0004555: Compilation of equality involving polymorphic variants not optimized

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Date Submitted

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0004555

OCaml

OCaml general

public

2008-05-19 18:34

2008-08-27 12:24

Reporter

pzimmer

Assigned To

Priority

normal

Severity

minor

Reproducibility

always

Status

closed

Resolution

fixed

Platform

OS Version

Product Version

3.10.2

Target Version

Fixed in Version

3.11+dev

Summary

0004555: Compilation of equality involving polymorphic variants not optimized

Description

The following code:

let f x = x = `Test

generates a call to caml_equal for the comparison. Equivalent code using pattern matching or (==) generates optimized code with an integer comparison. This looks like one trivial optimization case is missing in the compiler.

Here is a proposed patch (contributed by Mark Shinwell) that seems to be correct and fixes the problem:

--- ocaml-3.10.2/bytecomp/translcore.ml 2007-02-09 08:31:15.000000000 -0500
+++ ocaml-3.10.2-patched/bytecomp/translcore.ml 2008-05-16 18:46:48.000076000 -0400
@@ -279,6 +279,12 @@ let transl_prim prim args =
     | [{exp_desc = Texp_construct({cstr_tag = Cstr_constant _}, _)}; arg2]
       when simplify_constant_constructor ->
         intcomp
+ | [arg1; {exp_desc = Texp_variant(_, None)}]
+ when simplify_constant_constructor ->
+ intcomp
+ | [{exp_desc = Texp_variant(_, None)}; exp2]
+ when simplify_constant_constructor ->
+ intcomp
     | [arg1; arg2] when has_base_type arg1 Predef.path_int
                      || has_base_type arg1 Predef.path_char ->
         intcomp

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Notes
(0004511) pzimmer (reporter) 2008-05-28 15:45	Note that I accidentally miscategorized this entry: it should be in "OCaml general" and not in "Caml-light". If one of the admins could fix it, that would be great. Thanks.

(0004588) garrigue (manager) 2008-08-27 12:24	Fixed as suggested in CVS head (for 3.11)

Issue History
Date Modified	Username	Field	Change
2008-05-19 18:34	pzimmer	New Issue
2008-05-28 15:45	pzimmer	Note Added: 0004511
2008-05-28 16:17	doligez	Status	new => acknowledged
2008-05-28 16:17	doligez	Category	Caml-light => OCaml general
2008-08-27 12:24	garrigue	Status	acknowledged => closed
2008-08-27 12:24	garrigue	Note Added: 0004588
2008-08-27 12:24	garrigue	Resolution	open => fixed
2008-08-27 12:24	garrigue	Fixed in Version	=> 3.11+dev