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Re: Softfloat miscompiled by gcc 4.5.x

(2012/10/01 17:08), Martin Husemann wrote:
On Mon, Oct 01, 2012 at 07:45:01AM +0100, David Laight wrote:
I don't call that a fix.

Neither do I.

There is either a bug in gcc (which will affect other code), or bugs
in the softfloat code itself - which will appear again later.

Yes - my bet is on the former for now.

 I debugged this.

        The problem occurs with -O1 -ftree-vrp.

        The problem doesn't occur with -O2 -fno-tree-vrp.

        The problem doesn't occur when SOFTFLOAT_BITS=64
        (Note that only arm and emips set it with 64)

 How about COPTS.softfloat.c+=-fno-tree-vrp?

The ATF test result in /usr/tests/lib/libm was as follows (netbsd-6):

Summary for 20 test programs:
    311 passed test cases.
    0 failed test cases.      <======== Changed from 16 to 0
    4 expected failed test cases.
    5 skipped test cases.

Shouldn't be too hard to isolate 1 buggy file and work out exactly
where it goes wrong.
I'd guess a 'strict aliasing' issue....

For someone with enough arm asm fu - probably. The differences in the
generated asm are "not small" though, and unfortunately I don't have time
to look at details right now. Volunteers welcome...


                SAITOH Masanobu (msaitoh%execsw.org@localhost

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