X-Git-Url: https://git.rrq.au/?a=blobdiff_plain;f=main.asm;h=538039b5ab29b0cd402d26105e3df89d3c5f2424;hb=a856c7d5b35de1b48bdd948186ec4a03f7c3685c;hp=e6b0ac280cfc359bbad93881900df086e3e0379e;hpb=4d233157714c21c1c15e7b271460a1692da55f52;p=rrq%2Fjonasforth.git

diff --git a/main.asm b/main.asm
index e6b0ac2..538039b 100644
--- a/main.asm
+++ b/main.asm
@@ -1,5 +1,35 @@
+;; vim: syntax=fasm
+
 format ELF64 executable
 
+;; "Syscalls" {{{
+
+;; [NOTE] Volatile registers Linux (syscalls) vs UEFI
+;;
+;;   Linux syscalls: RAX, RCX, R11
+;;   UEFI:           RAX, RCX, R11, RDX, R8, R9, R10
+
+;; We are in the process of replacing our dependency on Linux with a dependency
+;; on UEFI. The following macros attempt to isolate what would be syscalls in
+;; Linux; thus, we will be able to replace these with UEFI-based implementations,
+;; and in theory we should expect the program to work.
+
+;; Print a string of a given length.
+;;
+;; Input:
+;; - RCX = Pointer to buffer
+;; - RDX = Buffer length
+;;
+;; Clobbers: RAX, RCX, R11, RDI, RSI
+macro sys_print_string {
+  mov rax, 1
+  mov rdi, 1
+  mov rsi, rcx
+  syscall
+}
+
+;; }}}
+
 ;; The code in this macro is placed at the end of each Forth word. When we are
 ;; executing a definition, this code is what causes execution to resume at the
 ;; next word in that definition.
@@ -57,18 +87,12 @@ macro forth_asm label, name, immediate {
 .start:
 }
 
-;; Define a Forth word that is implemented in Forth. (The body will be a list of
-;; 'dq' statements.)
-macro forth label, name, immediate {
-  header label, name, immediate
-  dq DOCOL
-}
-
 segment readable executable
 
 entry main
 
-include "impl.asm"
+include "impl.asm"      ; Misc. subroutines
+include "bootstrap.asm" ; Forth words encoded in Assembly
 
 main:
   cld                        ; Clear direction flag so LODSQ does the right thing.
@@ -161,28 +185,16 @@ forth_asm EXEC, 'EXEC'
 forth_asm EMIT, 'EMIT'
   pushr rsi
   pushr rax
-  mov rax, 1
-  mov rdi, 1
-  lea rsi, [rsp]
+
+  lea rcx, [rsp]
   mov rdx, 1
-  syscall
+  sys_print_string
+
   add rsp, 8
   popr rax
   popr rsi
   next
 
-;; Prints a newline to standard output.
-forth NEWLINE, 'NEWLINE'
-  dq LIT, $A
-  dq EMIT
-  dq EXIT
-
-;; Prints a space to standard output.
-forth SPACE, 'SPACE'
-  dq LIT, ' '
-  dq EMIT
-  dq EXIT
-
 ;; Read a word from standard input and push it onto the stack as a pointer and a
 ;; size. The pointer is valid until the next call to READ_WORD.
 forth_asm READ_WORD, 'READ-WORD'
@@ -208,25 +220,18 @@ forth_asm PARSE_NUMBER, 'PARSE-NUMBER'
   push rax                      ; Result
   next
 
-forth READ_NUMBER, 'READ-NUMBER'
-  dq READ_WORD
-  dq PARSE_NUMBER
-  dq EXIT
-
 ;; Takes a string (in the form of a pointer and a length on the stack) and
 ;; prints it to standard output.
 forth_asm TELL, 'TELL'
-  mov rbx, rsi
-  mov rcx, rax
+  pushr rax
+  pushr rsi
 
-  mov rax, 1
-  mov rdi, 1
-  pop rdx     ; Length
-  pop rsi     ; Buffer
-  syscall
+  pop rdx ; Length
+  pop rcx ; Buffer
+  sys_print_string
 
-  mov rax, rcx
-  mov rsi, rbx
+  popr rsi
+  popr rax
   next
 
 ;; Exit the program cleanly.
@@ -235,16 +240,6 @@ forth_asm TERMINATE, 'TERMINATE'
   mov rdi, 0
   syscall
 
-forth HELLO, 'HELLO'
-  dq LIT, 'H', EMIT
-  dq LIT, 'e', EMIT
-  dq LIT, 'l', EMIT
-  dq LIT, 'l', EMIT
-  dq LIT, 'o', EMIT
-  dq LIT, '!', EMIT
-  dq NEWLINE
-  dq EXIT
-
 ;; Duplicate a pair of elements.
 forth_asm PAIRDUP, '2DUP'
   pop rbx
@@ -279,54 +274,6 @@ forth_asm NOT_, 'NOT'
   push 1
   next
 
