Hi... I'm using debian's unstable gcc 4.0: $ gcc -v Using built-in specs. Target: i486-linux-gnu Configured with: ../src/configure -v --enable-languages=c,c++,java,f95,objc,ada,treelang --prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib --enable-nls --without-included-gettext --enable-threads=posix --program-suffix=-4.0 --enable-__cxa_atexit --enable-libstdcxx-allocator=mt --enable-clocale=gnu --enable-libstdcxx-debug --enable-java-gc=boehm --enable-java-awt=gtk --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-4.0-1.4.2.0/jre --enable-mpfr --disable-werror --enable-checking=release i486-linux-gnu Thread model: posix gcc version 4.0.1 20050701 (prerelease) (Debian 4.0.0-12)
I'm trying to compile the following code (which is a reduced test case generated from mercury_deep_copy.c in the Mercury compiler version ROTD 20050707 from http://www.cs.mu.oz.au/mercury/): register unsigned int reg0 __asm__("esi"); register unsigned int reg1 __asm__("edi"); register unsigned int reg2 __asm__("ebx"); static unsigned int MR_deep_copy_typeclass_info(unsigned int *typeclass_info, void *lower_limit, void *upper_limit) { int i; for (i = 5; i > 0; i--) { typeclass_info[i] = (unsigned int) MR_deep_copy_typeclass_info( (unsigned int *)typeclass_info[i], lower_limit, lower_limit); } return 0; } unsigned int func(void) { return MR_deep_copy_typeclass_info(0, 0, 0); } using this command line: $ gcc -c test3.c -O -funit-at-a-time which produces this: test3.c: In function 'MR_deep_copy_typeclass_info': test3.c:17: error: unable to find a register to spill in class 'GENERAL_REGS' test3.c:17: error: this is the insn: (insn 27 26 28 1 (set (reg:SI 0 ax) (mem:SI (plus:SI (reg:SI 70) (const_int 4 [0x4])) [0 S4 A32])) 41 {*movsi_1} (insn_list:REG_DEP_TRUE 22 (nil)) (nil)) test3.c:17: confused by earlier errors, bailing out The same code compiles with -O1 and no -funit-at-a-time. It also compiles with gcc-3.4, so this is a gcc 4 regression. I suspect this means -funit-at-a-time behaves badly under high register pressure. =) Peter -- Summary: Register allocation problem in combination with -funit- at-a-time and global register variables Product: gcc Version: 4.0.0 Status: UNCONFIRMED Severity: normal Priority: P2 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: peter at hawkins dot emu dot id dot au CC: gcc-bugs at gcc dot gnu dot org GCC build triplet: i686-pc-linux-gnu GCC host triplet: i686-pc-linux-gnu GCC target triplet: i686-pc-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22362
