https://sourceware.org/bugzilla/show_bug.cgi?id=25848
Bug ID: 25848
Summary: cmpi to local label produces wrong code on 68000
Product: binutils
Version: unspecified
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: gas
Assignee: unassigned at sourceware dot org
Reporter: vincent.riviere at freesbee dot fr
Target Milestone: ---
Target: m68k-elf
Tested with gas 2.34.50.20200418 freshly compiled fom Git.
Basically, cmpi to local label is optimized by gas to PC-relative label. But
this addressing mode is actually only supported on 68020+.
$ cat bug.s
lab:
cmpi.w #1,lab
$ m68k-elf-as -m68000 bug.s -o bug.o && m68k-elf-objdump -d bug.o
bug.o: file format elf32-m68k
Disassembly of section .text:
00000000 <lab>:
0: 0c7a 0001 fffc cmpiw #1,%pc@(0 <lab>)
We have specifically asked for 68000 compilation. We can see that the reference
to the absolute "lab" label has been silently replaced by a PC-relative label.
But on plain 68000, that addressing mode is unsupported. See M68000PRM.pdf,
instruction CMPI "Compare Immediate".
gas should not blindly convert absolute to PC-relative addressing with cmpi
when compiling for 68000.
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