ocamlopt -g misses optimizations #5313
Comments
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Comment author: meyer This is not longer happening on trunk with r11307: $ ../../bin/ocamlopt -g -dlambda -c opt.ml: |
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Comment author: meyer I suspect it was fixed on trunk with #5205 @ r11085.. Could you confirm it's been fixed with the current trunk? |
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Comment author: @ygrek Yes, this exact use case is fixed, thanks! But I am not sure that using -g will not prevent other optimizations cause looking at the code it seems that some optimization passes take -g option into the consideration. Actually, initially I wanted to clarify the meaning of -g and this specific example was the easiest to spot. So is it expected for -g to influence the generated code? |
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Comment author: meyer Reopening, as one place in the code needs better handling of -g flag |
Original bug ID: 5313
Reporter: @ygrek
Assigned to: meyer
Status: closed (set by @xavierleroy on 2012-09-25T18:07:21Z)
Resolution: fixed
Priority: normal
Severity: major
Version: 3.12.0
Fixed in version: 3.13.0+dev
Category: ~DO NOT USE (was: OCaml general)
Related to: #5426
Monitored by: @gasche tgazagna "Dmitry Grebeniuk" thelema @jberdine @Chris00 gerd
Bug description
$ cat opt.ml
let x = ref 0 in
for i = 1 to 10 do
x := !x + i
done
$ /opt/ocaml-3.12.1/bin/ocamlopt -dlambda -c opt.ml
(seq (let (x/1030 0) (for i/1031 1 to 10 (assign x/1030 (+ x/1030 i/1031))))
0a)
$ /opt/ocaml-3.12.1/bin/ocamlopt -g -dlambda -c opt.ml
(seq
(let (x/1030 (makemutable 0 0))
(before 17-54
(for i/1031 1 to 10
(before 38-49 (setfield_imm 0 x/1030 (+ (field 0 x/1030) i/1031))))))
0a)
When using -g int ref is allocated on the heap. This is rather surprising - I expected -g to only add debugging symbols and not prevent optimizations.
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