-;; The INTERPRET word reads and interprets user input. It's behavior depends on
-;; the current STATE. It provides special handling for integers.
-forth INTERPRET, 'INTERPRET'
-  ;; Read word
-  dq READ_WORD
-  dq PAIRDUP
-  ;; Stack is (word length word length).
-  dq FIND                       ; Try to find word
-  dq DUP_
-  dq ZBRANCH, 8 * 20            ; Check if word is found
-
-  ;; - Word is found -
-
-  dq STATE, GET, ZBRANCH, 8 * 9 ; Check whether we are in compilation or immediate mode
-
-  ;; (Word found, compilation mode)
-  dq DUP_, IS_IMMEDIATE, NOT_, ZBRANCH, 8 * 4 ; If the word is immediate, continue as we would in immediate mode
-
-  ;; Otherwise, we want to compile this word
-  dq TCFA
-  dq COMMA
-  dq EXIT
-
-  ;; (Word found, immediate mode)
-  ;; Execute word
-  dq TCFA
-  ;; Stack is (word length addr)
-  dq SWAP, DROP
-  dq SWAP, DROP
-  ;; Stack is (addr)
-  dq EXEC
-  dq EXIT
-
-  ;; - No word is found, assume it is an integer literal -
-  ;; Stack is (word length addr)
-  dq DROP
-  dq PARSE_NUMBER
-
-  dq STATE, GET, ZBRANCH, 8 * 5 ; Check whether we are in compilation or immediate mode
-
-  ;; (Number, compilation mode)
-  dq LIT, LIT, COMMA
-  dq COMMA
-  dq EXIT
-
-  ;; (Number, immediate mode)
-  dq EXIT
-
 ;; .U prints the value on the stack as an unsigned integer in hexadecimal.
 forth_asm DOTU, '.U'
   mov [.length], 0
@@ -378,11 +325,9 @@ forth_asm DOTU, '.U'
   loop .flip
 
   ;; Print the buffer
-  mov rax, 1
-  mov rdi, 1
-  mov rsi, .buffer
+  mov rcx, .buffer
   mov rdx, [.printed_length]
-  syscall
+  sys_print_string
 
   ;; Restore RSI and continue execution
   pop rsi
@@ -442,31 +387,6 @@ forth_asm TIMESMOD, '/MOD'
   push rdx                      ; a % b
   next
 
-;; Get the location of the STATE variable. It can be set with '!' and read with
-;; '@'.
-forth STATE, 'STATE'
-  dq LIT, var_STATE
-  dq EXIT
-
-;; Get the location of the LATEST variable. It can be set with '!' and read with
-;; '@'.
-forth LATEST, 'LATEST'
-  dq LIT, latest_entry
-  dq EXIT
-
-;; Get the location at which compiled words are expected to be added. This
-;; pointer is usually modified automatically when calling ',', but we can also
-;; read it manually with 'HERE'.
-forth HERE, 'HERE'
-  dq LIT, here
-  dq EXIT
-
-forth COMMA, ','
-  dq HERE, GET, PUT             ; Set the memory at the address pointed to by HERE
-  dq HERE, GET, LIT, 8, PLUS    ; Calculate new address for HERE to point to
-  dq HERE, PUT                  ; Update HERE to point to the new address
-  dq EXIT
-
 ;; Read user input until next " character is found. Push a string containing the
 ;; input on the stack as (buffer length). Note that the buffer is only valid
 ;; until the next call to S" and that no more than 255 character can be read.
@@ -533,36 +453,58 @@ forth_asm CREATE, 'CREATE'
 
   next
 
-;; Mark the last added word as immediate.
-forth IMMEDIATE, 'IMMEDIATE', 1
-  dq LIT, 1
-  dq LATEST, GET
-  dq LIT, 8, PLUS
-  dq PUT_BYTE
-  dq EXIT
+forth_asm TICK, "'"
+  lodsq
+  push rax
+  next
 
-;; Given the address of a word, return 0 if the given word is not immediate.
-forth IS_IMMEDIATE, 'IMMEDIATE?'
-  dq LIT, 8, PLUS
-  dq GET_BYTE
-  dq EXIT
+forth_asm ROT, 'ROT'
+  pop rax
+  pop rbx
+  pop rdx
+  push rax
+  push rdx
+  push rbx
+  next
 
-;; Enter immediate mode, immediately
-forth INTO_IMMEDIATE, '[', 1
-  dq LIT, 0, STATE, PUT_BYTE
-  dq EXIT
+forth_asm PICK, 'PICK'
+  pop rax
+  lea rax, [rsp + 8 * rax]
+  mov rax, [rax]
+  push rax
+  next
 
-;; Enter compilation mode
-forth OUTOF_IMMEDIATE, ']'
-  dq LIT, 1, STATE, PUT_BYTE
-  dq EXIT
+forth_asm EQL, '='
+  pop rax
+  pop rbx
+  cmp rax, rbx
+  je .eq
+.noteq:
+  push 0
+  next
+.eq:
+  push 1
+  next
 
 forth MAIN, 'MAIN'
-  dq HELLO
   dq INTERPRET
   dq BRANCH, -8 * 2
   dq TERMINATE
 
+;; Built-in variables:
+
+forth STATE, 'STATE'
+  dq LIT, var_STATE
+  dq EXIT
+
+forth LATEST, 'LATEST'
+  dq LIT, latest_entry
+  dq EXIT
+
+forth HERE, 'HERE'
+  dq LIT, here
+  dq EXIT
+
 segment readable writable
 
 ;; The LATEST variable holds a pointer to the word that was last added to the
@@ -591,7 +533,7 @@ DOTU.printed_length dq ?
 
 ;; Reserve space for compiled words, accessed through HERE.
 here dq here_top
-here_top rq $2000
+here_top rq $4000
 
 ;; Return stack
 rq $2000