From cff9c9ce7df4e9c09c64a7cdf64859a06588d6be Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maja=20K=C4=85dzio=C5=82ka?= <maya@compilercrim.es>
Date: Thu, 13 Apr 2023 18:47:17 +0200
Subject: [PATCH] Move EMIT out of the kernel, saving 12 bytes

---
 README.md            |  8 +++-----
 blocks/bootstrap.fth |  6 +++---
 boot.s               | 24 ++++++++++--------------
 3 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/README.md b/README.md
index 8e26fdd..578059f 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@
 The following standard words are available:
 
 ```
-- ! @ c! c@ dup swap emit u. >r r> : ; load
+- ! @ c! c@ dup swap u. >r r> : ; load
 ```
 
 Additionally, there are two non-standard words.
@@ -181,8 +181,8 @@ Git or GitHub's web interface. This disparity is handled by two Python scripts:
 
 ## Free bytes
 
-At this moment, not counting the `55 AA` signature at the end, **462** bytes are used,
-leaving 48 bytes for any potential improvements.
+At this moment, not counting the `55 AA` signature at the end, **450** bytes are used,
+leaving 60 bytes for any potential improvements.
 
 Byte saving leaderboard:
  - Ilya Kurdyukov saved 24 bytes. Thanks!
@@ -191,8 +191,6 @@ Byte saving leaderboard:
 
 If a feature is strongly desirable, potential tradeoffs include:
 
- - 12 bytes: Remove the `emit` word - we need loops to make good use of it, and
-   by that point we can assemble it ourselves.
  - 7 bytes: Don't push the addresses of variables kept by self-modifying code. This
    essentially changes the API with each edit (NOTE: it's 7 bytes because this makes it
    beneficial to keep `>IN` in the literal field of an instruction).
diff --git a/blocks/bootstrap.fth b/blocks/bootstrap.fth
index 3516fc9..4cd6ce8 100644
--- a/blocks/bootstrap.fth
+++ b/blocks/bootstrap.fth
@@ -47,8 +47,7 @@ variable pos                    : pos, pos @ ! 2 pos +! ;
 : [  1 st c! ; immediate        : ]  0 st c! ;               -->
 
 : rep, F2 c, ;    : cld, FC c, ;    : std, FD c, ;
-: cmpsb, A6 c, ;  : cmpsw, A7 c, ;
-: notw-r, F7 c, 2 rm-r, ;
+: cmpsb, A6 c, ;  : cmpsw, A7 c, ;  : notw-r, F7 c, 2 rm-r, ;
 : [bx+si] 0 ;  : [bx+di] 1 ;  : [bp+si] 2 ;  : [bp+di] 3 ;
 : [si] 4 ;  : [di] 5 ;  : [#] 6 ;  : [bp] 6 ;  : [bx] 7 ;
 : m-r, 3shl + c, ;              : r-m, swap m-r, ;
@@ -56,10 +55,11 @@ variable pos                    : pos, pos @ ! 2 pos +! ;
 :code or   ax pop,  ax bx orw-rr,   next,
 :code and  ax pop,  ax bx andw-rr,  next,
 :code xor  ax pop,  ax bx xorw-rr,  next,
+:code emit  bx ax movw-rr,  0E ah movb-ir,  bx bx xorw-rr,
+  10 int,   bx pop,  next,
 : jz, 74 c, ;   : jnz, 75 c, ;
 : j> here 0 c, ;  : >j dup >r 1 + here swap - r> c! ;
 : j< here ;       : <j here 1 + - c, ;
-
 : :cmp  :code  ax ax xorw-rr, ;
 : cmp;  j> ax decw, >j  ax bx movw-rr,  next, ;              -->
 :cmp 0=  bx bx orw-rr, jnz, cmp;
diff --git a/boot.s b/boot.s
index 1ca96fa..6bd2998 100644
--- a/boot.s
+++ b/boot.s
@@ -119,13 +119,17 @@ ReadLine:
     db 0x3c          ; mask next instruction
 .write:
     stosb
-    call PutChar
+
+    xor bx, bx
+    mov ah, 0x0e
+    int 0x10
+
     cmp al, 0x0d
     jne short .loop
 .enter:
     mov al, 0x0a
     int 0x10
-    mov [di-1], bl ; write the null terminator by using the BX = 0 from PutChar
+    mov [di-1], bl ; BX = 0 at this point
     pop bx
 InterpreterLoopSaveBX:
     push bx
@@ -231,12 +235,6 @@ ParseWord:
     lodsb
     jmp short .takeloop
 
-PutChar:
-    xor bx, bx
-    mov ah, 0x0e
-    int 0x10
-    ret
-
 DiskPacket:
     db 0x10, 0
 .count:
@@ -311,11 +309,6 @@ defcode FROM_R, "r>"
     push bx
     mov bx, [di]
 
-defcode EMIT, "emit"
-    xchg bx, ax
-    call PutChar
-    pop bx
-
 defcode UDOT, "u."
     ; the hexdigit conversion algo below turns 0x89 into a space.
     ; 0x89 itself doesn't fit in a signed 8-bit immediate that
@@ -336,7 +329,10 @@ defcode UDOT, "u."
     adc al, 0x40
     daa
 
-    call PutChar
+    xor bx, bx
+    mov ah, 0x0e
+    int 0x10
+
     cmp al, " "
     jne short .print
     pop bx