Hi. There is a bug in AS, where AS translates fdivp and fsubp incorrectly, by translating fdivp (DE F9) to fdivrp (DE F1), and fsubp (DE E9) to fsubrp (DE E1).
Correct translation is found at http://download.intel.com/design/processor/manuals/253666.pdf <https://docs.google.com/viewer?url=http%3A%2F%2Fdownload.intel.com%2Fdesign%2Fprocessor%2Fmanuals%2F253666.pdf> Pages: fdivp: 3-373 fdivrp: 3-377 fsubp: 3-455 fsubrp: 3-459 System and AS-information: $ uname -a Linux Onyx 2.6.32-22-generic #36-Ubuntu SMP Thu Jun 3 22:02:19 UTC 2010 i686 GNU/Linux $ as -v GNU assembler version 2.20.1 (i486-linux-gnu) using BFD version (GNU Binutils for Ubuntu) 2.20.1-system.20100303 An assembly program that demonstrates the bug is the following: .globl fdiv fdiv: flds 4(%esp) flds 8(%esp) fdivp ret .globl fsub fsub: flds 4(%esp) flds 8(%esp) fsubp ret The generated code is: $ as -a --32 prog.s GAS LISTING prog.s page 1 1 .globl fdiv 2 fdiv: 3 0000 D9442404 flds 4(%esp) 4 0004 D9442408 flds 8(%esp) 5 0008 DEF1 fdivp 6 000a C3 ret 7 8 .globl fsub 9 fsub: 10 000b D9442404 flds 4(%esp) 11 000f D9442408 flds 8(%esp) 12 0013 DEE1 fsubp 13 0015 C3 ret 14 15 GAS LISTING prog.s page 2 DEFINED SYMBOLS prog.s:2 .text:0000000000000000 fdiv prog.s:9 .text:000000000000000b fsub NO UNDEFINED SYMBOLS Cheers, Marius Tennøe
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