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Ensure that comballoc.ml does not reverse the order of allocations #1917

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merged 2 commits into from Nov 14, 2018
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Ensure that comballoc.ml does not reverse the order of allocations #1917

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07a27d2
Ensure that comballoc.ml does not reverse the order of allocations.
stedolan Jul 19, 2018
6b2a8e1
Coding style changes to comballoc.ml.
stedolan Nov 14, 2018
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3 changes: 3 additions & 0 deletions Changes
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Expand Up @@ -299,6 +299,9 @@ Working version
stubs on 32bits
(Jérémie Dimino)

- GPR#1917: comballoc: ensure object allocation order is preserved
(Stephen Dolan)

### Runtime system:

- MPR#7198, MPR#7750, GPR#1738: add a function (caml_custom_alloc_mem)
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51 changes: 26 additions & 25 deletions asmcomp/comballoc.ml
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Expand Up @@ -18,41 +18,42 @@
open Mach

type allocation_state =
No_alloc (* no allocation is pending *)
| Pending_alloc of Reg.t * int (* an allocation is pending *)
(* The arguments of Pending_alloc(reg, ofs) are:
reg the register holding the result of the last allocation
ofs the alloc position in the allocated block *)
No_alloc
| Pending_alloc of
{ reg: Reg.t; (* register holding the result of the last allocation *)
totalsz: int } (* amount to be allocated in this block *)

let allocated_size = function
No_alloc -> 0
| Pending_alloc(_, ofs) -> ofs
| Pending_alloc {totalsz; _} -> totalsz

let rec combine i allocstate =
match i.desc with
Iend | Ireturn | Iexit _ | Iraise _ ->
(i, allocated_size allocstate)
| Iop(Ialloc { bytes = sz; _ }) ->
begin match allocstate with
No_alloc ->
let (newnext, newsz) =
combine i.next (Pending_alloc(i.res.(0), sz)) in
(instr_cons_debug (Iop(Ialloc {bytes = newsz; spacetime_index = 0;
label_after_call_gc = None; }))
i.arg i.res i.dbg newnext, 0)
| Pending_alloc(reg, ofs) ->
if ofs + sz < Config.max_young_wosize * Arch.size_addr then begin
let (newnext, newsz) =
combine i.next (Pending_alloc(reg, ofs + sz)) in
(instr_cons (Iop(Iintop_imm(Iadd, ofs))) [| reg |] i.res newnext,
newsz)
end else begin
let (newnext, newsz) =
combine i.next (Pending_alloc(i.res.(0), sz)) in
(instr_cons_debug (Iop(Ialloc { bytes = newsz; spacetime_index = 0;
label_after_call_gc = None; }))
i.arg i.res i.dbg newnext, ofs)
end
| Pending_alloc {reg; totalsz}
when totalsz + sz < Config.max_young_wosize * Arch.size_addr ->
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Q: Why is the multiplication by Arch.size_addr here? (Yes, I know it was there before...)

A: It looks like I messed up when adding the inline record field called words. It should be called bytes instead. I will make a pull request to fix this. (This shows the value of inline record fields rather than anonymous constructor arguments, especially when units of measure are concerned that do not have their own types.)

let (next, totalsz) =
combine i.next
(Pending_alloc { reg = i.res.(0); totalsz = totalsz + sz }) in
(instr_cons_debug (Iop(Iintop_imm(Iadd, -sz)))
[| reg |] i.res i.dbg next,
totalsz)
| No_alloc | Pending_alloc _ ->
let (next, totalsz) =
combine i.next
(Pending_alloc { reg = i.res.(0); totalsz = sz }) in
let next =
let offset = totalsz - sz in
if offset = 0 then next
else instr_cons_debug (Iop(Iintop_imm(Iadd, offset))) i.res
i.res i.dbg next
in
(instr_cons_debug (Iop(Ialloc {bytes = totalsz; spacetime_index = 0;
label_after_call_gc = None; }))
i.arg i.res i.dbg next, allocated_size allocstate)
end
| Iop(Icall_ind _ | Icall_imm _ | Iextcall _ |
Itailcall_ind _ | Itailcall_imm _) ->
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