Hi,



This patch adds a very simple early vrp implementation. This visits the 
basic blocks in the dominance order and set the Value Ranges (VR) for

SSA_NAMEs in the scope. Use this VR to discover more VRs. Restore the 
old VR once the scope is exit.



Thanks,

Kugan





gcc/ChangeLog:



2016-07-14  Kugan Vivekanandarajah  <kuganv@linaro.org>



         * Makefile.in: Add tree-early-vrp.o.

         * common.opt: New option -ftree-evrp.

         * doc/invoke.texi: Document -ftree-evrp.

         * passes.def: Define new pass_early_vrp.

         * timevar.def: Define new TV_TREE_EARLY_VRP.

         * tree-early-vrp.c: New file.

         * tree-pass.h (make_pass_early_vrp): New.



gcc/testsuite/ChangeLog:



2016-07-14  Kugan Vivekanandarajah  <kuganv@linaro.org>



         * gcc.dg/tree-ssa/evrp1.c: New test.

         * gcc.dg/tree-ssa/evrp2.c: New test.

         * gcc.dg/tree-ssa/evrp3.c: New test.

         * g++.dg/tree-ssa/pr31146-2.C: Run with -fno-tree-evrp as evrp also

         does the same transformation.

         * gcc.dg/tree-ssa/pr20318.c: Check for the pattern in evrp dump.

         * gcc.dg/tree-ssa/pr22117.c: Likewise.

         * gcc.dg/tree-ssa/pr25382.c: Likewise.

         * gcc.dg/tree-ssa/pr68431.c: LIkewise.

         * gcc.dg/tree-ssa/vrp19.c: Likewise.

         * gcc.dg/tree-ssa/vrp23.c: Likewise.

         * gcc.dg/tree-ssa/vrp24.c: Likewise.

         * gcc.dg/tree-ssa/vrp58.c: Likewise.

         * gcc.dg/tree-ssa/vrp67.c: Likewise.

         * gcc.dg/tree-ssa/vrp98.c: Likewise.