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Date: Tue, 14 Jul 2009 17:09:00 -0000
Subject: [Bug c/40748]  New: simple switch/case, if/else and arithmetics result in different code
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Tested r149624, 4.4.0 and 4.3.3

# ./gcc -v
Using built-in specs.
Target: x86_64-unknown-linux-gnu
Configured with: ../configure --enable-languages=c,c++
--prefix=/mnt/svn/gcc-trunk/build/
Thread model: posix
gcc version 4.5.0 20090714 (experimental) (GCC)

4.4.0 and 4.5 have better behaviour in the case of "switch"

The following code:
-------------------------------
unsigned f1(unsigned i)
{
        switch (i) {
                case 0: return 0;
                case 1: return 1;
                case 2: return 2;
                case 3: return 3;
                default: return 4;
        }
}

unsigned f2(unsigned i)
{
        if (i == 0) return 0;
        if (i == 1) return 1;
        if (i == 2) return 2;
        if (i == 3) return 3;
        return 4;
}

unsigned f3(unsigned i)
{
        return i < 4 ? i : 4;
}
-------------------------------

f1(), f2() and f3() do the same, but the resulting code differs a lot.


-- 
           Summary: simple switch/case, if/else and arithmetics result in
                    different code
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: zsojka at seznam dot cz
  GCC host triplet: x86_64-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40748