primops: Add comment describing type of atomicModifyMutVar#
authorBen Gamari <bgamari.foss@gmail.com>
Mon, 6 Mar 2017 22:31:20 +0000 (17:31 -0500)
committerBen Gamari <ben@smart-cactus.org>
Mon, 6 Mar 2017 23:51:04 +0000 (18:51 -0500)
commitd91b10458885aede47ff17fa649b2c0fd9fdf3ca
treef3b028a26a5fc07b6ab668b7dd8c20abc076af0d
parent1686f30951292e94bf3076ce8b3eafb0bcbba91d
primops: Add comment describing type of atomicModifyMutVar#

This resolves #13130. It's not entirely clear to me why we don't use an
unboxed tuple here but this is at least better than the status quo.

[skip ci]

Test Plan: Read it

Reviewers: simonmar, austin, dfeuer

Reviewed By: dfeuer

Subscribers: dfeuer, rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3288
compiler/prelude/primops.txt.pp