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Inlining misses some simple simplifications #5580

vicuna opened this issue Apr 9, 2012 · 1 comment

Inlining misses some simple simplifications #5580

vicuna opened this issue Apr 9, 2012 · 1 comment


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@vicuna vicuna commented Apr 9, 2012

Original bug ID: 5580
Reporter: jfc
Assigned to: @xavierleroy
Status: closed (set by @xavierleroy on 2015-12-11T18:19:30Z)
Resolution: fixed
Priority: normal
Severity: minor
Platform: x86-64
OS: Linux
Version: 3.12.1
Target version: 4.01.0+dev
Fixed in version: 4.01.0+dev
Category: back end (clambda to assembly)
Monitored by: @hcarty

Bug description

Consider this program:

type t = False | True
let of_bool = function true -> True | false -> False
let x = of_bool true

x should be assigned the constant True but ocamlopt generates a runtime comparison (true != false) to decide the result of of_bool.

Closure.simplif_prim_pure receives the arguments

p = Pintcomp Cneq
approxs = [Value_constptr 1; Value_integer 0]

If both approximations were Value_integer the comparison would be simplified.
The function does not know how to compare a constptr and an integer.

If I change simplif_prim_pure to add a case matching [Value_constptr x; Value_integer y] similarly to [Value_integer x; Value_integer y] code generation improves. I don't understand the compiler well enough to know if that is the correct solution.

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@vicuna vicuna commented Jun 7, 2013

Comment author: @xavierleroy

Improved constant propagation in commit r13754. Will be in release 4.01.

@vicuna vicuna closed this Dec 11, 2015
@vicuna vicuna added this to the 4.01.0 milestone Mar 14, 2019
@vicuna vicuna added the bug label Mar 20, 2019
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