[Bug rtl-optimization/23102] New: extra XORs generated on i686

[dann at godzilla dot ics dot uci dot edu]

Compiling the code below (extracted from xterm-202) with
 -fno-inline -O2 -march=i686

typedef unsigned int Cardinal;
typedef unsigned long Pixel;
typedef char *String;

typedef struct {
 String resource;
 Pixel value;
 int mode;
} ColorRes;

typedef struct {
 ColorRes Acolors[(256 +4)];
 int startHRow, startHCol,
   endHRow, endHCol,
   startHCoord, endHCoord;
 Cardinal selection_count;
} TScreen;

static void
ResetSelectionState(TScreen * screen)
{
    screen->selection_count = 0;
    screen->startHRow = screen->startHCol = 0;
    screen->endHRow = screen->endHCol = 0;
}

void foo (TScreen *scr)
{
  ResetSelectionState (scr);
}

generates: 
ResetSelectionState:
        pushl   %ebp
        xorl    %edx, %edx
        movl    %esp, %ebp
        xorl    %ecx, %ecx
        popl    %ebp
        movl    %edx, 3144(%eax)
        xorl    %edx, %edx
        movl    %ecx, 3124(%eax)
        xorl    %ecx, %ecx   ;; this is not needed, ecx is already 0 
        movl    %edx, 3120(%eax)
        xorl    %edx, %edx    ;; so is edx
        movl    %ecx, 3132(%eax)  
        movl    %edx, 3128(%eax)
        ret

when using -march=i386 the code looks better:

ResetSelectionState:
        pushl   %ebp
        movl    %esp, %ebp
        movl    $0, 3144(%eax)
        movl    $0, 3124(%eax)
        movl    $0, 3120(%eax)
        movl    $0, 3132(%eax)
        movl    $0, 3128(%eax)
        leave
        ret

-- 
           Summary: extra XORs  generated on i686
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dann at godzilla dot ics dot uci dot edu
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23102