diff options
| author | andromeda <andromeda@lenovo> | 2026-03-11 20:14:13 +0100 |
|---|---|---|
| committer | andromeda <andromeda@lenovo> | 2026-03-11 20:14:13 +0100 |
| commit | a84f2d7453e6695a677045a479667c3881d773f3 (patch) | |
| tree | 9d0077a7aa2794ff871fa27aa5bc3192fa00ea19 | |
| parent | e6d7cb2f2104183e6d090ead5ad0f491f603e3ce (diff) | |
add get_ModRM
| -rw-r--r-- | twasm/asm/main.asm | 31 |
1 files changed, 27 insertions, 4 deletions
diff --git a/twasm/asm/main.asm b/twasm/asm/main.asm index 96d15bc..c8dd826 100644 --- a/twasm/asm/main.asm +++ b/twasm/asm/main.asm @@ -320,6 +320,29 @@ get_tte_typed_metadata: ; ------------------------------------------------------------------------------ get_direct_addressing_ModRM: + mov dl, 11b + call get_ModRM + ret + +; ------------------------------------------------------------------------------ +; get_ModRM +; +; description: +; given 2 register tokens and the mod bits, returns the ModR/M byte +; +; parameters: +; di = token table entry `reg` +; si = token table entry `R/M` +; dl = lower 2 bits: mod bits. The rest is ignored +; +; returned: +; al = ModR/M byte; the rest of rax is zeroed +; ------------------------------------------------------------------------------ + +get_ModRM: + and dl, 11b ; mask for mod bits + shl dl, 6 + ; di = tte call get_reg_bits ; al = reg bits @@ -332,12 +355,12 @@ get_direct_addressing_ModRM: call get_reg_bits ; al = reg bits - mov dl, al + mov cl, al xor eax, eax - or al, 11b << 6 ; mod bits - or al, bl ; reg bits - or al, dl ; R/M bits + or al, dl ; mod bits + or al, bl ; reg bits + or al, cl ; R/M bits and rax, 0xFF ; mask for byte ret |