[Bug tree-optimization/51136] [4.7 Regression] ICE: SIGSEGV in unlink_virtual_phi (tree-flow-inline.h:427) with -O2 -fno-tree-dominator-opts (-ftree-tail-merge)

[vries at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51136

--- Comment #1 from vries at gcc dot gnu.org 2011-11-15 14:00:44 UTC ---
Created attachment 25827
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=25827
tentative patch

The problem is that in update_vuses, we're removing the def of the
def-use-chain we're walking with
FOR_EACH_IMM_USE_STMT/FOR_EACH_IMM_USE_ON_STMT.

Postponing the removal till after we've walked all the uses fixes the problem.