| Summary: | optimization bug: unsigned bitfield expands with non-zero padding bits | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Ivanov Pavel <xk-corpse> |
| Component: | target | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | RESOLVED DUPLICATE | ||
| Severity: | normal | CC: | aoliva, aph, bergner, fang, gcc-bugs, ismail, janis, jason, mark, pinskia, rguenth, tromey, xk-corpse |
| Priority: | P3 | Keywords: | wrong-code |
| Version: | 4.2.1 | ||
| Target Milestone: | --- | ||
| Host: | i686-pc-linux-gnu | Target: | powerpc-603-linux-gnu |
| Build: | i686-pc-linux-gnu | Known to work: | |
| Known to fail: | Last reconfirmed: | ||
i'm sorry, i forgot to say that bug appears with any optimization level enabled (-O1, -O2, -O3) and does not appear with optimization disabled (-O0) This works for me on a x86_64 target. (In reply to comment #2) > This works for me on a x86_64 target. > For me it works on i686-pc-linux (with cross-compiler, configured with the same method as above - crosstool-0.43 + glibc-2.3.2), works on i386-mingw32 (with cross-compiler linux->mingw32), but does not work on powerpc. Still works for me on x86_64/i686. Any ppc guys around to confirm this? This works for me using latest mainline, but using a compiler built with revision 131553, it fails. I'll try and see if we're just getting lucky now or whether it has been fixed since then. Janis, in the meantime, can you run a reg hunt on the attached testcase starting at revision 131553? A regression hunt on powerpc-linux showed that the test starts passing with:
http://gcc.gnu.org/viewcvs?view=rev&rev=131823
r131823 | rguenth | 2008-01-25 12:06:31 +0000 (Fri, 25 Jan 2008)
That's a fix for 33887.
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test.cxx ------------------------------------------------------ #include <iostream> struct A { unsigned short x:14; unsigned short y:14; }; extern unsigned n; int main() { A a; a.x = n & 0x3FFF; a.y = (n>>14) & 0x3FFF; unsigned expected = n & 0x3FFF; if( a.x != expected ) { std::cout << "test failed: " << " (x=" << a.x << ") != " << expected << ", y=" << a.y << std::endl; return 1; } std::cout << "test succedeed" << std::endl; return 0; } unsigned n = 0xFE7B4873U; ------------------------------------------------------ output: test failed: (x=18547) != 2163, y=14829 14-bit unsigned field expands with non-zero padding bits appears with gcc-4.2.1, gcc-4.1.2, gcc-4.2-20070822 does not appear with gcc-3.4.6 gcc was configured and built with crosstool-0.43 (with glibc-2.3.2) powerpc-603-linux-gnu-g++ -v Using built-in specs. Target: powerpc-603-linux-gnu Configured with: /home/corpse/tmp/interlink/crosstool-0.43/build/powerpc-603-linux-gnu/gcc-4.2.1-glibc-2.3.2/gcc-4.2.1/configure --target=powerpc-603-linux-gnu --host=i686-host_pc-linux-gnu --prefix=/opt/compilers/gcc-4.2.1-glibc-2.3.2/powerpc-603-linux-gnu --with-cpu=603 --enable-cxx-flags=-mcpu=603 --with-headers=/opt/compilers/gcc-4.2.1-glibc-2.3.2/powerpc-603-linux-gnu/powerpc-603-linux-gnu/include --with-local-prefix=/opt/compilers/gcc-4.2.1-glibc-2.3.2/powerpc-603-linux-gnu/powerpc-603-linux-gnu --disable-nls --enable-threads=posix --enable-symvers=gnu --enable-__cxa_atexit --enable-languages=c,c++ --enable-shared --enable-c99 --enable-long-long Thread model: posix gcc version 4.2.1