75 lines
2.2 KiB
ArmAsm
75 lines
2.2 KiB
ArmAsm
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.ifndef _gc_s_file
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_gc_s_file:
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.macro prealloc name amount
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mov %rsp,%rax
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sub _write_region_start, %rax
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cmp $amount, %rax #TODO check direction
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jb _uskel_gc
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.endm
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_uskel_alloc:
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mov %rsi, %r15 # %rsi is the return address; back it up
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# calculate the desired size to %r14
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mov _gc_min_alloc, %r14
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# check if the desired size isn't greater because of the last gc use
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mov _gc_last_size, %rax
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mul _gc_min_expect_ratio, %rax
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shr 8, %rax
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cmp %r14, %rax #TODO check direction
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cmova %rax, %r14
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# check if we don't need even more space because we need to evacuate stuff
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mov _gc_region_end, %rax
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sub %rsp, %rax # trick -- if we counted from gc region start, allocated memory could never shrink
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cmp %r14, %rax #TODO direction
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cmova %rax, %r14
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#TODO add functionality to trigger the gc's a bit earlier than when
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# they hit _write_region_start, to allow for faster compaction.
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# maybe _write_region_trigger = 25%ish between _write_region_start and %rsp ?
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mov $9, %rax # mmap
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mov $0, %rdi # addr = NULL
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mov %r14, %rsi # len = %r14
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mov $0b11, %rdx # prot = PROT_READ 0b1 | PROT_WRITE 0b10
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mov $0x22, %r10 # flags = MAP_PRIVATE 0x2 | MAP_ANONYMOUS 0x20
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mov $-1, %r8 # fd = -1
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mov $0, %r9 # off = 0
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syscall
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# store the results
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mov %rax, _write_region_start
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add %r14, %rax
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mov %rax, _write_region_end
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mov %rax, %rsp # initialize writing into the new region
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jmp *%r15
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_uskel_gc:
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mov %rbp, _gc_backup_thunk
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mov %rsi, _gc_backup_cont
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# first we need a new memory area
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mov _write_region_start, _gc_region_start
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mov _write_region_end, _gc_region_end
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mov $_uskel_gc_evacuate, %r15
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jmp _uskel_alloc
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_uskel_gc_evacuate:
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# we may also need a scavenging queue! Or can that be solved by walking the write region?
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# plan:
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# evacuate thunk and cont, save them right away in _gc_backup_thunk and _cont
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# scavenge from the top of the gc region, evacuating stuff en route
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# (this is a little more complex because we grow down, so we have to
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# scavenge up from %rsp to the last known scavenged position)
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# finish when scavenge doesn't have anything more to scavenge
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# save how much data we actually had at this point
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mov _write_region_end, _gc_last_size
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sub %rsp, _gc_last_size
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enter_rbp # restart the thunk for simplicity
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.endif #_gc_s_file
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