other old
types.  I just randomly choose 0x20000000 temporarily, maybe we should redefine
them to preserve enough encodings for future extend? or just extend them from
0x20000000 down?

* Not sure if it causes problems when we enable info->disassembler_needs_relocs
in the disassemble_init_for_target.  The INSN_HAS_RELOC needs
info->disassembler_needs_relocs be enabled.  But I only see arc enable it for
now, so not sure what the consequences are.


Otherwise, applying the proposed patch, I can get the expected result,

% cat tmp.s
foo:
addi    a0, a1, %lo(foo)
addi    a0, a1, 10
addi    a0, a1, 0
mv      a0, a1
% riscv64-unknown-elf-as tmp.s -o tmp.o
% riscv64-unknown-elf-objdump -d tmp.o 

tmp.o:     file format elf64-littleriscv


Disassembly of section .text:

0000000000000000 <foo>:
   0:   00058513                add     a0,a1,0
   4:   00a58513                add     a0,a1,10
   8:   00058513                mv      a0,a1
   c:   00058513                mv      a0,a1
% riscv64-unknown-elf-objdump -d -Mno-aliases tmp.o

tmp.o:     file format elf64-littleriscv


Disassembly of section .text:

0000000000000000 <foo>:
   0:   00058513                addi    a0,a1,0
   4:   00a58513                addi    a0,a1,10
   8:   00058513                addi    a0,a1,0
   c:   00058513                addi    a0,a1,0

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