Skip to content

GitLab

  • Menu
Projects Groups Snippets
  • Help
    • Help
    • Support
    • Community forum
    • Submit feedback
  • Sign in / Register
  • GHC GHC
  • Project information
    • Project information
    • Activity
    • Labels
    • Members
  • Repository
    • Repository
    • Files
    • Commits
    • Branches
    • Tags
    • Contributors
    • Graph
    • Compare
    • Locked Files
  • Issues 4,930
    • Issues 4,930
    • List
    • Boards
    • Service Desk
    • Milestones
    • Iterations
  • Merge requests 461
    • Merge requests 461
  • CI/CD
    • CI/CD
    • Pipelines
    • Jobs
    • Schedules
    • Test Cases
  • Deployments
    • Deployments
    • Releases
  • Analytics
    • Analytics
    • Value stream
    • CI/CD
    • Code review
    • Insights
    • Issue
    • Repository
  • Wiki
    • Wiki
  • Snippets
    • Snippets
  • Activity
  • Graph
  • Create a new issue
  • Jobs
  • Commits
  • Issue Boards
Collapse sidebar
  • Glasgow Haskell Compiler
  • GHCGHC
  • Issues
  • #8668
Closed
Open
Created Jan 14, 2014 by Eric Crockett@crockeeaReporter

SPECIALIZE silently fails to apply

I have a small example where GHC refuses to specialize a call to (+), compiling with -O2. The two files are Foo.hs (http://lpaste.net/98464) and Main.hs (http://lpaste.net/98342).

There seem to be two problems:

  1. The active SPECIALIZE pragma should be applied, but isn't. This can be seen by comparing the core and runtimes of fcTest (slow) vs vtTest (fast). I need this version of the pragma in my real code as the phantom type m is reified, so I need to specialize the vector code without specifying the phantom type.
  2. I can get fcTest to run fast if I use the commented-out SPECIALIZE pragma instead. However, that pragma seems very straightforward to me (all types are concrete). The docs indicate that GHC should automatically specialize in most cases, why does it not specialize to the commented-out signature automatically?

This problem is also posted here: http://stackoverflow.com/questions/21071706/specialization-with-constraints

Trac metadata
Trac field Value
Version 7.6.2
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information
Assignee
Assign to
Time tracking