[LLVMbugs] [Bug 9658] New: Probably inefficient code generation

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Fri Apr 8 06:14:16 PDT 2011


           Summary: Probably inefficient code generation
           Product: new-bugs
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: eugeny.grishul at gmail.com
                CC: llvmbugs at cs.uiuc.edu

Working on my compiler(http://code.google.com/p/bamelg/) I found that sometimes
LLVM generates TOO many movb's
    movb    $0, 209(%esp)
    movb    $0, 208(%esp)
    movb    $0, 207(%esp)
    movb    $0, 206(%esp)
    movb    $0, 205(%esp)
    movb    $0, 204(%esp)
    movb    $0, 203(%esp)

following each other. ( total of ~500Kb of compiled movbs! )

Tested with rev 129071.
1. `llc -O=3 -march=x86 test.bc -O=3 -o test.s`
2. see test.s line 287-4403 ( also 47497-84488 )

PS. Code from real app and I have no idea how to reduce bytecode file to repro

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