From 8504d72bda94c3a1668ebbdd262ae8a4963a23c1 Mon Sep 17 00:00:00 2001
From: Mirek Kratochvil <exa.exa@gmail.com>
Date: Sun, 29 Oct 2023 23:03:33 +0100
Subject: gc attempt 1 (to be cont'd)

---
 include/uskel.s | 79 +++++++++++++++++++++++++++++++++++----------------------
 1 file changed, 49 insertions(+), 30 deletions(-)

(limited to 'include/uskel.s')

diff --git a/include/uskel.s b/include/uskel.s
index 34ee63a..bca33c9 100644
--- a/include/uskel.s
+++ b/include/uskel.s
@@ -8,41 +8,57 @@ _start:
 
 .include "include/macros.s"
 
+# this has globals
 .section .bss
-_memory_state:
-	cell 0 # bottom of allocation (grows down)
-	cell 0 # region start
-	cell 0 # region end
-	cell 0 # program entry rsp (aka the actual stack)
+_unix_rsp:
+	# back-up of program entry rsp (aka the actual stack given by the
+	# actual OS; we might like to use it at some point, maybe)
+	cell 0
+_write_region_start:
+	# begin of the active memory area
+	cell 0
+_write_region_end:
+	# end of the active memory area (%rsp kinda starts here and goes down
+	# towars the start)
+	cell 0
+_gc_last_size:
+	# how much data we evacuated last time
+	cell 0
+_gc_min_alloc:
+	# minimum possible allocation
+	cell 0x100000 # tunable constant
+_gc_min_expect_ratio:
+	# 256th's of the minimal amount of memory increment compared to the
+	# last time. New minimal amount is compared as:
+	# (ratio * last size) >> 8
+	cell 0x200 # tunable constant
+_gc_region_start:
+	# in GC, this region is being evacuated and will eventually disappear
+	cell 0
+_gc_region_end:
+	# end of the disappear region
+	cell 0
+_gc_backup_thunk:
+	# backup of %rsi so that we can use the register for other nonsense
+	cell 0
+_gc_backup_cont:
+	# backup of %rbp for same reason
+	cell 0
 
 .section .text
 
-_uskel_alloc_basic_mem:
-	mov $0x100000, %r15 # desired size
-
-	mov $9, %rax # mmap
-	mov $0, %rdi # addr = NULL
-	mov %r15, %rsi # len = %rcx
-	mov $0b11, %rdx # prot = PROT_READ 0b1 | PROT_WRITE 0b10
-	mov $0x22, %r10 # flags = MAP_PRIVATE 0x2 | MAP_ANONYMOUS 0x20
-	mov $-1, %r8 # fd = -1
-	mov $0, %r9 # off = 0
-	syscall
-	mov $_memory_state, %rdi
-	mov %rax, 010(%rdi)
-	add %r15, %rax
-	mov %rax, (%rdi)
-	mov %rax, 020(%rdi)
-	retq
+.include "include/gc.s"
 
 _uskel_start:
-	call _uskel_alloc_basic_mem
-	# use the stack pointer for easy writing to the heap,
-	# but back it up to memory state
-	mov $_memory_state, %rdi
-	mov %rsp, 030(%rdi)
-	mov 0(%rdi), %rsp
+	# we use the stack pointer for easy writing to the heap;
+	# back it up to memory state just if we ever needed it again.
+	mov %rsp, _unix_rsp
 
+	# allocate the initial chunk of memory
+	mov $_uskel_start_main, %rsi
+	jmp _uskel_alloc
+
+	_uskel_start_main:
 	# push a thunk for main
 	pushq $0
 	pushq $main
@@ -50,5 +66,8 @@ _uskel_start:
 	mov $0, %rsi # set continuation to exit
 	enter %rsp # run the program
 	# Q: are there gonna be functions that have both the argument AND the cont?
-	# A: No, stuff is either entered as return-continuation (takes res, cont has to be saved) or as forward call (takes cont)
-	# (needs validation)
+	# 
+	# A: No, stuff is either entered as return-continuation (takes res,
+	# cont has to be saved) or as forward call (takes cont)
+	#
+	# (A needs validation)
-- 
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