[GSoC][match-and-simplify] add few constant-folding tests

[Prathamesh Kulkarni <bilbotheelffriend at gmail dot com>]

[gcc/testsuite/gcc.dg/tree-ssa]
  * match-constant-folding.c: New test-case.

Thanks,
Prathamesh

Index: gcc/testsuite/gcc.dg/tree-ssa/match-constant-folding.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/match-constant-folding.c	(revision 0)
+++ gcc/testsuite/gcc.dg/tree-ssa/match-constant-folding.c	(working copy)
@@ -0,0 +1,58 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-ccp-details -fdump-tree-forwprop-details" }  */
+
+/* x + 0 -> x */
+int c1(int x)
+{
+  int t1 = 0;
+  int c1_val = x + t1;
+  return c1_val;
+}
+/* { dg-final { scan-tree-dump "Match-and-simplified x_\\d\+\\(D\\) \\+ t1_\\d\+ to x_\\d\+\\(D\\)" "ccp1" } } */ 
+
+/* x ptrplus 0 -> x */
+char *c2(char *p)
+{
+  int t1 = 0;
+  char *c2_val = p + t1;
+  return c2_val;
+}
+/* { dg-final { scan-tree-dump "Match-and-simplified p_\\d\+\\(D\\) \\+ _\\d\+ to p_\\d\+\\(D\\)" "ccp1" } } */
+
+/* x - 0 -> x */ 
+int c3(int x)
+{
+  int t1 = 0;
+  int c3_val = x - t1;  
+  return c3_val;
+}
+/* { dg-final { scan-tree-dump "Match-and-simplified x_\\d\+\\(D\\) - t1_\\d\+ to x_\\d\+\\(D\\)" "ccp1" } } */
+
+/* x - x -> 0 */
+int c4(int x)
+{
+  int t1 = x;
+  int c4_val = x - t1;
+  return c4_val;
+}
+/* { dg-final { scan-tree-dump "gimple_simplified to c4_val_\\d\+ = 0" "forwprop1" } } */
+
+/* x * 0 -> 0 */
+int c5(int x)
+{
+  int t1 = 0;
+  int c5_val = x * t1;
+  return c5_val;
+}
+/* { dg-final { scan-tree-dump "Match-and-simplified x_\\d\+\\(D\\) \\* t1_\\d\+ to 0" "ccp1" } } */
+
+/* x * 1 -> x */
+int c6(int x)
+{
+  int t1 = 1;
+  int c6_val = x * t1;
+  return c6_val;
+}
+/* { dg-final { scan-tree-dump "Match-and-simplified x_\\d\+\\(D\\) \\* t1_\\d\+ to x_\\d\+\\(D\\)" "ccp1" } } */
+
+/* { dg-final { cleanup-tree-dump "forwprop2" } } */