[Bug lto/105641] New: Floating point constants are 0 in C LTO objects

["richard at weickelt dot de" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105641

            Bug ID: 105641
           Summary: Floating point constants are 0 in C LTO objects
           Product: gcc
           Version: 10.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
          Assignee: unassigned at gcc dot gnu.org
          Reporter: richard at weickelt dot de
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

When compiling C code with arm-none-eabi-gcc and -flto on a Linux host and
linking the final binary on a Windows host with exactly the same toolchain
version, all float constants are 0, whereas the rest of the code seems valid.
Code compiled with g++ is not affected by this, only gcc.

Example code:


    float test_float()
    {
        return 47.0;
    }


Compilation:

    arm-none-eabi-gcc -Os -flto -c test.c -o test.o

Dumping GIMPLE code on the same Linux host shows:


    arm-none-eabi-lto-dump -dump-body=test_float test.o

    test_float ()
    {
      <bb 2> [local count: 1073741824]:
      return 4.7e+1;
    }


Dumping GIMPLE code on a Windows host with the same toolchain release:

    arm-none-eabi-lto-dump.exe -dump-body=test_float test.o

    test_float ()
    {
      <bb 2> [local count: 1073741824]:
      return 0.0e+0;
    }

The GIMPLE code matches what I observe in the final binary. I expect LTO
objects to be compatible across different host operating systems as long as the
toolchain version matches. The fact that it works just fine with g++ and/or
integer values, indicates a bug somewhere in the toolchain.

GCC configuration on Linux:

   
/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/src/gcc/configure
--target=arm-none-eabi
--prefix=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-native
--libexecdir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-native/lib
--infodir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-native/share/doc/gcc-arm-none-eabi/info
--mandir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-native/share/doc/gcc-arm-none-eabi/man
--htmldir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-native/share/doc/gcc-arm-none-eabi/html
--pdfdir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-native/share/doc/gcc-arm-none-eabi/pdf
--enable-languages=c,c++ --enable-plugins --disable-decimal-float
--disable-libffi --disable-libgomp --disable-libmudflap --disable-libquadmath
--disable-libssp --disable-libstdcxx-pch --disable-nls --disable-shared
--disable-threads --disable-tls --with-gnu-as --with-gnu-ld --with-newlib
--with-headers=yes --with-python-dir=share/gcc-arm-none-eabi
--with-sysroot=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-native/arm-none-eabi
--build=x86_64-linux-gnu --host=x86_64-linux-gnu
--with-gmp=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/build-native/host-libs/usr
--with-mpfr=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/build-native/host-libs/usr
--with-mpc=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/build-native/host-libs/usr
--with-isl=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/build-native/host-libs/usr
--with-libelf=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/build-native/host-libs/usr
--with-host-libstdcxx='-static-libgcc -Wl,-Bstatic,-lstdc++,-Bdynamic -lm'
--with-pkgversion='GNU Arm Embedded Toolchain 10.3-2021.10'
--with-multilib-list=rmprofile,aprofile
Thread model: single
Supported LTO compression algorithms: zlib

Configuration on Windows:

/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-260_20210727_1627371386/src/gcc/configure
--build=x8
6_64-linux-gnu --host=i686-w64-mingw32 --target=arm-none-eabi
--prefix=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipelin
e-260_20210727_1627371386/install-mingw
--libexecdir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-260_20210727_162
7371386/install-mingw/lib
--infodir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-260_20210727_1627371386/install-m
ingw/share/doc/gcc-arm-none-eabi/info
--mandir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-260_20210727_162737138
6/install-mingw/share/doc/gcc-arm-none-eabi/man
--htmldir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-260_2021072
7_1627371386/install-mingw/share/doc/gcc-arm-none-eabi/html
--pdfdir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-
260_20210727_1627371386/install-mingw/share/doc/gcc-arm-none-eabi/pdf
--enable-languages=c,c++ --enable-mingw-wildcard --disable-decim
al-float --disable-libffi --disable-libgomp --disable-libmudflap
--disable-libquadmath --disable-libssp --disable-libstdcxx-pch --disa
ble-nls --disable-shared --disable-threads --disable-tls --with-gnu-as
--with-gnu-ld --with-headers=yes --with-newlib --with-python-di
r=share/gcc-arm-none-eabi
--with-sysroot=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-260_20210727_1627371386/inst
all-mingw/arm-none-eabi
--with-libiconv-prefix=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-260_20210727_162737138
6/build-mingw/host-libs/usr
--with-gmp=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-260_20210727_1627371386/build-
mingw/host-libs/usr
--with-mpfr=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-260_20210727_1627371386/build-mingw/h
ost-libs/usr
--with-mpc=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-260_20210727_1627371386/build-mingw/host-libs
/usr
--with-isl=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-260_20210727_1627371386/build-mingw/host-libs/usr
--w
ith-libelf=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-260_20210727_1627371386/build-mingw/host-libs/usr
--with-h
ost-libstdcxx='-static-libgcc -Wl,-Bstatic,-lstdc++,-Bdynamic -lm'
--with-pkgversion='GNU Arm Embedded Toolchain 10.3-2021.07' --with-
multilib-list=rmprofile,aprofile
Thread model: single
Supported LTO compression algorithms: zlib

GCC version 10.3.1 20210621