This bug is seen on arm-*-eabi when generating thumb2 instructions with
interrupt functions that store variables on the stack. I've reduced the problem
to the following simple test case:
void function(int * x);
void interrupt_handler() __attribute__((__interrupt__));
void interrupt_handler()
{
int data;
function(&data);
}
The undefined function is just the simplest way I could think of to prevent the
compiler from optimizing away the data variable or converting it to a register.
The above code is compiled with:
arm-none-eabi-gcc -mcpu=cortex-m3 -mthumb -Os -c -o bug.o bug.c
Which generates the assembly for interrupt_handler:
mov r0, sp
bic.w r1, r0, #7 ; 0x7
mov sp, r1
push {r0, lr}
sub sp, #8
add r0, sp, #4
bl 0 <function>
ldmia.w sp!, {r0, r2, r3, lr}
mov sp, r0
bx lr
The problem is the last ldmia instruction which incorrectly pops off the values
from the stack.
When compiling with any other optimization flags besides -Os (-O0, -O1, -O2 or
-O3) the problem does not occur.
I see this bug in the gcc snapshot version 4.4.0-20090313 with the following
configure options:
../../../src/gcc-4.4-20090313/configure
--prefix=/usr/local/arm-none-eabi
--target=arm-none-eabi --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --enable-interwork --enable-languages=c,c++
--with-newlib --without-headers --disable-shared --with-gnu-as
--with-gnu-ld --disable-newlib-supplied-syscalls --disable-libgloss
--disable-libssp --disable-libmudflap --disable-libssp
--disable-libgomp --disable-libstdcxx-pch --disable-nls
--with-gmp=/home/logang/Projects/toolchain/x86_64-linux-gnu/arm-none-eabi/gcc/../../support
--with-mpfr=/home/logang/Projects/toolchain/x86_64-linux-gnu/arm-none-eabi/gcc/../../support
'CFLAGS_FOR_TARGET=-ffunction-sections -Os -fdata-sections
-fomit-frame-pointer -D__BUFSIZ__=256 -DPREFER_SIZE_OVER_SPEED
-D__OPTIMIZE_SIZE__'
This bug does not occur in gcc 4.3.3 with everything else the same.
Thanks,
Logan
--
Summary: GCC Generates Incorrect Stack Instructins for Interrupts
When using -Os
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: logang at ece dot ualberta dot ca
GCC build triplet: x86_64-linux-gnu
GCC host triplet: x86_64-linux-gnu
GCC target triplet: arm-*-eabi
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39585
