This patch teaches the AsmParser to accept add/adds/sub/subs/cmp/cmn
with a negative immediate operand and convert them as shown:
add Rd, Rn, -imm -> sub Rd, Rn, imm
sub Rd, Rn, -imm -> add Rd, Rn, imm
adds Rd, Rn, -imm -> subs Rd, Rn, imm
subs Rd, Rn, -imm -> adds Rd, Rn, imm
cmp Rn, -imm -> cmn Rn, imm
cmn Rn, -imm -> cmp Rn, imm
Those instructions are an alternate syntax available to assembly coders,
and are needed in order to support code already compiling with some other
assemblers (gas). They are documented in the "ARMv8 Instruction Set
Overview", in the "Arithmetic (immediate)" section. This makes llvm-mc
a programmer-friendly assembler !
This also fixes PR20978: "Assembly handling of adding negative numbers
not as smart as gas".
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241166 91177308-0d34-0410-b5e6-96231b3b80d8
