move to STC forth, note on COMPILE,

2 files changed, 28 insertions, 7 deletions

diff --git a/jefs.s b/jefs.s
index d698f13..eca2374 100644
--- a/jefs.s
+++ b/jefs.s
@@ -6,9 +6,17 @@
 %assign	__NR_brk	12
 %assign	__NR_exit	60
 
+section .bss
+wstack_b:	resq 2047
+wstack:		resq 1
+
 section .text
 global _start
 _start:
+	; init
+	mov r14, wstack
+	xor r15, r15
+
 	mov rdi, 0
 	mov rax, __NR_exit
 	syscall
diff --git a/readme.md b/readme.md
index 03b19f0..5d6ab77 100644
--- a/readme.md
+++ b/readme.md
@@ -5,18 +5,31 @@ if you use it and it breaks, too bad
 
 public domain
 
-the plan right now is that this will be a DTC forth.
-while an STC forth would be nice
-(being able to mix assembly and forth would be nice)
-having to manually compile in bytes would be annoying.
-maybe one day i will do an STC forth...
+the plan right now is that this will be an STC forth.
+if this proves Too Complicated To Deal With the plan may be changed
+to a DTC forth instead.
 
 ## forth registers
 there are a set of 'virtual registers' (see moving forth part 1)
 
 - W, the working register, is r11.
 - X, the secondary working register, is r12.
-- IP, the instruction pointer, is r13.
+- IP, the instruction pointer, is r13. (this will only be needed if we switch to DTC, otherwise this can be Y, a third general purpose register)
 - SP, the working stack pointer, is r14.
-- RSP, the return stack pointer, is rsp.
 - TOS, the top of the stack, is r15.
+- RSP, the return stack pointer, is rsp.
+
+on SP (r14): note that since TOS is kept in a register,
+SP points to the *second* item in the stack.
+
+## miscellaneous notes and stuff
+
+### COMPILE,
+this is an STC forth so when we compile a call we have to
+write the bytes of a `call` in manually.
+x86\_64 does not allow absolute jumps from an immediate address,
+so a wonky but hopefully not too slow solution is to compile
+`literal address → W` and then `call W`. It'll Be Fine?
+
+- `mov r11, [cfa] = `94 BB [CFA]`
+- `call r11` = `41 FF D3`