Re: [PATCH v2 0/1] MR1065: ntdll: Add CFI unwind info to __wine_syscall_dispatcher (x86_64)

[Rémi Bernon (＠rbernon)]

Rémi Bernon (@rbernon) commented about dlls/ntdll/unix/signal_x86_64.c:
> -
>
> +#define __ASM_CFI_REG_IS_AT_OFFSET2_FROM_RCX(REG, OFFSET1, OFFSET2) \
> - __ASM_CFI_REG_IS_AT_OFFSET2_FROM_BREG(REG, __ASM_CFI_DW_OP_breg2, OFFSET1, OFFSET2)
> -
>
> +#define __ASM_CFI_REG_IS_AT_OFFSET1_FROM_RCX(REG, OFFSET) \
> - __ASM_CFI_REG_IS_AT_OFFSET1_FROM_BREG(REG, __ASM_CFI_DW_OP_breg2, OFFSET)
> -
>
> +#define __ASM_CFI_CFA_IS_AT_OFFSET_FROM_RBP(OFFSET) \
> - __ASM_CFI_CFA_IS_AT_OFFSET1_FROM_BREG(__ASM_CFI_DW_OP_breg6, OFFSET)
> -
>
> +#define __ASM_CFI_CFA_IS_AT_OFFSET_FROM_RSP(OFFSET) \
> - __ASM_CFI_CFA_IS_AT_OFFSET1_FROM_BREG(__ASM_CFI_DW_OP_breg7, OFFSET)
> -
>
> +#define __ASM_CFI_CFA_IS_AT_OFFSET_FROM_RCX(OFFSET1, OFFSET2) \
> - __ASM_CFI_CFA_IS_AT_OFFSET2_FROM_BREG(__ASM_CFI_DW_OP_breg2, OFFSET1, OFFSET2)
> -

What about something simpler like, 1) #define the `DW_` constants above in the file instead of the enums, and 2) re-use them here in the expressions, with something like:

```c
#define DW_OP_rcx DW_OP_breg2
#define DW_OP_rbp DW_OP_breg6
#define DW_OP_rsp DW_OP_breg7

#define DW_REG_rbx 0x03
#define DW_REG_rsi 0x04
#define DW_REG_rdi 0x05
#define DW_REG_rbp 0x06
#define DW_REG_rsp 0x07
#define DW_REG_r12 0x0c
#define DW_REG_r13 0x0d
#define DW_REG_r14 0x0e
#define DW_REG_r15 0x0f
#define DW_REG_rip 0x10

#define __ASM_CFI_STR(...) #__VA_ARGS__
#define __ASM_CFI_ESC(...)                        __ASM_CFI(".cfi_escape " __ASM_CFI_STR(__VA_ARGS__) "\n\t")
#define __ASM_CFI_CFA_IS_AT(base, lo, hi)         __ASM_CFI_ESC(DW_CFA_def_cfa_expression, 0x04, DW_OP_ ## base, lo, hi, DW_OP_deref)
#define __ASM_CFI_REG_IS_AT(reg, base, lo, hi)    __ASM_CFI_ESC(DW_CFA_expression, DW_REG_ ## reg, 0x03, DW_OP_ ## base, lo, hi)
```

And use that below as `__ASM_CFI_CFA_IS_AT(rcx,0x88,0x01)`, `__ASM_CFI_REG_IS_AT(rip,rcx,0xf0,0x00)`, etc...

I think using two bytes offsets everywhere simplifies the macros, although we'll need a bit more offset mangling by hand to encode them.