Sometimes the %sil/%dil AMD64 registers are allocated for inline assembler. The
smallest reproducible test case I found is the following code:
int test()
{
register unsigned char a = 1, b = 2, c = 3, d = 4, e = 5, f = 6;
__asm__ __volatile__ (
"movb %0, %1\n"
"movb %2, %3\n"
"movb %4, %5\n" : :
"r" (a), "r" (b), "r" (c), "r" (d),
"r" (e), "r" (f) );
}
int main()
{
test();
}
which correctly reports compilation error when no -O level is specified, but
when -O1, -O2 or -O3 is used (eg. "gcc -O2 -c test.c") the %sil, %dil registers
are incorrectly allocated and the assembling of the object fails.
Tested with
Reading specs from d:/mingw/bin/../lib/gcc/mingw32/3.4.1/specs
Configured with: ../gcc/configure --with-gcc --with-gnu-ld --with-gnu-as
--host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls
--enable-languages=c,c++,f77,ada,objc,java --disable-win32-registry
--disable-shared --enable-sjlj-exceptions --enable-libgcj --disable-java-awt
--without-x --enable-java-gc=boehm --disable-libgcj-debug --enable-interpreter
--enable-hash-synchronization --enable-libstdcxx-debug
Thread model: win32
gcc version 3.4.1 (mingw special)
Reading specs from E:/DIFFs/gcc/bin/../lib/gcc-lib/mingw32/3.3.1/specs
Configured with: ../gcc/configure --with-gcc --with-gnu-ld --with-gnu-as
--host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls
--enable-languages=c,c++,f77,objc,ada,java --disable-win32-registry
--disable-shared --enable-sjlj-exceptions --enable-libgcj --disable-java-awt
--without-x --enable-java-gc=boehm --disable-libgcj-debug --enable-interpreter
--enable-hash-synchronization
Thread model: win32
gcc version 3.3.1 (mingw special 20030804-1)
--
Summary: Invalid register allocation (%sil, %dil)
Product: gcc
Version: 3.4.1
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: inline-asm
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: xnavara at volny dot cz
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: i686-pc-mingw32
GCC host triplet: i686-pc-mingw32
GCC target triplet: i686-pc-mingw32
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19979
