lld incorrectly calculates the maximum range of R_HEX_B22_PCREL relocation

[androm3da]

When building the linux kernel, we see the following link error:

ld.lld: error: vmlinux.a(arch/hexagon/kernel/head.o):(.init.text+0x160):
relocation R_HEX_B22_PCREL out of range: 2098032 is not in [-2097152, 2097151]; references 'memset'

This issue was triggered by changes in layout but it uncovered an error in the way lld calculates the range of this relocation.

See also https://lore.kernel.org/linux-hexagon/20241114171834.GA1956005@thelio-3990X

[llvmbot]

@llvm/issue-subscribers-lld-elf

Author: Brian Cain (androm3da)

When building the linux kernel, we see the following link error:

ld.lld: error: vmlinux.a(arch/hexagon/kernel/head.o):(.init.text+0x160):
relocation R_HEX_B22_PCREL out of range: 2098032 is not in [-2097152, 2097151]; references 'memset'

This issue was triggered by changes in layout but it uncovered an error in the way lld calculates the range of this relocation.

See also https://lore.kernel.org/linux-hexagon/20241114171834.GA1956005@thelio-3990X

[llvmbot]

@llvm/issue-subscribers-backend-hexagon

Author: Brian Cain (androm3da)

When building the linux kernel, we see the following link error:

ld.lld: error: vmlinux.a(arch/hexagon/kernel/head.o):(.init.text+0x160):
relocation R_HEX_B22_PCREL out of range: 2098032 is not in [-2097152, 2097151]; references 'memset'

This issue was triggered by changes in layout but it uncovered an error in the way lld calculates the range of this relocation.

See also https://lore.kernel.org/linux-hexagon/20241114171834.GA1956005@thelio-3990X

[androm3da]

This is fixed by #115925 - so we can cherry-pick it once it lands.

[androm3da]

/cherry-pick 64e3466

[llvmbot]

Failed to cherry-pick: 64e3466

https://github.com/llvm/llvm-project/actions/runs/11916300231

Please manually backport the fix and push it to your github fork. Once this is done, please create a pull request

[alexrp]

@androm3da does this look like the same issue?

...snip...
error: ld.lld: /home/alexrp/Source/ziglang/zig/.zig-cache/o/ac233994cecab126ab11a1a886c69fbb/test.o:(function debug.panicExtra__anon_2192: .text+0x1c7c): relocation R_HEX_B22_PCREL out of range: 2107140 is not in [-2097152, 2097151]; references 'memset'
    note: referenced by debug.zig:440 (/home/alexrp/Source/ziglang/zig/lib/std/debug.zig:440)
    note: defined in /home/alexrp/.cache/zig/o/019c1e69a1297cefadacb81f30c8d941/libcompiler_rt.a(/home/alexrp/.cache/zig/o/019c1e69a1297cefadacb81f30c8d941/libcompiler_rt.a.o)
...snip...
error: ld.lld: /home/alexrp/Source/ziglang/zig/.zig-cache/o/ac233994cecab126ab11a1a886c69fbb/test.o:(function fifo.LinearFifo(u8,.{ .Dynamic = {} }).realign: .text+0x4288): relocation R_HEX_B22_PCREL out of range: 2097208 is not in [-2097152, 2097151]; references 'memcpy'
    note: referenced by fifo.zig:99 (/home/alexrp/Source/ziglang/zig/lib/std/fifo.zig:99)
    note: defined in /home/alexrp/.cache/zig/o/019c1e69a1297cefadacb81f30c8d941/libcompiler_rt.a(/home/alexrp/.cache/zig/o/019c1e69a1297cefadacb81f30c8d941/libcompiler_rt.a.o)
...snip...

I get a bunch of relocation errors of this sort when linking Zig's compiler-rt tests.

[androm3da]

@androm3da does this look like the same issue?

Yes it does. Note that even after this is fixed there's a (small) chance for relocations to be too far apart (if the call site is not extended and the executable is fairly large). But: #111217 should address that when it lands.

[androm3da]

This has been fixed in release/19.x and main branches.

[alexrp]

@androm3da building Zig's std tests (fairly large binary at 69M), we now get lots of:

error: ld.lld: /home/alexrp/Source/ziglang/zig/.zig-cache/o/ef6d73811ed43e51b7ff5085bd10310c/test.o:(function os.linux.test.test.user and group ids: .text+0x138d57c): relocation R_HEX_B22_PCREL out of range: -11927916 is not in [-8388608, 8388607]; references 'getauxval'
    note: referenced by test.zig:107 (/home/alexrp/Source/ziglang/zig/lib/std/os/linux/test.zig:107)
    note: defined in /home/alexrp/Source/ziglang/zig/.zig-cache/o/ef6d73811ed43e51b7ff5085bd10310c/test.o
error: ld.lld: /home/alexrp/Source/ziglang/zig/.zig-cache/o/ef6d73811ed43e51b7ff5085bd10310c/test.o:(function os.linux.test.test.user and group ids: .text+0x138d5ec): relocation R_HEX_B22_PCREL out of range: -11928028 is not in [-8388608, 8388607]; references 'getauxval'
    note: referenced by test.zig:108 (/home/alexrp/Source/ziglang/zig/lib/std/os/linux/test.zig:108)
    note: defined in /home/alexrp/Source/ziglang/zig/.zig-cache/o/ef6d73811ed43e51b7ff5085bd10310c/test.o
error: ld.lld: /home/alexrp/Source/ziglang/zig/.zig-cache/o/ef6d73811ed43e51b7ff5085bd10310c/test.o:(function os.linux.test.test.user and group ids: .text+0x138d65c): relocation R_HEX_B22_PCREL out of range: -11928140 is not in [-8388608, 8388607]; references 'getauxval'
    note: referenced by test.zig:109 (/home/alexrp/Source/ziglang/zig/lib/std/os/linux/test.zig:109)
    note: defined in /home/alexrp/Source/ziglang/zig/.zig-cache/o/ef6d73811ed43e51b7ff5085bd10310c/test.o
error: ld.lld: /home/alexrp/Source/ziglang/zig/.zig-cache/o/ef6d73811ed43e51b7ff5085bd10310c/test.o:(function os.linux.test.test.user and group ids: .text+0x138d6cc): relocation R_HEX_B22_PCREL out of range: -11928252 is not in [-8388608, 8388607]; references 'getauxval'
    note: referenced by test.zig:110 (/home/alexrp/Source/ziglang/zig/lib/std/os/linux/test.zig:110)
    note: defined in /home/alexrp/Source/ziglang/zig/.zig-cache/o/ef6d73811ed43e51b7ff5085bd10310c/test.o

I'm wondering if we might be hitting this bug again, or if we're just running into an actual toolchain limitation here.

[androm3da]

@androm3da building Zig's std tests (fairly large binary at 69M), we now get lots of:
...
I'm wondering if we might be hitting this bug again, or if we're just running into an actual toolchain limitation here.

It's the latter. I have not gotten around to finishing the remaining work for #111217, sadly. Hopefully we can resurrect that one and polish off the remaining work.