[LLVMbugs] [Bug 3560] New: fpmath code generation performance issue

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=3560

           Summary: fpmath code generation performance issue
           Product: tools
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: llvm-gcc
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: j at jawed.name
                CC: llvmbugs at cs.uiuc.edu


Experiencing a 2x slowdown with nested loops in PHP source.

1) grab the php source (http://snaps.php.net)
2) tar xjvf php5.3[...].tar.bz2
3) cd php5.3[...]
4) ./configure --enable-debug --enable-cli --disable-all --without-sqlite3
5) make && make install && make test

ZEND_POST_INC_SPEC_CV_HANDLER is poorly generated, llvm-gcc generates x86 asm
which uses fldl/fstpl vs gcc which does not (and consequently does not
experience the slowdown).

The test in question is nestedloop(12), performs better/on par with gcc with
>=msse2.


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