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[Patch, fortran] Use memcmp for string comparisons a bit more


Am 29.03.2013 15:56, schrieb Tobias Burnus:

Thus, how about using memcmp for kind=4 for == and /= only - and for
kind=1 also for <, > etc.?

OK, there is the updated patch.

2013-03-25  Thomas Koenig  <tkoenig@gcc.gnu.org>

        * trans-expr.c (build_memcmp_call):  New function.
        (gfc_build_compare_string):  If the strings
        compared have constant and equal lengths and
        the strings are kind=1, or (for kind=4) strings,
        the test is for (in)equality, use memcmp().

2013-03-25  Thomas Koenig  <tkoenig@gcc.gnu.org>

        * gfortran.dg/character_comparison_3.f90:  Adjust for use of memcmp
        for constant and equal string lengths.
        * gfortran.dg/character_comparison_5.f90:  Likewise.
        * gfortran.dg/character_comparison_9.f90:  New test.

Regerssion-tested.  OK for trunk?

	Thomas
Index: fortran/trans-expr.c
===================================================================
--- fortran/trans-expr.c	(Revision 197233)
+++ fortran/trans-expr.c	(Arbeitskopie)
@@ -2665,6 +2665,32 @@
   return -1;
 }
 
+/* Helper to build a call to memcmp.  */
+
+static tree
+build_memcmp_call (tree s1, tree s2, tree n)
+{
+  tree tmp;
+
+  if (!POINTER_TYPE_P (TREE_TYPE (s1)))
+    s1 = gfc_build_addr_expr (pvoid_type_node, s1);
+  else
+    s1 = fold_convert (pvoid_type_node, s1);
+
+  if (!POINTER_TYPE_P (TREE_TYPE (s2)))
+    s2 = gfc_build_addr_expr (pvoid_type_node, s2);
+  else
+    s2 = fold_convert (pvoid_type_node, s2);
+
+  n = fold_convert (size_type_node, n);
+
+  tmp = build_call_expr_loc (input_location,
+			     builtin_decl_explicit (BUILT_IN_MEMCMP),
+			     3, s1, s2, n);
+
+  return fold_convert (integer_type_node, tmp);
+}
+
 /* Compare two strings. If they are all single characters, the result is the
    subtraction of them. Otherwise, we build a library call.  */
 
@@ -2706,6 +2732,26 @@
 	return integer_one_node;
     }
 
+  /* We can compare via memcpy if the strings are known to be equal
+     in length and they are
+     - kind=1
+     - kind=4 and the comparision is for (in)equality.  */
+
+  if (INTEGER_CST_P (len1) && INTEGER_CST_P (len2)
+      && tree_int_cst_equal (len1, len2)
+      && (kind == 1 || code == EQ_EXPR || code == NE_EXPR))
+    {
+      tree tmp;
+      tree chartype;
+
+      chartype = gfc_get_char_type (kind);
+      tmp = fold_build2_loc (input_location, MULT_EXPR, TREE_TYPE(len1),
+			     fold_convert (TREE_TYPE(len1),
+					   TYPE_SIZE_UNIT(chartype)),
+			     len1);
+      return build_memcmp_call (str1, str2, tmp);
+    }
+
   /* Build a call for the comparison.  */
   if (kind == 1)
     fndecl = gfor_fndecl_compare_string;
Index: testsuite/gfortran.dg/character_comparison_3.f90
===================================================================
--- testsuite/gfortran.dg/character_comparison_3.f90	(Revision 197233)
+++ testsuite/gfortran.dg/character_comparison_3.f90	(Arbeitskopie)
@@ -25,6 +25,7 @@
   if (c(:k3) == c(:k44)) call abort
 end program main
 
-! { dg-final { scan-tree-dump-times "gfortran_compare_string" 8 "original" } }
+! { dg-final { scan-tree-dump-times "gfortran_compare_string" 6 "original" } }
+! { dg-final { scan-tree-dump-times "__builtin_memcmp" 2 "original" } }
 ! { dg-final { cleanup-tree-dump "original" } }
 
Index: testsuite/gfortran.dg/character_comparison_5.f90
===================================================================
--- testsuite/gfortran.dg/character_comparison_5.f90	(Revision 197233)
+++ testsuite/gfortran.dg/character_comparison_5.f90	(Arbeitskopie)
@@ -16,6 +16,6 @@
 end program main
 
 ! { dg-final { scan-tree-dump-times "gfortran_concat_string" 0 "original" } }
-! { dg-final { scan-tree-dump-times "gfortran_compare_string" 2 "original" } }
+! { dg-final { scan-tree-dump-times "__builtin_memcmp" 2 "original" } }
 ! { dg-final { cleanup-tree-dump "original" } }
 
! { dg-do run }
! { dg-options "-fdump-tree-original" }
program main
  character (len=2) :: a, b
  character (kind=4,len=4) :: c,d
  a = 'ab'
  b = 'aa'
  if (a < b) call abort
  c = 4_"aaaa"
  d = 4_"aaab"
  if (c == d) call abort
  if (c > d) call abort
end program main
! { dg-final { scan-tree-dump-times "_gfortran_compare_string_char4" 1 "original" } }
! { dg-final { scan-tree-dump-times "__builtin_memcmp" 2 "original" } }
! { dg-final { cleanup-tree-dump "original" } }

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