This patch makes expand_builtin_strncmp attempt to expand via cmpstrnsi
even if neither of the string arguments are string constants.
2016-11-16 Aaron Sawdey
* builtins.c (expand_builtin_strncmp): Attempt expansion of strncmp
via cmpstrnsi even if neither string is constant.
--
Aaron Sawdey, Ph.D. acsaw...@linux.vnet.ibm.com
050-2/C113 (507) 253-7520 home: 507/263-0782
IBM Linux Technology Center - PPC ToolchainIndex: gcc/builtins.c
===
--- gcc/builtins.c (revision 242428)
+++ gcc/builtins.c (working copy)
@@ -3918,7 +3918,7 @@
insn_code cmpstrn_icode = direct_optab_handler (cmpstrn_optab, SImode);
if (cmpstrn_icode != CODE_FOR_nothing)
{
-tree len, len1, len2;
+tree len, len1, len2, len3;
rtx arg1_rtx, arg2_rtx, arg3_rtx;
rtx result;
tree fndecl, fn;
@@ -3937,14 +3937,19 @@
if (len2)
len2 = size_binop_loc (loc, PLUS_EXPR, ssize_int (1), len2);
+len3 = fold_convert_loc (loc, sizetype, arg3);
+
/* If we don't have a constant length for the first, use the length
- of the second, if we know it. We don't require a constant for
+ of the second, if we know it. If neither string is constant length,
+ use the given length argument. We don't require a constant for
this case; some cost analysis could be done if both are available
but neither is constant. For now, assume they're equally cheap,
unless one has side effects. If both strings have constant lengths,
use the smaller. */
-if (!len1)
+if (!len1 && !len2)
+ len = len3;
+else if (!len1)
len = len2;
else if (!len2)
len = len1;
@@ -3961,23 +3966,10 @@
else
len = len2;
-/* If both arguments have side effects, we cannot optimize. */
-if (!len || TREE_SIDE_EFFECTS (len))
- return NULL_RTX;
-
-/* The actual new length parameter is MIN(len,arg3). */
-len = fold_build2_loc (loc, MIN_EXPR, TREE_TYPE (len), len,
- fold_convert_loc (loc, TREE_TYPE (len), arg3));
-
-/* If we don't have POINTER_TYPE, call the function. */
-if (arg1_align == 0 || arg2_align == 0)
- return NULL_RTX;
-
-/* Stabilize the arguments in case gen_cmpstrnsi fails. */
-arg1 = builtin_save_expr (arg1);
-arg2 = builtin_save_expr (arg2);
-len = builtin_save_expr (len);
-
+/* If we are not using the given length, we must incorporate it here.
+ The actual new length parameter will be MIN(len,arg3) in this case. */
+if (len != len3)
+ len = fold_build2_loc (loc, MIN_EXPR, TREE_TYPE (len), len, len3);
arg1_rtx = get_memory_rtx (arg1, len);
arg2_rtx = get_memory_rtx (arg2, len);
arg3_rtx = expand_normal (len);
