Date: Fri, 28 May 1999 01:17:31 +0200
From: Ronald de Man <deman AT win DOT tue DOT nl>
To: pgcc AT delorie DOT com
Subject: -fcompare-elim
Message-ID: <19990528011731.A22985@win.tue.nl>
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The following little program triggers a bug in pgcc-1.1.3 when
compiled with -O2 -fcompare-elim:

-----

#define bit(x) bitjes[x];

long long bitjes[64];
long long mvs[64][8];

void SetUp()
{
  int b,x,y,z,b2;
  long long board;

  for (b = 0; b < 64; b++) {
    b2 = b << 1;
    for ( y = 0; y < 64; y += 8) {
      board = 0;
      x = y + 8;
      z = (y>>3) + 1;
      while (x < 64) {
        board |= bit(x);
        if (b2 & (1<<z)) break;
        x += 8;
        z++;
      }
      x = y-8;
      z = (y>>3)-1;
      while (x >= 0) {
        board |= bit(x);
        if (b2 & (1<<z)) break;
        x -= 8;
        z--;
      }
      mvs[b][y>>3] = board;
    }
  }
}

main()
{
  int i, j;

  for (i = 0; i < 64; i++)
    bitjes[i] = 1ULL << i;

  SetUp();

  for (i = 0; i < 64; i++)
    for (j = 0; j < 8; j++)
      printf("%2d  %d  %lld\n", i, j, mvs[i][j]);
}

-----

Running the program should give some output, but when compiled
with -O2 -fcompare-elim it crashes at the line

	mvs[b][y>>3] = board;

with for b a value of -64. Indeed, looking at the assembly output,
it seems pgcc lets b run from -64 to 63.

I do not know if this also happens with egcs-1.1.2. Version 1.1.1
of pgcc does not have problems here.

Ronald