[ARM] compute cf for shift/rotate

[W0ni]

This partially addresses #1456

• Moves rrx computation inside the functions, this allows to do the carry flag computation related to RRX
• Adds a shifter/rotate template for the carry flag similar to the one in x86

It is still (at least) left to:

• compute the carry flag of some instructions with immediates.
  Here is an example A32ExpandImm_C (https://developer.arm.com/documentation/ddi0597/2023-06/Shared-Pseudocode/aarch32-functions-common?lang=en#impl-aarch32.A32ExpandImm_C.2). Used by ANDS, BICS, EORS, MOVS, MVNS, ORRS, TEQ, TST with immediates.
  The equation is something like cf= ROR(zExt32(imm[0:8], imm[8:12] << 1).MSB() (if 2*imm[8:12] != 0). This is tricky because the semantics don't know the rotate amount that was used. Maybe the additional_info object on instructions could store useful data like rotate amount and maybe the encoding category (A1, A2, T1, T2...)?

• Update the semantic tests to include the carry flag.

Related additional work:

• Maybe we could also clean up a bit the code (use flag functions more often, replace isinstance for Expr* by is_XXX...)
• Maybe handle the exception when setflags AND dst=PC?

[serpilliere]

Hi @W0ni,
Thanks for the PR: We will look into it soon!
(nice tipo catch on the "compote".)

[W0ni]

Hello @serpilliere ,
While adding the tests for MOVS, I noticed a bug in the disassembly of the shifters. I fixed it in the commit 71e4e09 along with the related tests. (See DecodeImmShift at https://developer.arm.com/documentation/ddi0597/2023-06/Shared-Pseudocode/aarch32-functions-common?lang=en#impl-aarch32.DecodeImmShift.2 for reference)
I also added the tests for the MOVS instuctions in 1885f3c.

[serpilliere]

Hi @W0ni !

I was looking at your patch regarding the disassembling fix, more precisely the support of ASR/LSR and RRX during instruction decoding. I think we should add a regression test on the disassemble engine itself (test/arm/arch.py), in order to test the freshly added code.

Do you want to add it to the PR, or do you prefer I add it?
(I was thinking of an asm/disasm of the fixed versions)