Fix PR tree-optimization/63184: add simplification of (& + A) != (& + B)

These two testcases have been failing since GCC 5 but things
have improved such that adding a simplification to match.pd
for this case is easier than before.
In the end we have the following IR:
....
  _5 = &a[1] + _4;
  _7 = &a + _13;
  if (_5 != _7)

So we can fold the _5 != _7 into:
(&a[1] - &a) + _4 != _13

The subtraction is folded into constant by ptr_difference_const.
In this case, the full expression gets folded into a constant
and we are able to remove the if statement.

OK? Bootstrapped and tested on aarch64-linux-gnu with no regressions.

gcc/ChangeLog:

	PR tree-optimization/63184
	* match.pd: Add simplification of pointer_diff of two pointer_plus
	with addr_expr in the first operand of each pointer_plus.
	Add simplificatoin of ne/eq of two pointer_plus with addr_expr
	in the first operand of each pointer_plus.

gcc/testsuite/ChangeLog:

	PR tree-optimization/63184
	* c-c++-common/pr19807-2.c: Enable for all targets and remove the xfail.
	* c-c++-common/pr19807-3.c: Likewise.

1 files changed, 15 insertions, 0 deletions

diff --git a/gcc/match.pd b/gcc/match.pd
index f920bc4..cc7809d 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -2063,6 +2063,21 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
    (if (ptr_difference_const (@0, @1, &diff))
     { build_int_cst_type (type, diff); }))))
 
+/* (&a+b) - (&a[1] + c) -> sizeof(a[0]) + (b - c) */
+(simplify
+ (pointer_diff (pointer_plus ADDR_EXPR@0 @1) (pointer_plus ADDR_EXPR@2 @3))
+ (with { poly_int64 diff; }
+   (if (ptr_difference_const (@0, @2, &diff))
+    (plus { build_int_cst_type (type, diff); } (convert (minus @1 @3))))))
+
+/* (&a+b) !=/== (&a[1] + c) ->  sizeof(a[0]) + b !=/== c */
+(for neeq (ne eq)
+ (simplify
+  (neeq (pointer_plus ADDR_EXPR@0 @1) (pointer_plus ADDR_EXPR@2 @3))
+   (with { poly_int64 diff; tree inner_type = TREE_TYPE (@1);}
+    (if (ptr_difference_const (@0, @2, &diff))
+     (neeq (plus { build_int_cst_type (inner_type, diff); } @1) @3)))))
+
 /* Canonicalize (T *)(ptr - ptr-cst) to &MEM[ptr + -ptr-cst].  */
 (simplify
  (convert (pointer_diff @0 INTEGER_CST@1))