+++ This bug was initially created as a clone of Bug #36133 +++ Hello,
The ASM code created by GCC 4.2.1 for 68k/Coldfire platform is not optimal. Comparing ASM output created by GCC 2.9 with GCC 4.2, the generated code got partially much worse with GCC 4. One problem that was visible a lot was that GCC uses suboptimal addressing modes. Please see the below example for details. In line 14 to line 2E this code was created: 14: 2290 movel %a0@,%a1@ 16: 2368 0004 0004 movel %a0@(4),%a1@(4) 1c: 2368 0008 0008 movel %a0@(8),%a1@(8) 22: 2368 000c 000c movel %a0@(12),%a1@(12) 28: d3fc 0000 0010 addal #16,%a1 2e: d1fc 0000 0010 addal #16,%a0 Much shorter and more efficient would have been this: 14: 20d9 movel [EMAIL PROTECTED],[EMAIL PROTECTED] 16: 20d9 movel [EMAIL PROTECTED],[EMAIL PROTECTED] 18: 20d9 movel [EMAIL PROTECTED],[EMAIL PROTECTED] 1a: 20d9 movel [EMAIL PROTECTED],[EMAIL PROTECTED] Example: C-source Code: void * copy_32x4a(void *destparam, const void *srcparam, size_t size) { int *dest = destparam; const int *src = srcparam; int size32; size32 = size / 16; for (; size32; size32--) { *dest++ = *src++; *dest++ = *src++; *dest++ = *src++; *dest++ = *src++; } } Compile option: m68k-linux-gnu-gcc -mcpu=54455 -msoft-float -o example -Os -fomit-frame-pointer example.c Code generated by GCC 4.2: 04: 202f 000c movel %sp@(12),%d0 08: 226f 0004 moveal %sp@(4),%a1 0c: 206f 0008 moveal %sp@(8),%a0 10: e888 lsrl #4,%d0 12: 6022 bras 36 14: 2290 movel %a0@,%a1@ 16: 2368 0004 0004 movel %a0@(4),%a1@(4) 1c: 2368 0008 0008 movel %a0@(8),%a1@(8) 22: 2368 000c 000c movel %a0@(12),%a1@(12) 28: d3fc 0000 0010 addal #16,%a1 2e: d1fc 0000 0010 addal #16,%a0 34: 5380 subql #1,%d0 36: 4a80 tstl %d0 38: 66da bnes 14 3a: 4e75 rts For comparison here is code that you would expect: 04: 202f 000c movel %sp@(12),%d0 08: 226f 0004 moveal %sp@(4),%a1 0c: 206f 0008 moveal %sp@(8),%a0 10: e888 lsrl #4,%d0 12: 6022 beq 20 14: 20d9 movel [EMAIL PROTECTED],[EMAIL PROTECTED] 16: 20d9 movel [EMAIL PROTECTED],[EMAIL PROTECTED] 18: 20d9 movel [EMAIL PROTECTED],[EMAIL PROTECTED] 1a: 20d9 movel [EMAIL PROTECTED],[EMAIL PROTECTED] 1c: 5380 subql #1,%d0 1e: 66da bnes 14 20: 4e75 rts Compiler used: m68k-linux-gnu-gcc -v Using built-in specs. Target: m68k-linux-gnu Configured with: /scratch/shinwell/cf-fall-linux-lite/src/gcc-4.2/configure --build=i686-pc-linux-gnu --host=i686-pc-linux-gnu --target=m68k-linux-gnu --enable-threads --disable-libmudflap --disable-libssp --disable-libgomp --disable-libstdcxx-pch --with-arch=cf --with-gnu-as --with-gnu-ld --enable-languages=c,c++ --enable-shared --enable-symvers=gnu --enable-__cxa_atexit --with-pkgversion=Sourcery G++ Lite 4.2-47 --with-bugurl=https://support.codesourcery.com/GNUToolchain/ --disable-nls --prefix=/opt/freescale/usr/local/gcc-4.2.47-eglibc-2.5.47/m68k-linux --with-sysroot=/opt/freescale/usr/local/gcc-4.2.47-eglibc-2.5.47/m68k-linux/m68k-linux-gnu/libc --with-build-sysroot=/scratch/shinwell/cf-fall-linux-lite/install/m68k-linux-gnu/libc --enable-poison-system-directories --with-build-time-tools=/scratch/shinwell/cf-fall-linux-lite/install/m68k-linux-gnu/bin --with-build-time-tools=/scratch/shinwell/cf-fall-linux-lite/install/m68k-linux-gnu/bin Thread model: posix gcc version 4.2.1 (Sourcery G++ Lite 4.2-47) I hope that this report help you to improve the quality of GCC. Kind regards Gunnar von Boehn -- P.S. I put the noticed issues in individual tickets for easier tracking. I hope that this is helpful to you. -- Summary: GCC creates suboptimal ASM : suboptimal Adressing-Modes used Product: gcc Version: 4.2.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: gunnar at greyhound-data dot com GCC build triplet: i686-pc-linux-gnu GCC host triplet: i686-pc-linux-gnu GCC target triplet: m68k-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36135