debug the gc

3 files changed, 67 insertions, 55 deletions

diff --git a/include/data.s b/include/data.s
index 3ee8213..575b4ae 100644
--- a/include/data.s
+++ b/include/data.s
@@ -1,6 +1,7 @@
 
 .ifndef _data_s_file
 _data_s_file:
+	nop
 
 # Format of the info tables:
 # - code
@@ -10,18 +11,21 @@ _data_s_file:
 # - 8B pointer to evacuate
 #
 # Evacuate interface:
-# in: %rsi continuation, %rbp what to evacuate
+# in: %rbp what to evacuate
 # out: %rbp where the thing is now
+# ret: jump to _gc_evacuate_ret
 # Notes:
 #  - IND thunks skip themselves on evacuate
-#  - checking if whether stuff is already in write region are managed by _gc_evacuate prelude
+#  - checking if whether stuff is already in write region are managed by
+#  _gc_evacuate prelude
 #
 # Scavenge interface:
-# in: %rsi continuation, %rbp what to scavenge
+# in: %rbp what to scavenge
 # out: %rbp next thing to scavenge in memory
+# ret: jump to _gc_scavenge_ret
 #
-# Saved registers by evacuate and scavenge
-# - _uskel_gc needs to preserve %rdi now; that might increase
+# Saved registers during the GC process:
+# - _uskel_gc uses %r8-%r11
 # - scavenges use %r12-%r15
 # - %rax-%rdx is scratch and evacuate use
 
@@ -31,10 +35,10 @@ INT_evacuate:
 	pushq 010(%rbp)
 	pushq $INT_code
 	mov %rsp,%rbp
-	jmp *%rsi
+	jmp _gc_evacuate_ret
 INT_scavenge:
 	add $020, %rbp
-	jmp *%rsi
+	jmp _gc_scavenge_ret
 
 INT_info_table:
 	cell INT_evacuate
@@ -49,7 +53,9 @@ IND_evacuate:
 	mov 010(%rbp), %rbp
 	jmp _gc_evacuate
 IND_scavenge:
-	jmp 0 # thou shalt not scavenge here
+	# this should never be triggered but let's play it safe
+	add $020, %rbp
+	jmp _gc_scavenge_ret
 
 IND_info:
 	cell IND_evacuate
@@ -69,17 +75,17 @@ LIST_evacuate:
 	pushq $1
 	pushq $LIST_code
 	mov %rsp, %rbp
-	jmp *%rsi
+	jmp _gc_evacuate_ret
+
 	LIST_evacuate_nil:
 	pushq $0
 	pushq $LIST_code
 	mov %rsp, %rbp
-	jmp *%rsi
+	jmp _gc_evacuate_ret
 LIST_scavenge:
 	cmpq $0, 010(%rbp)
 	je LIST_scavenge_nil
 	mov %rbp, %r15
-	mov %rsi, %r14
 	
 	mov $LIST_scavenge1, %rsi
 	mov 020(%r15), %rbp
@@ -95,10 +101,11 @@ LIST_scavenge:
 
 	mov %r15, %rbp
 	add $040, %rbp
-	jmp *%r14
+	jmp _gc_scavenge_ret
+
 	LIST_scavenge_nil:
 	add $020, %rbp
-	jmp *%rsi
+	jmp _gc_scavenge_ret
 
 LIST_info_table:
 	cell LIST_evacuate
@@ -160,15 +167,14 @@ FUN4_code:
 # | ptr | args | arg[0] | arg[1] | ... | arg[args] |
 # args wouldn't need to be here but let's keep them for gc simplicity
 THU_evacuate:
-	mov 010(%rbp), %rbx
-	mov %rbx,%rdx
-	mov %rbx,%rcx
+	mov 010(%rbp), %rbx # rbx = count of arguments
+	mov %rbx, %rdx
+	mov %rbx, %rcx # rcx = count of arguments for later looping
 	add $2, %rdx
 	shl $3, %rdx
-	add %rbp, %rdx
+	add %rbp, %rdx # rdx = address of the argument
 	THU_evacuate_one:
-	dec %rcx
-	cmp $0, %rcx
+	sub $1, %rcx
 	jl THU_evacuate_fini
 	sub $010, %rdx
 	pushq (%rdx)
@@ -177,32 +183,32 @@ THU_evacuate:
 	pushq %rbx
 	pushq 000(%rbp)
 	mov %rsp, %rbp
-	jmp *%rsi
+	jmp _gc_evacuate_ret
 THU_scavenge:
-	mov 010(%rbp), %r12
-	mov %rbp, %r15
-	mov %rsi, %r14
-	mov %r12,%r13
-	add $2, %r13
-	shl $3, %r13
-	add %r15, %r13
+	mov 010(%rbp), %r13 # r13 = count of arguments (for looping)
+	mov %rbp, %r15 # r15 = scavengee ptr
+	mov %r13,%r14
+	add $2, %r14
+	shl $3, %r14
+	add %r15, %r14 # r14 = address of argument
+
 	THU_scavenge_one:
-	sub $010, %r13
-	sub $1, %r12
+	sub $1, %r13
 	jl THU_scavenge_fini
-	mov (%r13), %rbp
+	sub $010, %r14
+	mov (%r14), %rbp
 	mov $THU_scavenge_one_cont, %rsi
 	jmp _gc_evacuate
 	THU_scavenge_one_cont:
-	mov %rbp, (%r13)
+	mov %rbp, (%r14)
 	jmp THU_scavenge_one
 
