GCC 4.6.x miscompiling arm-linux?
Mikael Pettersson
mikpe at it.uu.se
Tue Sep 11 10:10:14 EDT 2012
David Jander writes:
> On Tue, 11 Sep 2012 14:53:35 +0200
> Mikael Pettersson <mikpe at it.uu.se> wrote:
>
> > David Jander writes:
> > > On Tue, 11 Sep 2012 13:35:40 +0200
> > > Mikael Pettersson <mikpe at it.uu.se> wrote:
> > >
> > > > David Jander writes:
> > > > > > I can make the patches available if there's confirmation that a vanilla
> > > > > > upstream gcc-4.6.3 doesn't work.
> > > > >
> > > > > I am pretty sure this is the case... do you have a patch series that you can
> > > > > easily tar and mail to me? I'd like to try those patches with OSELAS, to see
> > > > > if I can indeed build a gcc-4.6.3 toolchain that generates correct code.... I
> > > > > already know that I can generate one that doesn't ;-)
> > > > >
> > > > ...
> > > > > > If you're sure no add-on patches were applied, then yes please do.
> > > > >
> > > > > Pretty sure, but not 100%, so I'd like to try your patches first if you don't
> > > > > mind....
> > > >
> > > > And I'd like to confirm first. Please tell us the following:
> > > >
> > > > > > > > 2: include the output of gcc -v which tells how that gcc was configured,
> > >
> > > Using built-in specs.
> > > COLLECT_GCC=/opt/OSELAS.Toolchain-2011.11.1/arm-v5te-linux-gnueabi/gcc-4.6.3-glibc-2.14.1-binutils-2.21.1a-kernel-2.6.39-sanitized/bin/arm-v5te-linux-gnueabi-gcc-4.6.3
> > > COLLECT_LTO_WRAPPER=/opt/OSELAS.Toolchain-2011.11.1/arm-v5te-linux-gnueabi/gcc-4.6.3-glibc-2.14.1-binutils-2.21.1a-kernel-2.6.39-sanitized/libexec/gcc/arm-v5te-linux-gnueabi/4.6.3/lto-wrapper
> > > Target: arm-v5te-linux-gnueabi
> > > Configured with: /home/djander/ptxdist/OSELAS.Toolchain-2011.11.1/platform-arm-v5te-linux-gnueabi-gcc-4.6.3-glibc-2.14.1-binutils-2.21.1a-kernel-2.6.39-sanitized/build-cross/gcc-4.6.3/configure --target=arm-v5te-linux-gnueabi --with-sysroot=/opt/OSELAS.Toolchain-2011.11.1/arm-v5te-linux-gnueabi/gcc-4.6.3
> > > -glibc-2.14.1-binutils-2.21.1a-kernel-2.6.39-sanitized/sysroot-arm-v5te-linux-gnueabi --disable-multilib --with-float=soft --with-fpu=vfp --with-cpu=arm926ej-s --enable-__cxa_atexit --disable-sjlj-exceptions --disable-nls --disable-decimal-float --disable-fixed-point --disable-win32-registry --enable-symvers=gnu --with-pkgversion=OSELAS.Toolchain-2011.11.1 --with-system-zlib --with-gmp=/home/djander/ptxdist/OSELAS.Toolchain-2011.11.1/platform-arm-v5te
> > > -linux-gnueabi-gcc-4.6.3-glibc-2.14.1-binutils-2.21.1a-kernel-2.6.39-sanitized/sysroot-host --with-mpfr=/home/djander/ptxdist/OSELAS.Toolchain-2011.11.1/platform-arm-v5te-linux-gnueabi-gcc-4.6.3-glibc-2.14.1-binutils-2.21.1a-kernel-2.6.39-sanitized/sysroot-host --prefix=/opt/OSELAS.Toolchain-2011.11.1/arm-v5te-linux-gnueabi/gcc-4.6.3-glibc-2.14.1-binutils-2.21.1a-kernel-2.6.39-sanitized --enable-languages=c,c++ --enable-threads=posix --enable-c99 --enable-long-long --enable-libstdcxx-debug --enable-profile --enable-shared --disable-libssp --enable-checking=release
> > > Thread model: posix
> > > gcc version 4.6.3 (OSELAS.Toolchain-2011.11.1)
> > >
> > > > > > > > 3: give the exact set of gcc options used then compiling the test case.
> > >
> > > If I type this in a terminal:
> > >
> > >
> > > $ /opt/OSELAS.Toolchain-2011.11.1/arm-v5te-linux-gnueabi/gcc-4.6.3-glibc-2.14.1-binutils-2.21.1a-kernel-2.6.39-sanitized/bin/arm-v5te-linux-gnueabi-gcc-4.6.3 -Os -S -o - -x c -
> > >
> > > struct flexcan_regs {
> > > unsigned int mcr;
> > > unsigned int rxfgmask;
> > > };
> > >
> > > #define flexcan_read(a) (*(volatile unsigned int *)(a))
> > > #define flexcan_write(v,a) (*(volatile unsigned int *)(a) = (v))
> > >
> > > int flexcan_chip_start(int ver, struct flexcan_regs *regs)
> > > {
> > > flexcan_write(0, ®s->mcr);
> > >
> > > if (ver >= 10)
> > > flexcan_write(0, ®s->rxfgmask);
> > >
> > > return 0;
> > > }
> > >
> > >
> > > I get this output after hitting <CTRL-D>:
> > >
> > > .cpu arm926ej-s
> > > .fpu softvfp
> > > .eabi_attribute 20, 1
> > > .eabi_attribute 21, 1
> > > .eabi_attribute 23, 3
> > > .eabi_attribute 24, 1
> > > .eabi_attribute 25, 1
> > > .eabi_attribute 26, 2
> > > .eabi_attribute 30, 4
> > > .eabi_attribute 18, 4
> > > .file ""
> > > .text
> > > .align 2
> > > .global flexcan_chip_start
> > > .type flexcan_chip_start, %function
> > > flexcan_chip_start:
> > > @ args = 0, pretend = 0, frame = 0
> > > @ frame_needed = 0, uses_anonymous_args = 0
> > > @ link register save eliminated.
> > > mov r3, #0
> > > cmp r0, #9
> > > str r3, [r1, #0]
> > > ldrle r3, [r1, #4]
> > > mov r0, #0
> > > str r3, [r1, #4]
> > > bx lr
> > > .size flexcan_chip_start, .-flexcan_chip_start
> > > .ident "GCC: (OSELAS.Toolchain-2011.11.1) 4.6.3"
> > > .section .note.GNU-stack,"",%progbits
> > >
> > >
> > > Do you need more information?
> >
> > No, I can reproduce the bug with vanilla gcc-4.6.3; vanilla 4.7.1 and 4.5.4 are Ok.
> >
> > I'll bisect my 4.6.3 patch series to see which patch fixes it.
>
> Great. Thanks a lot for your help so far. Looking forward to see what fixes
> this issue. Are you implying that you will also file the bug (and possible
> patch) with gcc.gnu.org, or do you prefer me to do that?
This is a known bug: <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52445>.
It was reported and fixed in gcc trunk on March 1 this year, but missed
the gcc-4.6.3 release made the same day (and frozen a week or so before),
and it hasn't been applied to gcc-4.6.4 branch yet either.
I've been using and testing the fix in my own gcc-4.6 branch since March 4
without regressions. I'm attaching my backport of the fix below.
I'll ping gcc upstream about getting this into gcc-4.6.4.
/Mikael
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