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Date: Mon, 07 Jul 2003 22:34:00 -0000
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From: "pinskia at physics dot uc dot edu" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/11457] [3.3/3.4 Regression] redundant compare
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11457


pinskia at physics dot uc dot edu changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
          Component|optimization                |target
     Ever Confirmed|                            |1
           Keywords|                            |pessimizes-code
           Priority|P3                          |P2
   Last reconfirmed|0000-00-00 00:00:00         |2003-07-07 22:34:41
               date|                            |
            Summary|                            |[3.3/3.4 Regression]
                   |                            |redundant compare
   Target Milestone|---                         |3.4


------- Additional Comments From pinskia at physics dot uc dot edu  2003-07-07 22:34 -------
I can confirm this on 3.3.1 (20030616) and the mainline (20030707), 3.2.3, and 3.0.4 but 2.95.3 
did not produce the redundant compare so this is a regression.
On PPC, I do not get a redundant compare though:
_foo:
        cmpwi cr7,r3,0
        blt- cr7,L2
        bne- cr7,L3
        b L_zero$stub
L3:
        b L_non_negative$stub
L2:
        b L_negative$stub
Or on Vax:
foo:
        .word 0x0
        subl2 $4,%sp
        movl 4(%ap),%r0
        jlss .L2
        jneq .L3
        calls $0,zero
        ret
.L3:
        calls $0,non_negative
        ret
.L2:
        calls $0,negative
        ret
Or arm:
foo:
        @ args = 0, pretend = 0, frame = 0
        @ frame_needed = 0, uses_anonymous_args = 0
        @ link register save eliminated.
        cmp     r0, #0
        @ lr needed for prologue
        blt     .L2
        bne     .L3
        b       zero
.L3:
        b       non_negative
.L2:
        b       negative
So it looks very ia32 specific.