https://sourceware.org/bugzilla/show_bug.cgi?id=24571
Bug ID: 24571
Summary: [avr] Relaxation does not shorten jmp or call to
target at pc-relative range boundary
Product: binutils
Version: 2.31
Status: NEW
Severity: normal
Priority: P2
Component: ld
Assignee: unassigned at sourceware dot org
Reporter: saaadhu at gcc dot gnu.org
Target Milestone: ---
For the following piece of code, linker relaxation does not transform the jmp
to forward_target into an rjmp, even though the target label is within range of
a pc-relative jump.
$ cat relax-insn-at-range-boundary.s
.section ".text", "ax",@progbits
.global main
main:
backward_target: ; Exactly -4094 bytes from jmp
.ds.b 4094, 0
jmp backward_target
jmp forward_target
.ds.b 4094, 0
forward_target: ; Exactly 4098 bytes before relax, 4096 bytes
after relax
nop
$ avr-as -m avr51 relax-insn-at-range-boundary.s -o tmp.o
$ avr-ld -m avr51 --relax tmp.o
$ avr-objdump -d a.out
a.out: file format elf32-avr
Disassembly of section .text:
00000000 <__ctors_end>:
...
ffc: 00 00 nop
ffe: 00 c8 rjmp .-4096 ; 0x0 <__ctors_end>
1000: 0c 94 01 10 jmp 0x2002 ; 0x2002 <forward_target>
...
00002002 <forward_target>:
...
The forward_target label is at a distance of 4098 bytes - if the jmp is relaxed
to rjmp, the distance gets reduced to 4096, and with the implicit PC increment
of 2, that address is reachable via rjmp .+4094
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