-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 03/17/11 12:25, David Daney wrote: > On 03/17/2011 11:20 AM, McCall, Ronald SIK wrote: >>> If you let us in on what exactly the secret differences were, it would >>> be easier to opine on this topic. >> >> Sure thing! Here is an instruction sequence from the original Solaris >> toolchain: >> > > Resending to gcc@. I didn't really want a private message about it. > >> fe000230: 54 6a 87 be rlwinm r10,r3,16,30,31 >> fe000234: 65 49 ff ff oris r9,r10,65535 >> fe000238: 61 28 ff fc ori r8,r9,65532 >> fe00023c: 6d 07 80 00 xoris r7,r8,32768 >> fe000240: 3c 00 43 30 lis r0,17200 >> fe000244: 90 e1 00 0c stw r7,12(r1) >> fe000248: 90 01 00 08 stw r0,8(r1) >> fe00024c: 3c 80 fe 14 lis r4,-492 >> fe000250: c8 01 00 08 lfd f0,8(r1) >> fe000254: 39 24 82 38 addi r9,r4,-32200<<< Instruction >> sequence #1 >> fe000258: c8 89 00 00 lfd f4,0(r9)<<< (continued) >> fe00025c: 74 60 00 08 andis. r0,r3,8 >> fe000260: 3c c0 00 01 lis r6,1 >> fe000264: fc 60 20 28 fsub f3,f0,f4<<< Instruction sequence #2 >> fe000268: fc 40 18 18 frsp f2,f3 >> fe00026c: fc 20 10 90 fmr f1,f2 >> fe000270: fc 00 08 1e fctiwz f0,f1 >> fe000274: d8 01 00 10 stfd f0,16(r1) >> fe000278: 80 81 00 14 lwz r4,20(r1) >> fe00027c: 98 86 8f 0d stb r4,-28915(r6) >> fe000280: 41 82 00 cc beq- fe00034c >> >> Here is the same instruction sequence from the newly built Linux >> toolchain: >> >> fe000230: 54 6a 87 be rlwinm r10,r3,16,30,31 >> fe000234: 65 49 ff ff oris r9,r10,65535 >> fe000238: 61 28 ff fc ori r8,r9,65532 >> fe00023c: 6d 07 80 00 xoris r7,r8,32768 >> fe000240: 3c 00 43 30 lis r0,17200 >> fe000244: 90 e1 00 0c stw r7,12(r1) >> fe000248: 90 01 00 08 stw r0,8(r1) >> fe00024c: 3c 80 fe 14 lis r4,-492 >> fe000250: c8 01 00 08 lfd f0,8(r1) >> fe000254: c9 a4 87 b0 lfd f13,-30800(r4)<<< Instruction >> sequence #1 >> fe000258: fc 60 68 28 fsub f3,f0,f13<<< Instruction sequence #2 >> fe00025c: 74 60 00 08 andis. r0,r3,8 >> fe000260: 3c 80 00 01 lis r4,1 >> fe000264: fc 40 18 18 frsp f2,f3 >> fe000268: fc 20 10 90 fmr f1,f2 >> fe00026c: fc 00 08 1e fctiwz f0,f1 >> fe000270: d8 01 00 10 stfd f0,16(r1) >> fe000274: 80 e1 00 14 lwz r7,20(r1) >> fe000278: 98 e4 8f 0d stb r7,-28915(r4) >> fe00027c: 41 82 00 c8 beq- fe000344 >> >> Instruction sequence #1 has been combined into a single equivalent >> instruction. Instruction sequence #2 moved. Register usage is also >> different but equivalent. In my experience, there's all kinds of reasons why this can happen.
Use of floating point within the compiler (we generally avoid it), unstable qsort (again, we generally try to avoid it), hashing issues, particularly with pointers, etc etc. For those reasons and many more, we don't try to guarantee that a compiler running on different hosts will generate 100% identical target code. jeff -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJNglL7AAoJEBRtltQi2kC7kgsH/R1jVnxVlHimB09T56wJmU82 T3XtZRusl7j1vLNhzLDvxS+QpHz8bwL0mJFzDhJOtpPEm3gwTPQ9DSh32RGDbZ92 7ZgtsmHYTuSfZD2isUxLKBTi0PPs/Lv8bcmcwhhi11/QjppaLrQCycbzoALei4tF BB1feKLwoYQFWK6PuOcdB1TCJZd0frAjcu93qHDbq04CJj3/EGPqBzi/TcEkAL0S WQkWdmWtxKLtrT0dR+PiqO5PKdJ21Zl7qyIeOdFYepwYxQ7FjpAVMe1p4Wr7uc0J DVoApYBWmD+Nkv/pP4kDqKxWnp48Jtd95qKh9frgPpoaY+fCIKtSENFxKqTZt9c= =vHxO -----END PGP SIGNATURE-----
