invoke.texi (ssa-name-def-chain-limit): Document new --param.

gcc/ChangeLog:

	* doc/invoke.texi (ssa-name-def-chain-limit): Document new --param.
	* params.def (PARAM_SSA_NAME_DEF_CHAIN_LIMIT): Add new --param.
	* tree-vrp.c (vrp_prop::check_mem_ref): Use
	PARAM_SSA_NAME_DEF_CHAIN_LIMIT.

gcc/testsuite/ChangeLog:

	* gcc.dg/Warray-bounds-43.c: New test.

From-SVN: r273454

gcc/ChangeLog

+2019-07-12  Martin Sebor  <msebor@redhat.com>
+
+	* doc/invoke.texi (ssa-name-def-chain-limit): Document new --param.
+	* params.def (PARAM_SSA_NAME_DEF_CHAIN_LIMIT): Add new --param.
+	* tree-vrp.c (vrp_prop::check_mem_ref): Use
+	PARAM_SSA_NAME_DEF_CHAIN_LIMIT.
+
 2019-07-12  Jan Hubicka  <jh@suse.cz>
 
 	* tree-ssa-alias.c (same_tmr_indexing_p): Break out from ...
@@ -28,7 +35,6 @@
 	rather than this_state as the lowering context for the ELSE
 	seq in a GIMPLE_EH_ELSE.
 
->>>>>>> .r273450
 2019-07-12  Richard Sandiford  <richard.sandiford@arm.com>
 
 	* vector-builder.h (vector_builder::elt): Allow already-supplied

gcc/doc/invoke.texi

@@ -12225,6 +12225,13 @@ before the loop versioning pass considers it too big to copy,
 discounting any instructions in inner loops that directly benefit
 from versioning.
 
+@item ssa-name-def-chain-limit
+The maximum number of SSA_NAME assignments to follow in determining
+a property of a variable such as its value.  This limits the number
+of iterations or recursive calls GCC performs when optimizing certain
+statements or when determining their validity prior to issuing
+diagnostics.
+
 @end table
 @end table
 

gcc/params.def

@@ -1437,6 +1437,12 @@ DEFPARAM(PARAM_HASH_TABLE_VERIFICATION_LIMIT,
 	 "each searched element.",
 	 10, 0, 0)
 
+DEFPARAM(PARAM_SSA_NAME_DEF_CHAIN_LIMIT,
+	 "ssa-name-def-chain-limit",
+	 "The maximum number of SSA_NAME assignments to follow in determining "
+	 "a value.",
+	 512, 0, 0)
+
 /*
 
 Local variables:

gcc/testsuite/ChangeLog

+2019-07-12  Martin Sebor  <msebor@redhat.com>
+
+	* gcc.dg/Warray-bounds-43.c: New test.
+
 2019-07-12  Jan Hubicka  <jh@suse.cz>
 
 	* gcc.dg/tree-ssa/alias-access-path-9.c: New testcase.

gcc/testsuite/gcc.dg/Warray-bounds-43.c

+/* Test to verify that --param ssa_name_def_chain_limit can be used to
+   limit the maximum number of SSA_NAME assignments the warning follows.
+   { dg-do compile }
+   { dg-options "-O2 -Wall --param ssa-name-def-chain-limit=4" }  */
+
+#define NOIPA __attribute__ ((noipa))
+
+const char a0[] = "";
+const char a1[] = "1";
+const char a2[] = "12";
+const char a3[] = "123";
+const char a4[] = "1234";
+const char a5[] = "12345";
+const char a6[] = "123456";
+const char a7[] = "1234567";
+const char a8[] = "12345678";
+const char a9[] = "123456789";
+
+void f (const char*, ...);
+
+int i0, i1, i2, i3, i4, i5, i6, i7, i8;
+
+NOIPA int g2 (int i)
+{
+  if (i < 1) i = 1;
+
+  const char *p0 = a9;
+  const char *p1 = p0 + i;
+  const char *p2 = p1 + i;
+
+  f (p0, p1, p2);
+
+  return p2[8];     // { dg-warning "\\\[-Warray-bounds]" }
+}
+
+NOIPA int g3 (int i)
+{
+  if (i < 1) i = 1;
+
+  const char *p0 = a9;
+  const char *p1 = p0 + i;
+  const char *p2 = p1 + i;
+  const char *p3 = p2 + i;
+
+  f (p0, p1, p2, p3);
+
+  return p3[7];     // { dg-warning "\\\[-Warray-bounds]" }
+}
+
+NOIPA int g4 (int i)
+{
+  if (i < 1) i = 1;
+
+  const char *p0 = a9;
+  const char *p1 = p0 + i;
+  const char *p2 = p1 + i;
+  const char *p3 = p2 + i;
+  const char *p4 = p3 + i;
+
+  f (p0, p1, p2, p3, p4);
+
+  return p4[6];     // { dg-warning "\\\[-Warray-bounds]" }
+}
+
+NOIPA int g5 (int i)
+{
+  if (i < 1) i = 1;
+
+  const char *p0 = a9;
+  const char *p1 = p0 + i;
+  const char *p2 = p1 + i;
+  const char *p3 = p2 + i;
+  const char *p4 = p3 + i;
+  const char *p5 = p4 + i;
+
+  f (p0, p1, p2, p3, p4, p5);
+
+  return p5[5];
+}
+
+NOIPA int g6 (int i)
+{
+  if (i < 1) i = 1;
+
+  const char *p0 = a9;
+  const char *p1 = p0 + i;
+  const char *p2 = p1 + i;
+  const char *p3 = p2 + i;
+  const char *p4 = p3 + i;
+  const char *p5 = p4 + i;
+  const char *p6 = p5 + i;
+
+  f (p0, p1, p2, p3, p4, p5, p6);
+
+  return p6[4];
+}
+
+NOIPA int g7 (int i)
+{
+  if (i < 1) i = 1;
+
+  const char *p0 = a9;
+  const char *p1 = p0 + i;
+  const char *p2 = p1 + i;
+  const char *p3 = p2 + i;
+  const char *p4 = p3 + i;
+  const char *p5 = p4 + i;
+  const char *p6 = p5 + i;
+  const char *p7 = p6 + i;
+
+  f (p0, p1, p2, p3, p4, p5, p6, p7);
+
+  return p7[3];
+}
+
+NOIPA int g8 (int i)
+{
+  if (i < 1) i = 1;
+
+  const char *p0 = a9;
+  const char *p1 = p0 + i;
+  const char *p2 = p1 + i;
+  const char *p3 = p2 + i;
+  const char *p4 = p3 + i;
+  const char *p5 = p4 + i;
+  const char *p6 = p5 + i;
+  const char *p7 = p6 + i;
+  const char *p8 = p7 + i;
+
+  f (p0, p1, p2, p3, p4, p5, p6, p7, p8);
+
+  return p8[2];
+}

gcc/tree-vrp.c

@@ -4492,7 +4492,8 @@ vrp_prop::check_mem_ref (location_t location, tree ref,
      The loop computes the range of the final offset for expressions such
      as (A + i0 + ... + iN)[CSTOFF] where i0 through iN are SSA_NAMEs in
      some range.  */
-  while (TREE_CODE (arg) == SSA_NAME)
+  const unsigned limit = PARAM_VALUE (PARAM_SSA_NAME_DEF_CHAIN_LIMIT);
+  for (unsigned n = 0; TREE_CODE (arg) == SSA_NAME && n < limit; ++n)
     {
       gimple *def = SSA_NAME_DEF_STMT (arg);
       if (!is_gimple_assign (def))