gcc/ChangeLog:
PR tree-optimization/20640
* tree-ssa-dce.c (remove_dead_stmt): Don't redirect edge to
post-dominator if it has phi nodes.
(eliminate_unnecessary_stmts): Remove dead phis in all blocks
before dead statements.
gcc/testsuite/ChangeLog:
PR tree-optimization/20640
* gcc.dg/torture/tree-loop-1.c: New.

From-SVN: r97446