From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-193565-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 3591 invoked by alias); 10 Aug 2006 18:15:32 -0000
Received: (qmail 3563 invoked by uid 48); 10 Aug 2006 18:15:25 -0000
Date: Thu, 10 Aug 2006 18:15:00 -0000
Subject: [Bug middle-end/28685]  New: Multiple comparisons are not simplified
X-Bugzilla-Reason: CC
Message-ID: <bug-28685-1649@http.gcc.gnu.org/bugzilla/>
Reply-To: gcc-bugzilla@gcc.gnu.org
To: gcc-bugs@gcc.gnu.org
From: "uros at kss-loka dot si" <gcc-bugzilla@gcc.gnu.org>
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
X-SW-Source: 2006-08/txt/msg00797.txt.bz2
List-Id: <gcc-bugs.sourceware.org>

These two testcases should produce equivalent code:

int test(int a, int b)
{
  int lt = a < b;
  int eq = a == b;

  return (lt || eq);
}

int test_(int a, int b)
{
  return (a < b || a == b);
}

However, the optimized tree code is:

;; Function test (test)

Analyzing Edge Insertions.
test (a, b)
{
<bb 2>:
  return (a == b | a < b) != 0;

}

;; Function test_ (test_)

Analyzing Edge Insertions.
test_ (a, b)
{
<bb 2>:
  return a <= b;

}

And the resultinh x86_64 asm is unoptimal for test() function:

test:
        cmpl    %esi, %edi
        sete    %dl
        cmpl    %esi, %edi
        setl    %al
        orl     %edx, %eax
        movzbl  %al, %eax
        ret

test_:
        xorl    %eax, %eax
        cmpl    %esi, %edi
        setle   %al
        ret


-- 
           Summary: Multiple comparisons are not simplified
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: uros at kss-loka dot si
 GCC build triplet: x86_64-pc-linux-gnu
  GCC host triplet: x86_64-pc-linux-gnu
GCC target triplet: x86_64-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28685