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Date: Fri, 13 Aug 2004 16:42:00 -0000
From: "danfuzz at milk dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Message-ID: <20040813164249.17019.danfuzz@milk.com>
Reply-To: gcc-bugzilla@gcc.gnu.org
Subject: [Bug target/17019] New: THUMB -O1: bad code generated for simple for loop
X-Bugzilla-Reason: CC
X-SW-Source: 2004-08/txt/msg01290.txt.bz2
List-Id: <gcc-bugs.sourceware.org>

Compiling the following with -O1 for thumb results in bogus code being generated:

    void badness(int a)
    {
        void zorch(int b);
        int b;

        for (b = -1; b < a + 1; b++) {
            zorch(b);
        }
    }

In particular, it looks like the loop prologue code is screwed up and will cause the loop to always be 
skipped.

Here's how I configured and built the compiler:

$ tar -xjvf gcc-core-3.4.0.tar.bz2
$ cd gcc-3.4.0
$ ./configure --prefix=/usr/local/armdev --target=arm-elf --with-newlib --enable-languages=c

The following lines were uncommented in gcc/config/arm/t-arm-elf:

MULTILIB_OPTIONS    += mno-thumb-interwork/mthumb-interwork
MULTILIB_DIRNAMES   += normal interwork
MULTILIB_EXCEPTIONS += *mapcs-26/*mthumb-interwork*

$ make
$ sudo make install

In case it matters, I'm currently using binutils-2.15.

I will try this with 3.4.1 shortly.

-- 
           Summary: THUMB -O1: bad code generated for simple for loop
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: danfuzz at milk dot com
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: arm-unknown-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17019