GCC g++ ICE on i586

hmm I forgot to mention that if I revert r99474 then the ICE goes away. I can not reproduce this issue with upstream gcc trunk

Confirmed in gcc-linaro-4.5+bzr99476. Appears at -Os on 32 bit only - x86_64 is fine, -O1 is fine, -O2 is fine.

Hits an assertion at the end of dwarf2out_begin_epilogue:

  /* And emulate the state save. */
  gcc_assert (!cfa_remember.in_use);
  cfa_remember = cfa;
  cfa_remember.in_use = 1;
}

Set to low priority as it's size only in a non-code generation area.

This bug is still present in the 2011.03-0 milestone build. It breaks the build of eglibc's libstdc++ (and therefore the construction of a cross toolchain) at -mcpu=pentium-m -Os, which is the tuning we've been using for our embedded device.

Adding -fomit-frame-pointer makes the ICE disappear:

build@ctbu-bld5:~$ /home/build/x-tools-x86/targets/i686-cm-linux-gnu/build/build-cc/./gcc/xgcc -shared-libgcc -B/home/build/x-tools-x86/targets/i686-cm-linux-gnu/build/build-cc/./gcc -nostdinc++ -L/home/build/x-tools-x86/targets/i686-cm-linux-gnu/build/build-cc/i686-cm-linux-gnu/libstdc++-v3/src -L/home/build/x-tools-x86/targets/i686-cm-linux-gnu/build/build-cc/i686-cm-linux-gnu/libstdc++-v3/src/.libs -B/opt/x-tools/i686-cm-linux-gnu/i686-cm-linux-gnu/bin/ -B/opt/x-tools/i686-cm-linux-gnu/i686-cm-linux-gnu/lib/ -isystem /opt/x-tools/i686-cm-linux-gnu/i686-cm-linux-gnu/include -isystem /opt/x-tools/i686-cm-linux-gnu/i686-cm-linux-gnu/sys-include -I/home/build/x-tools-x86/targets/i686-cm-linux-gnu/build/build-cc/i686-cm-linux-gnu/libstdc++-v3/include/i686-cm-linux-gnu -I/home/build/x-tools-x86/targets/i686-cm-linux-gnu/build/build-cc/i686-cm-linux-gnu/libstdc++-v3/include -I/home/build/x-tools-x86/targets/src/gcc-linaro-4.5-2011.03-0/libstdc++-v3/libsupc++ -fno-implicit-templates -Wall -Wextra -Wwrite-strings -Wcast-qual -fdiagnostics-show-location=once -ffunction-sections -fdata-sections -g -Os -c /home/build/x-tools-x86/targets/src/gcc-linaro-4.5-2011.03-0/libstdc++-v3/src/ios_init.cc -o ios_init.o -fomit-frame-pointer

build@ctbu-bld5:~$ /home/build/x-tools-x86/targets/i686-cm-linux-gnu/build/build-cc/./gcc/xgcc -shared-libgcc -B/home/build/x-tools-x86/targets/i686-cm-linux-gnu/build/build-cc/./gcc -nostdinc++ -L/home/build/x-tools-x86/targets/i686-cm-linux-gnu/build/build-cc/i686-cm-linux-gnu/libstdc++-v3/src -L/home/build/x-tools-x86/targets/i686-cm-linux-gnu/build/build-cc/i686-cm-linux-gnu/libstdc++-v3/src/.libs -B/opt/x-tools/i686-cm-linux-gnu/i686-cm-linux-gnu/bin/ -B/opt/x-tools/i686-cm-linux-gnu/i686-cm-linux-gnu/lib/ -isystem /opt/x-tools/i686-cm-linux-gnu/i686-cm-linux-gnu/include -isystem /opt/x-tools/i686-cm-linux-gnu/i686-cm-linux-gnu/sys-include -I/home/build/x-tools-x86/targets/i686-cm-linux-gnu/build/build-cc/i686-cm-linux-gnu/libstdc++-v3/include/i686-cm-linux-gnu -I/home/build/x-tools-x86/targets/i686-cm-linux-gnu/build/build-cc/i686-cm-linux-gnu/libstdc++-v3/include -I/home/build/x-tools-x86/targets/src/gcc-linaro-4.5-2011.03-0/libstdc++-v3/libsupc++ -fno-implicit-templates -Wall -Wextra -Wwrite-strings -Wcast-qual -fdiagnostics-show-location=once -ffunction-sections -fdata-sections -g -Os -c /home/build/x-tools-x86/targets/src/gcc-linaro-4.5-2011.03-0/libstdc++-v3/src/ios_init.cc -o ios_init.o -fno-omit-frame-pointer
/home/build/x-tools-x86/targets/src/gcc-linaro-4.5-2011.03-0/libstdc++-v3/src/ios_init.cc: In destructor 'std::ios_base::Init::~Init()':
/home/build/x-tools-x86/targets/src/gcc-linaro-4.5-2011.03-0/libstdc++-v3/src/ios_init.cc:144:3: internal compiler error: in dwarf2out_begin_epilogue, at dwarf2out.c:2859
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for...

I of course did not mean eglibc's libsdc++; I mean Linaro gcc's. (I was *very* tired when I wrote that.) In case it matters, the failure occurred during the "final" compiler phase (after libc installation) of a toolchain build done with crosstool-ng, using an eglibc patched similarly to current Natty.

Note that adding '-fno-shrink-wrap' works around the problem.

LP: #730860 is related.

The patch attached to https://bugs.launchpad.net/ubuntu/+source/gcc-4.5/+bug/730860 fixed the FTBFS. I'll test the resulting system image and report back.

I've just committed a patch from Bernd Schmidt. This issue should now be fixed.

Related: lp:gcc-linaro/4.5,revno=99486

Bernd has now posted this upstream:

http://<email address hidden>/msg01345.html

This is fixed in more recent builds. Tested using:

michaelh@crucis:/mnt/michaelh/linaro/bugs/shrinkwrap$ ~/linaro/toolchains/gcc-linaro-4.5+bzr99502~ams-codesourcery~cs-merge-20110413-x86_64-maverick-cbuild109-crucis-x86_64r1/bin/g++ -m32 -Os -march=pentium -c ios_init.i

on x86_64.