Check to see if null pointer is dereferenceable [PR102630].

Resolves:
PR middle-end/102630 - Spurious -Warray-bounds with named address space

gcc/ChangeLog:

	PR middle-end/102630
	* pointer-query.cc (compute_objsize_r): Handle named address spaces.

gcc/testsuite/ChangeLog:

	PR middle-end/102630
	* gcc.dg/Warray-bounds-90.c: New test.

diff --git a/gcc/pointer-query.cc b/gcc/pointer-query.cc
index 83b1f0fc866..910f452868e 100644
--- a/gcc/pointer-query.cc
+++ b/gcc/pointer-query.cc
@@ -41,6 +41,7 @@
 #include "pointer-query.h"
 #include "tree-pretty-print.h"
 #include "tree-ssanames.h"
+#include "target.h"
 
 static bool compute_objsize_r (tree, int, access_ref *, ssa_name_limit_t &,
 			       pointer_query *);
@@ -1869,13 +1870,24 @@ compute_objsize_r (tree ptr, int ostype, access_ref *pref,
   if (code == INTEGER_CST)
     {
       /* Pointer constants other than null are most likely the result
-	 of erroneous null pointer addition/subtraction.  Set size to
-	 zero.  For null pointers, set size to the maximum for now
-	 since those may be the result of jump threading.  */
+	 of erroneous null pointer addition/subtraction.  Unless zero
+	 is a valid address set size to zero.  For null pointers, set
+	 size to the maximum for now since those may be the result of
+	 jump threading.  */
       if (integer_zerop (ptr))
 	pref->set_max_size_range ();
+      else if (POINTER_TYPE_P (TREE_TYPE (ptr)))
+	{
+	  tree deref_type = TREE_TYPE (TREE_TYPE (ptr));
+	  addr_space_t as = TYPE_ADDR_SPACE (deref_type);
+	  if (targetm.addr_space.zero_address_valid (as))
+	    pref->set_max_size_range ();
+	  else
+	    pref->sizrng[0] = pref->sizrng[1] = 0;
+	}
       else
 	pref->sizrng[0] = pref->sizrng[1] = 0;
+
       pref->ref = ptr;
 
       return true;
diff --git a/gcc/testsuite/gcc.dg/Warray-bounds-90.c b/gcc/testsuite/gcc.dg/Warray-bounds-90.c
new file mode 100644
index 00000000000..93461d4b238
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Warray-bounds-90.c
@@ -0,0 +1,31 @@
+/* PR middle-end/102630 - spurious -Warray-bounds with named address space
+   { dg-do compile }
+   { dg-options "-O2 -Wall" } */
+
+void sink (void*, ...);
+#define sink(...) sink (0, __VA_ARGS__)
+
+
+void test_generic_null (void)
+{
+  // We want some warning here but -Warray-bounds may not be it.
+  *(char*)0 = 0;              // { dg-warning "" "pr??????" { xfail *-*-* } }
+}
+
+void test_generic_cstaddr (void)
+{
+  /* We get -Warray-bounds (-Wstringop-overflow in GCC 11) but some
+     other warning might be preferable.  */
+  *(char*)1234 = 1;           // { dg-warning "" }
+}
+
+
+void test_named_address_space_null (void)
+{
+  *(char __seg_fs*)0 = 0;     // no warning (intentional)
+}
+
+void test_named_address_space_cstaddr (void)
+{
+  *(char __seg_fs*)1234 = 0;  // { dg-bogus "-Warray-bounds" }
+}