https://sourceware.org/bugzilla/show_bug.cgi?id=34220
Bug ID: 34220
Summary: [RISC-V] GNU ld.bfd missing second pass relax to
compressed jumps
Product: binutils
Version: 2.45
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: ld
Assignee: unassigned at sourceware dot org
Reporter: l784896635 at gmail dot com
Target Milestone: ---
I ran into this while reducing a RISC-V linker testcase. The reproducer is
already quite small, and I have been seeing the same result consistently across
three reruns.
Summary
=======
GNU ld.bfd stops after the first relaxation pass and leaves the critical site
as 32-bit jal zero / jal ra, while ld.lld reaches the 16-bit c.j / c.jal form
on the same legal inputs.
Expected behavior
=================
A series of call/jump sites become shorter after ordinary relaxation, making a
later critical site eligible for a second relaxation from jal/j to c.jal/c.j.
The linker should continue until the compressed form is reached.
Environment
===========
- product: binutils
- component: ld
- toolchain route: gas+ld.bfd with gas+ld.lld control
- march: rv64ic for j-to-cj and rv32ic for jal-to-cjal
- mabi: lp64/ilp32
- first failing stage: link
Reduced testcase
================
--- j-to-cj.s ---
.text
.globl _start
_start:
tail f1
tail f2
tail f3
tail f4
tail f5
tail f6
tail f7
tail f8
tail f9
tail f10
critical:
tail target
.option norvc
.rept 505
nop
.endr
.option rvc
f1: ret
f2: ret
f3: ret
f4: ret
f5: ret
f6: ret
f7: ret
f8: ret
f9: ret
f10: ret
target:
ret
--- jal-to-cjal.s ---
.text
.globl _start
_start:
call f1
call f2
call f3
call f4
call f5
call f6
call f7
call f8
call f9
call f10
critical:
call target
.option norvc
.rept 505
nop
.endr
.option rvc
f1: ret
f2: ret
f3: ret
f4: ret
f5: ret
f6: ret
f7: ret
f8: ret
f9: ret
f10: ret
target:
ret
Reproduction notes
==================
- This packaged root does not have a single canonical `run.ps1` wrapper.
- Use the reduced inputs under `case/` and follow the commands documented in
`case/README.md`.
- Stable witness outputs, when present, are preserved under
`verify/run1..run3/`.
What I checked
==============
- Reduced inputs are preserved under case/.
- Stable witness outputs are preserved under verify/run1..run3/.
- The strict recheck says stable normalized run signatures across three runs:
True.
- Tracker guidance link:
https://sourceware.org/binutils/docs/ld/Bug-Reporting.html
- evidence summary: 3 clean reproductions under
hunt/verify/bfd_second_pass_compressed_relax/run1..run3 show stable bfd 32-bit
critical jumps in both the j-to-cj and jal-to-cjal tests, while lld compresses
the matching critical sites.
Notes
=====
https://sourceware.org/pipermail/binutils/2026-January/147293.html
Root key: bfd.riscv.missing_second_pass_relax_to_compressed_jumps
Case id: 20260525-bfd-second-pass-compressed-relax
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