Bug#735310: Error: bad register name `%bpl' in i386

[Alberto Garcia <berto@igalia.com>]

Package: gcc-4.8
Version: 4.8.2-12
Severity: important

webkitgtk 2.3.4 FTBFS with the latest gcc-4.8:

../Source/WTF/wtf/Atomics.h: Assembler messages:
../Source/WTF/wtf/Atomics.h:300: Error: bad register name `%sil'
[...]

You can see the full log here:

   https://buildd.debian.org/status/fetch.php?pkg=webkitgtk&arch=i386&ver=2.3.4-1&stamp=1389693794

My understanding is that gcc is incorrectly producing x86-64 registers
when generating x86 code.

I managed to narrow it down with a pre-processed version of the
CodeBlock.cpp source file from webkit (I can attach it or post it
somewhere, it's ~400KB of compressed code):

$ gcc -O1 -m32 --std=c++11 -c CodeBlock.ii 
../Source/WTF/wtf/Atomics.h: Assembler messages:
../Source/WTF/wtf/Atomics.h:300: Error: bad register name `%bpl'
../Source/WTF/wtf/Atomics.h:300: Error: bad register name `%bpl'
../Source/WTF/wtf/Atomics.h:300: Error: bad register name `%dil'

This works fine, though (which I don't quite understand since
-frename-registers should already be enabled by -O1):

$ gcc -O1 -m32 --std=c++11 -c -frename-registers CodeBlock.ii 

Here's the relevant part of the source file:

inline bool weakCompareAndSwap(uint8_t* location, uint8_t expected, uint8_t newValue)
{
    unsigned char result;
    asm volatile(
        "lock; cmpxchgb %3, %2\n\t"
        "sete %1"
        : "+a"(expected), "=q"(result), "+m"(*location)
        : "r"(newValue)
        : "memory"
        );
    return result;
}

This upstream GCC bug is related:

   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=10153

Although the suggestion to use '=r' instead of '=q' doesn't seem to
solve the problem.

Berto

-- System Information:
Debian Release: jessie/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 3.12-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages gcc-4.8 depends on:
ii  binutils        2.24-2
ii  cpp-4.8         4.8.2-12
ii  gcc-4.8-base    4.8.2-12
ii  libc6           2.17-97
ii  libcloog-isl4   0.18.1-3
ii  libgcc-4.8-dev  4.8.2-12
ii  libgmp10        2:5.1.3+dfsg-1
ii  libisl10        0.12.1-2
ii  libmpc3         1.0.1-1
ii  libmpfr4        3.1.2-1
ii  zlib1g          1:1.2.8.dfsg-1

Versions of packages gcc-4.8 recommends:
ii  libc6-dev  2.17-97

Versions of packages gcc-4.8 suggests:
ii  binutils [binutils-gold]  2.24-2
ii  gcc-4.8-doc               4.8.2-2
pn  gcc-4.8-locales           <none>
pn  gcc-4.8-multilib          <none>
pn  libasan0-dbg              <none>
pn  libatomic1-dbg            <none>
pn  libbacktrace1-dbg         <none>
pn  libgcc1-dbg               <none>
pn  libgomp1-dbg              <none>
pn  libitm1-dbg               <none>
pn  libquadmath0-dbg          <none>
pn  libtsan0-dbg              <none>

-- no debconf information