go: cmd/compile: compilation of a package >100x slower with 1.20rc3

The package in question is https://github.com/benoitkugler/textlayout/fonts/glyphsnames in v0.3.0, with go 1.19:

$ go version
go version go1.19.1 linux/amd64
$ time go build

real	0m4,086s
user	0m5,970s
sys	0m0,447s

with go 1.20rc3 I got bored of waiting after 10 minutes, so it’s at least 100x slower, but possibly a lot more (for all I know it could be in an infinite loop).

The code in question seems to have some very large (and very questionable) switch statements.

About this issue

Original URL
State: closed
Created a year ago
Comments: 16 (12 by maintainers)

Commits related to this issue

Revert "cmd/compile: teach prove about bitwise OR operation" This reverts commit 3680b5e9c4f42fcf9155aa42b3b344d1fbe19571. Reason for revert: causes long compile times on certain functions. See issu... — committed to golang/go by randall77 a year ago
[release-branch.go1.20] Revert "cmd/compile: teach prove about bitwise OR operation" This reverts commit 3680b5e9c4f42fcf9155aa42b3b344d1fbe19571. Reason for revert: causes long compile times on cer... — committed to golang/go by randall77 a year ago
cmd/compile: teach prove about bitwise OR operation For now, only apply the rule if either of arguments are constants. That would catch a lot of real user code, without slowing down the compiler with... — committed to golang/go by cuonglm a year ago

Most upvoted comments

there’s a 12000 line / 6000 case switch in there

seankhliao on Jan 23, 2023

This is fixed at tip. Milestoning for 1.20 for the backport.

randall77 on Jan 24, 2023

main » time go1.19.5 build -a               
go1.19.5 build -a  9.57s user 0.79s system 279% cpu 3.702 total

main » gotip version         
go version devel go1.21-e2fe35363d0 Mon Jan 23 10:02:20 2023 +0000 linux/amd64

main » time gotip build -a
gotip build -a  3983.07s user 58.04s system 771% cpu 8:43.65 total

seankhliao on Jan 23, 2023