https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101064
Bug ID: 101064
Summary: long compile time in var_tracking for Go package
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: thanm at google dot com
Target Milestone: ---
Created attachment 51008
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51008&action=edit
testcase to reproduce (Go files, some profile reports)
Building the attached Go package with gccgo results in a very long compile
time, apparently due to var_tracking. To reproduce, unpack the tar file and
build with either:
A) go clean -cache; go build .
or
B) gccgo -c -O2 -g -m64 -fgo-pkgpath=xyz ./aenum.go ./avx_optabs.go
[Note: this issue is first posted on the main Go issue tracker at
https://github.com/golang/go/issues/46600; more details there].
This is a fairly modest sized Go package; building it with the main (non-gcc)
Go compiler takes about a third of a second (user + sys, reported by
/bin/time).
For gccgo, building with -O0 takes about a second, but the time taken at -O1
and -O2 are much longer:
-O1: 450 seconds
-O2: 257 seconds
Along with the test case, I am attaching some profiles collected using 'pprof'.
The pass consuming the extra compile time appears to be variable_tracking; from
the profiles the problem looks to be related to alias analysis / memory
disambiguation.
