0005580: Inlining misses some simple simplifications

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0005580

OCaml

OCaml backend (code generation)

public

2012-04-09 18:30

2012-09-21 14:14

Reporter

jfc

Assigned To

Priority

normal

Severity

minor

Reproducibility

always

Status

acknowledged

Resolution

open

Platform

x86-64

Linux

OS Version

Product Version

3.12.1

Target Version

4.01.0+dev

Fixed in Version

Summary

0005580: Inlining misses some simple simplifications

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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Issue History
Date Modified	Username	Field	Change
2012-04-09 18:30	jfc	New Issue
2012-04-10 15:55	doligez	Status	new => acknowledged
2012-07-09 17:39	doligez	Target Version	=> 4.01.0+dev
2012-07-31 13:36	doligez	Target Version	4.01.0+dev => 4.00.1+dev
2012-09-21 14:14	doligez	Target Version	4.00.1+dev => 4.01.0+dev