[Issue 9722] New: optimizer kills GOT to EBX load

Mar 14, 2013

Martin Nowak

Mar 14, 2013

Walter Bright

Mar 15, 2013

Mar 15, 2013

Mar 15, 2013

Mar 15, 2013

Mar 15, 2013

Mar 15, 2013

Mar 15, 2013

github-bugzilla@puremagic.com

Mar 19, 2013

Martin Nowak

March 14, 2013

[Issue 9722] New: optimizer kills GOT to EBX load

Posted by Martin Nowak

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Martin Nowak

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http://d.puremagic.com/issues/show_bug.cgi?id=9722

           Summary: optimizer kills GOT to EBX load
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Linux
            Status: NEW
          Severity: critical
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: code@dawg.eu


--- Comment #0 from Martin Nowak <code@dawg.eu> 2013-03-14 13:50:09 PDT ---
cat > bug.d << CODE
void foo()
{
    bar();
}

void bar()
{
}
CODE

--------------------
dmd -c -fPIC -m32 bug
--------------------
_D3bug3fooFZv PROC NEAR
        push    ebp                                     ; 0000 _ 55
        mov     ebp, esp                                ; 0001 _ 8B. EC
        sub     esp, 4                                  ; 0003 _ 83. EC, 04
        push    ebx                                     ; 0006 _ 53
        call    ?_003                                   ; 0007 _ E8, 00000000

?_003   LABEL NEAR
        pop     eax                                     ; 000C _ 58
        add     eax, offset _GLOBAL_OFFSET_TABLE_-$+1H  ; 000D _ 05,
00000002(GOT r)
        mov     dword ptr [ebp-4H], eax                 ; 0012 _ 89. 45, FC
        mov     ebx, dword ptr [ebp-4H]                 ; 0015 _ 8B. 5D, FC
        call    _D3bug3barFZv                           ; 0018 _ E8,
FFFFFFFC(PLT r)
        pop     ebx                                     ; 001D _ 5B
        leave                                           ; 001E _ C9
        ret                                             ; 001F _ C3
_D3bug3fooFZv ENDP
--------------------
dmd -c -fPIC -m32 -O bug
--------------------
_D3bug3fooFZv PROC NEAR
        push    ebp                                     ; 0000 _ 55
        mov     ebp, esp                                ; 0001 _ 8B. EC
        push    eax                                     ; 0003 _ 50
        push    ebx                                     ; 0004 _ 53
        call    _D3bug3barFZv                           ; 0005 _ E8,
FFFFFFFC(PLT r)
        pop     ebx                                     ; 000A _ 5B
        mov     esp, ebp                                ; 000B _ 8B. E5
        pop     ebp                                     ; 000D _ 5D
        ret                                             ; 000E _ C3
_D3bug3fooFZv ENDP

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http://d.puremagic.com/issues/show_bug.cgi?id=9722 Walter Bright <bugzilla@digitalmars.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |bugzilla@digitalmars.com --- Comment #1 from Walter Bright <bugzilla@digitalmars.com> 2013-03-14 16:12:56 PDT --- https://github.com/D-Programming-Language/dmd/pull/1748 -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=9722 --- Comment #2 from Martin Nowak <code@dawg.eu> 2013-03-14 20:15:11 PDT --- -------------------- dmd -c -fPIC -m32 -O bug -------------------- _D3bug3fooFZv PROC NEAR push ebp ; 0000 _ 55 mov ebp, esp ; 0001 _ 8B. EC push eax ; 0003 _ 50 push ebx ; 0004 _ 53 call ?_003 ; 0005 _ E8, 00000000 ?_003 LABEL NEAR pop ebx ; 000A _ 5B add ebx, offset _GLOBAL_OFFSET_TABLE_-$+1H ; 000B _ 81. C3, 00000003(GOT r) call _D3bug3barFZv ; 0011 _ E8, FFFFFFFC(PLT r) pop ebx ; 0016 _ 5B mov esp, ebp ; 0017 _ 8B. E5 pop ebp ; 0019 _ 5D ret ; 001A _ C3 _D3bug3fooFZv ENDP --- Comment #3 from github-bugzilla@puremagic.com 2013-03-14 20:15:12 PDT --- Commits pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/c3fa2edf6a1881f59afdcf101ba0f4a592f62c67 fix Issue 9722 - optimizer kills GOT to EBX load https://github.com/D-Programming-Language/dmd/commit/28b16887c2007838e7bae7aff6e26aec5466398b Merge pull request #1748 from WalterBright/fix9722 fix Issue 9722 - optimizer kills GOT to EBX load -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=9722 Martin Nowak <code@dawg.eu> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution| |FIXED -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=9722 --- Comment #4 from Walter Bright <bugzilla@digitalmars.com> 2013-03-15 11:01:20 PDT --- Martin, are you saying this bug should still be open? -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=9722 --- Comment #5 from Martin Nowak <code@dawg.eu> 2013-03-15 13:48:10 PDT --- (In reply to comment #4) > Martin, are you saying this bug should still be open? No, the bug is fixed but it's terribly inefficient when the GOT isn't cached. What happens now is that the optimizer kills the unreferenced localgot variable and instead the GOT address is loaded anew for every access. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=9722 Martin Nowak <code@dawg.eu> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |REOPENED Resolution|FIXED | --- Comment #6 from Martin Nowak <code@dawg.eu> 2013-03-15 14:25:05 PDT --- A slightly different case of the bug that still happens. I haven't had time to reduce it yet though. -------------------- dmd -c -m32 -fPIC -O druntime/src/core/runtime.d -------------------- runModuleUnitTests PROC NEAR push ebp ; 0000 _ 55 mov ebp, esp ; 0001 _ 8B. EC sub esp, 436 ; 0003 _ 81. EC, 000001B4 push ebx ; 0009 _ 53 mov ecx, 35 ; 000A _ B9, 00000023 xor eax, eax ; 000F _ 31. C0 push esi ; 0011 _ 56 push edi ; 0012 _ 57 lea edi, [ebp-1B4H] ; 0013 _ 8D. BD, FFFFFE4C rep stosd ; 0019 _ F3: AB lea ecx, [ebp-1B0H] ; 001B _ 8D. 8D, FFFFFE50 push ecx ; 0021 _ 51 mov ebx, dword ptr [ebp-4H] ; 0022 _ 8B. 5D, FC call sigfillset ; 0025 _ E8, FFFFFFFC(PLT r) ... The instruction that loads the GOT address from the stack is there but the part that stores it on the stack has been optimized away. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=9722 --- Comment #7 from github-bugzilla@puremagic.com 2013-03-15 14:40:24 PDT --- Commit pushed to dmd-1.x at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/1ab4ee51bcb6821c368c58fc9ac9672f69b12340 Merge pull request #1748 from WalterBright/fix9722 fix Issue 9722 - optimizer kills GOT to EBX load -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

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