[Bug tree-optimization/49419] [4.6/4.7 regression] gcc -O2 miscompiles gp2c

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49419

--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-06-16 18:18:55 UTC ---
Created attachment 24548
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24548
gcc47-vrp.patch

So, I've tried this patch for extract_range_from_assert.
It bootstrapped/regtested on x86_64-linux and i686-linux, but regressed
FAIL: g++.dg/tree-ssa/pr18178.C scan-tree-dump-times vrp1 "if " 1
(just the vrp1 dump checking and code removal, the assembly is the same at the
end).
The VR is just different (- is vanilla, + is with the patch).
 Value ranges after VRP:

-i_1: [0, +INF(OVF)]
+i_1: [0, +INF]
 a_3(D): VARYING
 D.2084_4: VARYING
 D.2090_7: VARYING
@@ -681,10 +927,10 @@ D.2094_11: VARYING
 i_12: [1, +INF(OVF)]
 D.2077_13: VARYING
 .MEM_14: VARYING
-i_19: [-INF, D.2084_4 + -1]  EQUIVALENCES: { i_1 } (1 elements)
-i_20: [0, +INF]  EQUIVALENCES: { i_1 i_19 } (2 elements)
+i_19: [0, +INF]  EQUIVALENCES: { } (0 elements)
+i_20: [0, +INF]  EQUIVALENCES: { i_19 } (1 elements)
 a_21: ~[0B, 0B]  EQUIVALENCES: { a_3(D) } (1 elements)
-D.2084_22: [i_19 + 1, +INF]  EQUIVALENCES: { D.2084_4 } (1 elements)
+D.2084_22: [1, +INF]  EQUIVALENCES: { D.2084_4 } (1 elements)
 D.2077_23: ~[0B, 0B]  EQUIVALENCES: { D.2077_13 } (1 elements)

but resulted in:
 Folding statement: if (i_20 >= D.2084_22)
-Folding predicate i_20 >= D.2084_22 to 0
-Folded into: if (0 != 0)
-
+Not folded

So, not sure if I should push this anyway (with adjusting/removing the
testcase), or not.