http://sourceware.org/bugzilla/show_bug.cgi?id=12793
Summary: arm: push/pop equivalents using stm/ldm mnemonics
assembled inconsistently
Product: binutils
Version: 2.22 (HEAD)
Status: NEW
Severity: normal
Priority: P2
Component: gas
AssignedTo: unassig...@sources.redhat.com
ReportedBy: dave.mar...@linaro.org
Observed on trunk, 2011-05-17
Configured with --{build,host}=x86_64-pc-linux-gnu --target=arm-elf-eabi
$ cat <<EOF >stm-ldm.s
.syntax unified
.thumb
.type f, %function
.globl f
f:
push {r0}
stmfd sp!, {r0}
@ stmfd.n sp!, {r0}
push {r0-r1}
stmfd sp!, {r0-r1}
@ stmfd.n sp!, {r0-r1}
push {r0,lr}
stmfd sp!, {r0,lr}
ldmfd sp!, {r0,lr}
@ ldmfd.n sp!, {r0,lr}
pop {r0,pc}
ldmfd sp!, {r0-r1}
ldmfd.n sp!, {r0-r1}
ldmfd sp!, {r0}
ldmfd.n sp!, {r0}
pop {r0}
EOF
# The commented-out lines above generate "cannot honor width suffix" errors if
assembled.
# All of the above ldmfd/stmfd instructions are equivalent to the adjacent
push/pop mnemonics, and could be assembled to 16-bit encodings.
$ as -march=armv7-a -o stm-ldm.o stm-ldm.s
$ objdump -d stm-ldm.o
stm-ldm.o: file format elf32-littlearm
Disassembly of section .text:
00000000 <f>:
0: b401 push {r0}
2: f84d 0d04 str.w r0, [sp, #-4]!
6: b403 push {r0, r1}
8: e92d 0003 stmdb sp!, {r0, r1}
c: b501 push {r0, lr}
e: e92d 4001 stmdb sp!, {r0, lr}
12: e8bd 4001 ldmia.w sp!, {r0, lr}
16: bd01 pop {r0, pc}
18: bc03 pop {r0, r1}
1a: bc03 pop {r0, r1}
1c: bc01 pop {r0}
1e: bc01 pop {r0}
20: bc01 pop {r0}
It looks rather like the older ARM logic may be being used to choose encodings
when using the ldm/stm mnemonics in Thumb, in some cases.
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