llvm dev - May 2004 - [LLVMdev] Plea for help

OK, details:

I run RH8 (gcc 3.2.something), RH9 (gcc 3.2.2-5) and Fedora.
Problems are the same across all setups. Hardware is Athlon 1600+
and half a giga RAM. Runs fail with an assertion when the linear
scan allocator is enabled, but runs without problems otherwise.

On RH9 (the system I have access to while generating this email) I
have the following details:

 > 1) The LLVM assembly language (.ll file) that is failing.
 - Attached.

 > 2) The version of GCC that you are using (gcc -v)
----------------
[finna at coplin11 ~]$ gcc -v
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/3.2.2/specs
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man 
--infodir=/usr/share/info --enable-shared --enable-threads=posix 
--disable-checking --with-system-zlib --enable-__cxa_atexit 
--host=i386-redhat-linux
Thread model: posix
gcc version 3.2.2 20030222 (Red Hat Linux 3.2.2-5)

 > 3) A brief description of your hardware, especially if it is 
something uncommon. 
 > I'm assuming your running on x86.  Running on another processor (like 
Sparc
 > or even AMD's new 64 bit chips) might make a difference.
-------------
Its a plain athlon (actually there are two plain athlons, one running 
1.2GHz,
the other running 1.0GHz). Hardware has been used for more than a year
running heavyweight programs (chip design cad tools, for example).

 > 4) The exact command line that you use to configure LLVM, as well as the
 > name of the source and object directory names you use to store the 
source
 > and object files.
-------------
Under my home dir, /home/finna I have a 'llvm' dir containing
   * a 'build' dir, this is supposed to be the object dir in your 
description,
   * a 'cfrontend' dir, generated by extracting the 1.2 release of the 
cfrontend
   * a 'llvm' dir, generated by getting latest cvs checkout
Standing in 'build' (/home/finna/llvm/build) I run
[finna at coplin11 build]$ ../llvm/configure 
--with-llvmgccdir=/home/finna/llvm/cfrontend/x86/llvm-gcc/
(then gmake and gmake install).

Environment variables:
LLVM_LIB_SEARCH_PATH=/home/finna/llvm/cfrontend/x86/llvm-gcc/bytecode-libs

And aliases:
llvmg++ /home/finna/llvm/cfrontend/x86/llvm-gcc/bin/g++
llvmgcc /home/finna/llvm/cfrontend/x86/llvm-gcc/bin/gcc


 > 5) A copy of the Makefile.config file that is created in
 > the object root directory after running configure.
-------------
- attached.

Chris wrote in a followup:
> Can you send the output of 'llc -o - foo.bc -debug
-print-machineinstrs'?

Attached as "linscan". (But added the "-regalloc=linearscan"
to provoke
the error).

For completenes, I also attach the a.out.bc bytecode, although I expect 
it can be generated
from a.out.ll.

--------------

That's it. I want to thank you very much for offering
this kind of support. I hope it won't be too embarrasing
for me when you find the error.

Best regards
/Finn

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Dear Mr. Andersen:

Quick question:

Have you ever built the LLVM source code in /home/finna/llvm (i.e. the 
source directory)?  If so, did you clean it out (make distclean) before 
switching over to /home/finna/build as the object tree?

-- John T.

-- 
*********************************************************************
* John T. Criswell                         Email: criswell at uiuc.edu *
* Research Programmer                                               *
* University of Illinois at Urbana-Champaign                        *
*                                                                   *
* "It's today!" said Piglet. "My favorite day," said
Pooh.          *
*********************************************************************

On Tue, 4 May 2004, Finn S Andersen wrote:
> Chris wrote in a followup:
>
> > Can you send the output of 'llc -o - foo.bc -debug
-print-machineinstrs'?
>
>
> Attached as "linscan". (But added the
"-regalloc=linearscan" to provoke
> the error).
Yes, that's exactly what I meant... thanks for reading my mind!  :)

It looks like this is where things start to go downhill
(LiveIntervals.cpp:559):

LiveIntervals::Interval::Interval(unsigned r)
    : reg(r),
      weight((MRegisterInfo::isPhysicalRegister(r) ?
              std::numeric_limits<float>::infinity() : 0.0F))
{


For a physical register (EDX in this case) it appears that the interval is
being created, but gets a 0 weight instead of an infinity weight.  This
implies that the MRegisterInfo::isPhysicalRegister might have an issue, or
std::numeric_limits has an issue.

Could you try compiling and running this program:

---
#include <limits>
#include <iostream>
int main() {
  std::cerr << std::numeric_limits<float>::infinity() <<
"\n";
}
---

If that prints 'inf', then check include/llvm/Target/MRegisterInfo.h,
and
make sure you see something like this in it:

  /// isPhysicalRegister - Return true if the specified register number is in
  /// the physical register namespace.
  static bool isPhysicalRegister(unsigned Reg) {
    assert(Reg && "this is not a register!");
    return Reg < FirstVirtualRegister;
  }


If that looks fine, try changing LiveIntervals::Interval::Interval in
lib/CodeGen/LiveIntervals.cpp to this:

LiveIntervals::Interval::Interval(unsigned r)
    : reg(r),
      weight((MRegisterInfo::isPhysicalRegister(r) ?
              std::numeric_limits<float>::infinity() : 0.0F))
{
  std::cerr << "Created interval for reg " << reg <<
" weight = " << weight
            << "\n";
  assert(r < 1024 || weight > 1 && "physreg or weight
incorrectly computed!");
}


And send me the output of -debug -print-machineinstrs -regalloc-linearscan
again.  :)

Thanks, I hope we can get this resolved once and for all!

-Chris

-- 
http://llvm.cs.uiuc.edu/
http://www.nondot.org/~sabre/Projects/

On Tue, 4 May 2004, Chris Lattner wrote:
>   std::cerr << "Created interval for reg " << reg
<< " weight = " << weight
>             << "\n";
>   assert(r < 1024 || weight > 1 && "physreg or weight
incorrectly computed!");
Whoops, that should have parens:
  assert((r < 1024 || weight > 1) && "physreg or weight
incorrectly computed!");

Sorry about that.  :)

-Chris

-- 
http://llvm.cs.uiuc.edu/
http://www.nondot.org/~sabre/Projects/

Chris Lattner wrote:
>Could you try compiling and running this program:
>
>---
>#include <limits>
>#include <iostream>
>int main() {
>  std::cerr << std::numeric_limits<float>::infinity() <<
"\n";
>}
>---
>  
>
Sure thing. It prints "0". Calling that inifinity is somewhat
of a stretch, isn't it ?

What on earth is going on here?

Log:
----------

[finna at coplin11 debug]$ cat - > tst.cpp
#include <limits>
#include <iostream>
int main() {
  std::cerr << std::numeric_limits<float>::infinity() <<
"\n";
}
[finna at coplin11 debug]$ g++ tst.cpp
[finna at coplin11 debug]$ ./a.out
0

----------
Thanks a lot for your time and dedication on this subject.

Best regards
/Finn