[Bug tree-optimization/32544] gcc 4.2.1 miscompiles Mesa's r300 DRI driver with -ftree-vrp

[pixel at mandriva dot com]

------- Comment #6 from pixel at mandriva dot com  2007-08-07 22:41 -------
more info: the tree-vrp issue is raised by ivopts pass:

without ivopts:

  D.1541_13 = 3 - i_31;
  D.1542_14 = (unsigned int) D.1541_13;
  D.1543_15 = D.1542_14 * 4;
  D.1544_16 = (int *) D.1543_15;

with ivopts:

  D.1607_62 = (int *) i_31;
  D.1608_63 = D.1607_62 * -4B;
  D.1544_64 = D.1608_63 + 12B;
  D.1544_16 = D.1544_64;

  vrp finds that D.1608_63 is 0, and so replaces D.1544_64 with 12

  D.1607_62 = (int *) i_31;
  D.1608_63 = D.1607_62 * -4B;
  D.1544_64 = D.1608_63 + 12B;
  D.1544_16 = D.1544_64;


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32544