http://sourceware.org/bugzilla/show_bug.cgi?id=15348
Bug #: 15348
Summary: GCC inline assembler for ARM thumb16 mnemonic lsls not
recognized for CPU cortex-m0
Product: binutils
Version: 2.23
Status: NEW
Severity: normal
Priority: P2
Component: gas
AssignedTo: unassig...@sourceware.org
ReportedBy: eleven...@gmail.com
Classification: Unclassified
Feedback from GCC maintainers is that this issue is the responsibility of
binutils.
---
It looks like the inline assembler when -mcpu=cortex=m0 is selected doesn't
recognize the "lsls" mnemonic. It assembles "lsl" and emits the instruction
that the disassembler identifies as "lsls".
The hitch is that this mismatch requires different inline assembler when the
cpu changes between M0 and M3/M4. On M3, the "lsl" instruction will not set
the condition flags.
---
Given a source file:
void test () {
__asm volatile ("lsls r0, #1");
}
For Cortex-M0,
elf@cerise lsl-bug > /opt/gcc/bin/arm-none-eabi-gcc -g -Os -c -mcpu=cortex-m0
-mthumb lsl.c -o lsl.o
/tmp/ccuEyZSU.s: Assembler messages:
/tmp/ccuEyZSU.s:29: Error: instruction not supported in Thumb16 mode -- `lsls
r0,#1'
If the instruction is changed to "lsl r0, #1" the compiler is happy and the
emitted machine code is correct. The disassembler accurately identifies the
instruction as lsls because that's the only form of lsl that the M0 supports.
void test ()
{
__asm volatile ("lsl r0, #1");
0: 0040 lsls r0, r0, #1
}
2: 4770 bx lr
So, I think that the issue is only in the inline assembler in that it doesn't
accept the "lsls" opcode....or is there another explanation?
---
For references:
elf@cerise lsl-bug > /opt/gcc/bin/arm-none-eabi-gcc -v -mcpu=cortex-m0 -mthumb
Using built-in specs.
COLLECT_GCC=/opt/gcc/bin/arm-none-eabi-gcc
COLLECT_LTO_WRAPPER=/opt/gcc/libexec/gcc/arm-none-eabi/4.7.2/lto-wrapper
Target: arm-none-eabi
Configured with: ../gcc-4.7.2/configure --target=arm-none-eabi
--prefix=/opt/gcc --enable-multilib --enable-languages=c,c++ --with-newlib
--with-gnu-as --with-gnu-ld --disable-nls --disable-shared --disable-threads
--with-headers=newlib/libc/include --disable-libssp --disable-libstdcxx-pch
--disable-libmudflap --disable-libgomp --disable-werror --with-system-zlib
--disable-newlib-supplied-syscalls
Thread model: single
gcc version 4.7.2 (GCC)
elf@cerise lsl-bug > /opt/gcc/bin/arm-none-eabi-as --version
GNU assembler (GNU Binutils) 2.23.1
Copyright 2012 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or later.
This program has absolutely no warranty.
This assembler was configured for a target of `arm-none-eabi'.
elf@cerise lsl-bug > /opt/gcc/bin/arm-none-eabi-ld --version
GNU ld (GNU Binutils) 2.23.1
Copyright 2012 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or (at your option) a later version.
This program has absolutely no warranty.
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