Improve DSE which in turn eliminates the need for jump threading and block…

Improve DSE which in turn eliminates the need for jump threading and block duplication for the original testcase in pr89689 which in turn eliminates the false positive -Warray-bounds warning for the original testcase.

	PR tree-optimization/89689
	* builtins.def (BUILT_IN_OBJECT_SIZE): Make it const rather than pure.

	PR tree-optimization/89689
	* gcc.dg/pr89689.c: New test.

gcc/ChangeLog

+2020-01-24  Jeff Law  <law@redhat.com>
+
+	PR tree-optimization/89689
+	* builtins.def (BUILT_IN_OBJECT_SIZE): Make it const rather than pure.
+
 2020-01-29  Richard Sandiford  <richard.sandiford@arm.com>
 
 	Revert:

gcc/builtins.def

@@ -972,7 +972,7 @@ DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
 DEF_BUILTIN_STUB (BUILT_IN_STRNCMP_EQ, "__builtin_strncmp_eq")
 
 /* Object size checking builtins.  */
-DEF_GCC_BUILTIN	       (BUILT_IN_OBJECT_SIZE, "object_size", BT_FN_SIZE_CONST_PTR_INT, ATTR_PURE_NOTHROW_LEAF_LIST)
+DEF_GCC_BUILTIN	       (BUILT_IN_OBJECT_SIZE, "object_size", BT_FN_SIZE_CONST_PTR_INT, ATTR_CONST_NOTHROW_LEAF_LIST)
 DEF_EXT_LIB_BUILTIN    (BUILT_IN_MEMCPY_CHK, "__memcpy_chk", BT_FN_PTR_PTR_CONST_PTR_SIZE_SIZE, ATTR_RET1_NOTHROW_NONNULL_LEAF)
 DEF_EXT_LIB_BUILTIN    (BUILT_IN_MEMMOVE_CHK, "__memmove_chk", BT_FN_PTR_PTR_CONST_PTR_SIZE_SIZE, ATTR_RET1_NOTHROW_NONNULL_LEAF)
 DEF_EXT_LIB_BUILTIN    (BUILT_IN_MEMPCPY_CHK, "__mempcpy_chk", BT_FN_PTR_PTR_CONST_PTR_SIZE_SIZE, ATTR_RETNONNULL_NOTHROW_LEAF)

gcc/testsuite/ChangeLog

+2020-01-29  Jeff Law  <law@redhat.com
+
+	PR tree-optimization/89689
+	* gcc.dg/pr89689.c: New test.
+
 2020-01-29  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/91754 - Fix template arguments comparison with class NTTP.

gcc/testsuite/gcc.dg/pr89689.c

+/* { dg-do-compile } */
+/* { dg-options "-O2 -Warray-bounds" } */
+
+#include <string.h>
+#include <assert.h>
+#include <stdio.h>
+
+static inline __attribute__((__artificial__)) void *a(char *c, const char *d, long n)
+{
+    return __builtin___memcpy_chk(c, d, n, __builtin_object_size(c, 0));
+}
+typedef struct {
+    char *data;
+    int len;
+} sb_t;
+const char __sb_slop[1];
+static void inline set0(sb_t *c)
+{
+    if (c->data != __sb_slop)
+        c->data[0] = 0;
+    else
+        assert (c->data[0] == 0);
+}
+char buf[5];
+sb_t l = {
+    .data = buf,
+    .len = 0
+};
+void o()
+{
+    char *data = "abcd";
+    sb_t h = l;
+    set0(&h);
+    a(h.data, data, strlen(data));
+    printf("%s\n", h.data);
+    printf("%d\n", h.data == __sb_slop);
+    printf("%d\n", h.data == buf);
+    set0(&h);
+}
+int main(void) {
+    o();
+    return 0;
+}