Repository navigation
cmd/asm: amd64 assembler loops forever on a forward jump to a labelled PCALIGN when a branch needs widening [1.27 backport] #81927
Description
@lizthegrey requested issue #81792 to be considered for backport to the next 1.27 minor release.
@gopherbot please backport to Go 1.26 and Go 1.27
This is a regression introduced in Go 1.26 by CL 696915 (the #74648 fix). Every 1.26.x and 1.27.x release is affected.
The failure is a silent hang:
go buildnever finishes and prints no error, so the cause is hard to find. The only workaround is to move the label in the assembly source.This was hit in real generated code (github.com/klauspost/compress), which now works around it.
The fix, go.dev/cl/839925, is a one-line change in
span6with a regression test.
Activity
gopherbot commentedon Sep 30, 2026
Change https://go.dev/cl/842345 mentions this issue:
[release-branch.go1.27] cmd/internal/obj/x86: clear forward-jump list on PCALIGNdmitshur commentedon Oct 6, 2026
We discussed this in a release meeting. Approved the already-created backport CL.