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| author | Kartik Agaram <vc@akkartik.com> | 2020-05-13 00:08:18 -0700 |
|---|---|---|
| committer | Kartik Agaram <vc@akkartik.com> | 2020-05-18 00:44:49 -0700 |
| commit | e5118fa9fb6b1925f785f810767ca642097622d3 (patch) | |
| tree | a6ee4e2dd5b491b9897bca991145d3e9b5455656 /069allocate.subx | |
| parent | 8becbf3c542ecaf2df29ea80cf178921fbc67e82 (diff) | |
| download | mu-e5118fa9fb6b1925f785f810767ca642097622d3.tar.gz | |
handle nulls in lookup
Cleaner abstraction, but adds 3 instructions to our overhead for handles, including one potentially-hard-to-predict jump :/ I wish I could have put the alloc id in eax for the comparison as well, to save a few bytes of instruction space. But that messes up the non-null case.
Diffstat (limited to '069allocate.subx')
| -rw-r--r-- | 069allocate.subx | 40 |
1 files changed, 36 insertions, 4 deletions
diff --git a/069allocate.subx b/069allocate.subx index 2a40866e..31afc4ff 100644 --- a/069allocate.subx +++ b/069allocate.subx @@ -123,6 +123,7 @@ allocate-raw: # ad: (addr allocation-descriptor), n: int, out: (addr handle) 89/copy 0/mod/indirect 2/rm32/edx . . . 0/r32/eax . . # copy eax to *edx # out->payload = ad->curr 8b/copy 0/mod/indirect 1/rm32/ecx . . . 0/r32/eax . . # copy *ecx to eax +$allocate-raw:save-payload-in-eax: 89/copy 1/mod/*+disp8 2/rm32/edx . . . 0/r32/eax 4/disp8 . # copy eax to *(edx+4) # *out->payload = Next-alloc-id 8b/copy 1/mod/*+disp8 2/rm32/edx . . . 7/r32/edi 4/disp8 . # copy *(edx+4) to edi @@ -260,8 +261,13 @@ lookup: # h: (handle T) -> eax: (addr T) 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # . save registers 51/push-ecx + # eax = 0 + 31/xor 3/mod/direct 0/rm32/eax . . . 0/r32/eax . . # clear eax # ecx = handle->alloc_id 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 8/disp8 . # copy *(ebp+8) to ecx + # if (ecx == 0) return 0 + 81 7/subop/compare 3/mod/direct 1/rm32/ecx . . . . . 0/imm32 # compare ecx + 74/jump-if-= $lookup:end/disp8 # eax = handle->address (payload) 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 0xc/disp8 . # copy *(ebp+12) to eax # if (ecx != *eax) abort @@ -295,7 +301,6 @@ test-lookup-success: # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp - # . save registers # var ad/ebx: allocation-descriptor 68/push 0/imm32/limit 68/push 0/imm32/curr @@ -344,9 +349,36 @@ test-lookup-success: 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # clean up c7 0/subop/copy 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 0x100/imm32 # copy to *Next-alloc-id - # . restore registers - 5a/pop-to-edx - 59/pop-to-ecx + # . epilogue + 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp + 5d/pop-to-ebp + c3/return + +test-lookup-null-returns-null: + # . prologue + 55/push-ebp + 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp + # var handle/ecx: handle + 68/push 0/imm32/address + 68/push 0/imm32/alloc-id + 89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx + # eax = lookup(handle) + # . . push args + ff 6/subop/push 1/mod/*+disp8 1/rm32/ecx . . . . 4/disp8 . # push *(ecx+4) + ff 6/subop/push 0/mod/indirect 1/rm32/ecx . . . . . . # push *ecx + # . . call + e8/call lookup/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # check-ints-equal(eax, 0, msg) + # . . push args + 68/push "F - test-lookup-null-returns-null"/imm32 + 68/push 0/imm32 + 50/push-eax + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp |