http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60754
Bug ID: 60754
Summary: Missed optimization with inline asm longer than 3
lines
Product: gcc
Version: 4.8.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: rabin at rab dot in
Created attachment 32538
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32538&action=edit
Testcase
At -O2 GCC does not optimize out the call to fail() in the following program if
the asm has four lines.
$ cat testcase.c
extern void fail(void) __attribute__((error("fail")));
static void function(int magic)
{
if (magic > 1)
fail();
__asm__(
"// comment\n"
"// comment\n"
"// comment\n"
#ifndef THREELINEASM
"// comment\n"
#endif
::);
}
void another(void)
{
function(0);
function(1);
}
void dummy(void)
{
another();
}
$ gcc -c -O2 testcase.c
testcase.c: In function ‘function’:
testcase.c:6:8: error: call to ‘fail’ declared with attribute error: fail
fail();
^
$ gcc -c -O2 -DTHREELINEASM testcase.c
$ gcc -c -Os testcase.c
$ gcc -c -O3 testcase.c
$ gcc -v
Using built-in specs.
COLLECT_GCC=/usr/bin/gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.8/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.8.2-16'
--with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.8 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-libmudflap
--enable-plugin --with-system-zlib --disable-browser-plugin
--enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --with-arch-32=i586 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --with-tune=generic --enable-checking=release
--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.8.2 (Debian 4.8.2-16)