 	THU_scavenge_fini:
-	mov %r15, %rbp
-	mov 010(%rbp), %r13
-	add $2, %r13
-	shl $3, %r13
-	add %r13, %rbp
-	jmp *%r14
+	mov %r15, %rbp # restore rbp
+	mov 010(%rbp), %r14
+	add $2, %r14
+	shl $3, %r14 # r14 is size of object
+	add %r14, %rbp # move rbp to next rbp
+	jmp _gc_scavenge_ret
 
 .endif # _data_s_file
diff --git a/include/gc.s b/include/gc.s
index 636a6a2..ae71d5c 100644
--- a/include/gc.s
+++ b/include/gc.s
@@ -74,6 +74,8 @@ _uskel_alloc:
 	cmp %r14, %rax
 	cmova %rax, %r14
 
+	and $0xfffffffffffffff8, %r14 #align
+
 	alloc_goes_mmap:
 	mov $9, %rax # mmap
 	mov $0, %rdi # addr = NULL
@@ -94,7 +96,7 @@ _uskel_alloc:
 
 _uskel_gc_init:
 	mov %rsi, %r13
-	movq $0x100, _gc_min_alloc
+	movq $0x100, _gc_min_alloc # must be higher than 2x the biggest thunk possible
 	movq $0x180, _gc_grow_ratio
 	movq $0x40, _gc_shrink_ratio
 	mov $0, %rsp # fake original rsp for first alloc run
@@ -121,7 +123,7 @@ _uskel_gc:
 
 	# point the writer to the new memory area
 	mov _write_region_end, %rsp
-	mov %rsp, %rdi # %rdi is "the last scavenged thing"
+	mov %rsp, %r8 # % r8 is the "last thing that was scavenged"
 	
 	# start by evacuating the thunk and cont
 	mov _gc_backup_thunk, %rbp
@@ -139,27 +141,26 @@ _uskel_gc:
 	# scavenge everything
 	_uskel_gc_scavenge:
 	# start at what we wrote last
-	mov %rsp, %rbp
+	mov %rsp, %rbp # rbp is the iterator (conveniently)
+	mov %rsp, %r9 # % r9 stores where we started with this evacuate round
 
 	# if the thing is already scavenged, we didn't write anything, mark done.
-	cmp %rbp, %rdi
+	cmp %rbp, %r8
 	jbe _uskel_gc_scavenge_end
 
 	_uskel_gc_scavenge1:
 	# if all ok, scavenge one thing (moving %rbp) and recheck
-	mov $_uskel_gc_scavenge1_ret, %rsi
 	mov (%rbp), %rax
 	jmp *-020(%rax) # scavenge position in infotable
-	_uskel_gc_scavenge1_ret:
-	cmp %rbp, %rdi
+	_gc_scavenge_ret:
+	cmp %rbp, %r8
 	ja _uskel_gc_scavenge1
 
-	# everything above rsp is now scavenged, continue with next round
-	mov %rsp, %rdi
+	# everything above r9 is now scavenged, continue with next round
+	mov %r9, %r8 # we started at r9, so that is now "done"
 	jmp _uskel_gc_scavenge
 
 	_uskel_gc_scavenge_end:
-
 	# deallocate the old memory region
 	mov $11, %rax # munmap
 	mov _gc_region_end, %rsi
@@ -188,14 +189,22 @@ _uskel_gc:
 _gc_evacuate:
 	# check if we are really out of the target region
 	cmp _write_region_start, %rbp
-	jb _gc_evacuate_ok
+	jb _gc_evacuate_go
 	cmp _write_region_end, %rbp
-	jae _gc_evacuate_ok
+	jae _gc_evacuate_go
+	_gc_evacuate_skip:
 	# if not, let's just jump to cont and leave %rbp as result
 	jmp *%rsi
-	_gc_evacuate_ok:
+	_gc_evacuate_go:
 	# if we should evacuate, jump to the evac routine
+	mov %rbp, %r10
 	mov (%rbp), %rax
 	jmp *-030(%rax)
+	_gc_evacuate_ret:
+	# install the indirection
+	movq $IND_code, 000(%r10)
+	mov %rbp, 010(%r10)
+	jmp *%rsi
+
 
 .endif #_gc_s_file
diff --git a/include/main_exit.s b/include/main_exit.s
index 1a38e5a..5ce6c76 100644
--- a/include/main_exit.s
+++ b/include/main_exit.s
@@ -1,13 +1,10 @@
 .ifndef _main_exit_s_file
 _main_exit_s_file:
 
-# exitcode -> | cont (unused, should be 0) |
+# exitcode -> ||
 .thunkcode main_exit
-	mov 010(%rsi), %rdi # result goes to syscall exitcode
+	mov 010(%rsi), %rdi # result INT goes to syscall exitcode
 	mov $60, %rax  # exit=60
 	syscall # exit %rdi
 
-# TODO this is a "case" kind of thunk so it's quite likely that it really
-# doesn't need the continuation.
-
 .endif # _main_exit_s_file