[gfortran,patch] Don't call library function for string copying, take 2

["François-Xavier Coudert" <fxcoudert at gmail dot com>]

:ADDPATCH fortran:

Attached patch is the second take on PR fortran/28163. Instead of
generating calls to libgfortran copy_string, we emit the code
directly. As my previous mails showed, the size impact is minimal
since the code emitted is small. There is a huge (positive)
performance impact of this on at least one of the polyhedron
benchmarks, aermod.

The differences with my first version of the patch are:
 -- I propose to remove the copy_string function from libgfortran,
since it's not used anywhere else
 -- I have finally found the correct way to create a integer constant
of value ' ' (the space character) in the case the host and target
charsets are differents: lang_hooks.to_target_charset

Bootstrapped and regtested on i686-linux. OK for mainline?

FX

Attachment: copy_string2.ChangeLog
Description: Binary data

Index: gcc/fortran/trans-expr.c
===================================================================
--- gcc/fortran/trans-expr.c	(revision 115174)
+++ gcc/fortran/trans-expr.c	(working copy)
@@ -31,6 +31,7 @@
 #include "toplev.h"
 #include "real.h"
 #include "tree-gimple.h"
+#include "langhooks.h"
 #include "flags.h"
 #include "gfortran.h"
 #include "trans.h"
@@ -2196,6 +2197,11 @@
   tree dsc;
   tree ssc;
   tree cond;
+  tree cond2;
+  tree tmp2;
+  tree tmp3;
+  tree tmp4;
+  stmtblock_t tempblock;
 
   /* Deal with single character specially.  */
   dsc = gfc_to_single_character (dlen, dest);
@@ -2206,15 +2212,63 @@
       return;
     }
 
+  /* Do nothing if the destination length is zero.  */
   cond = fold_build2 (GT_EXPR, boolean_type_node, dlen,
 		      build_int_cst (gfc_charlen_type_node, 0));
 
-  tmp = NULL_TREE;
-  tmp = gfc_chainon_list (tmp, dlen);
-  tmp = gfc_chainon_list (tmp, dest);
-  tmp = gfc_chainon_list (tmp, slen);
-  tmp = gfc_chainon_list (tmp, src);
-  tmp = build_function_call_expr (gfor_fndecl_copy_string, tmp);
+  /* The following code was previously in _gfortran_copy_string:
+
+       // The two strings may overlap so we use memmove.
+       void
+       copy_string (GFC_INTEGER_4 destlen, char * dest,
+                    GFC_INTEGER_4 srclen, const char * src)
+       {
+         if (srclen >= destlen)
+           {
+             // This will truncate if too long.
+             memmove (dest, src, destlen);
+           }
+         else
+           {
+             memmove (dest, src, srclen);
+             // Pad with spaces.
+             memset (&dest[srclen], ' ', destlen - srclen);
+           }
+       }
+
+     We're now doing it here for better optimization, but the logic
+     is the same.  */
+  
+  /* Truncate string if source is too long.  */
+  cond2 = fold_build2 (GE_EXPR, boolean_type_node, slen, dlen);
+  tmp2 = gfc_chainon_list (NULL_TREE, dest);
+  tmp2 = gfc_chainon_list (tmp2, src);
+  tmp2 = gfc_chainon_list (tmp2, dlen);
+  tmp2 = build_function_call_expr (built_in_decls[BUILT_IN_MEMMOVE], tmp2);
+
+  /* Else copy and pad with spaces.  */
+  tmp3 = gfc_chainon_list (NULL_TREE, dest);
+  tmp3 = gfc_chainon_list (tmp3, src);
+  tmp3 = gfc_chainon_list (tmp3, slen);
+  tmp3 = build_function_call_expr (built_in_decls[BUILT_IN_MEMMOVE], tmp3);
+
+  tmp4 = fold_build2 (PLUS_EXPR, pchar_type_node, dest,
+		      fold_convert (pchar_type_node, slen));
+  tmp4 = gfc_chainon_list (NULL_TREE, tmp4);
+  tmp4 = gfc_chainon_list (tmp4, build_int_cst
+				   (gfc_get_int_type (gfc_c_int_kind),
+				    lang_hooks.to_target_charset (' ')));
+  tmp4 = gfc_chainon_list (tmp4, fold_build2 (MINUS_EXPR, TREE_TYPE(dlen),
+					      dlen, slen));
+  tmp4 = build_function_call_expr (built_in_decls[BUILT_IN_MEMSET], tmp4);
+
+  gfc_init_block (&tempblock);
+  gfc_add_expr_to_block (&tempblock, tmp3);
+  gfc_add_expr_to_block (&tempblock, tmp4);
+  tmp3 = gfc_finish_block (&tempblock);
+
+  /* The whole copy_string function is there.  */
+  tmp = fold_build3 (COND_EXPR, void_type_node, cond2, tmp2, tmp3);
   tmp = fold_build3 (COND_EXPR, void_type_node, cond, tmp, build_empty_stmt ());
   gfc_add_expr_to_block (block, tmp);
 }
Index: gcc/fortran/trans-decl.c
===================================================================
--- gcc/fortran/trans-decl.c	(revision 115174)
+++ gcc/fortran/trans-decl.c	(working copy)
@@ -121,7 +121,6 @@
 
 /* String functions.  */
 
-tree gfor_fndecl_copy_string;
 tree gfor_fndecl_compare_string;
 tree gfor_fndecl_concat_string;
 tree gfor_fndecl_string_len_trim;
@@ -1938,13 +1937,6 @@
   tree gfc_c_int_type_node = gfc_get_int_type (gfc_c_int_kind);
 
   /* String functions.  */
-  gfor_fndecl_copy_string =
-    gfc_build_library_function_decl (get_identifier (PREFIX("copy_string")),
-				     void_type_node,
-				     4,
-				     gfc_charlen_type_node, pchar_type_node,
-				     gfc_charlen_type_node, pchar_type_node);
-
   gfor_fndecl_compare_string =
     gfc_build_library_function_decl (get_identifier (PREFIX("compare_string")),
 				     gfc_int4_type_node,
Index: gcc/fortran/trans.h
===================================================================
--- gcc/fortran/trans.h	(revision 115174)
+++ gcc/fortran/trans.h	(working copy)
@@ -508,7 +508,6 @@
 extern GTY(()) tree gfor_fndecl_math_exponent16;
 
 /* String functions.  */
-extern GTY(()) tree gfor_fndecl_copy_string;
 extern GTY(()) tree gfor_fndecl_compare_string;
 extern GTY(()) tree gfor_fndecl_concat_string;
 extern GTY(()) tree gfor_fndecl_string_len_trim;
Index: libgfortran/intrinsics/string_intrinsics.c
===================================================================
--- libgfortran/intrinsics/string_intrinsics.c	(revision 115174)
+++ libgfortran/intrinsics/string_intrinsics.c	(working copy)
@@ -44,9 +44,6 @@
 
 /* String functions.  */
 
-extern void copy_string (GFC_INTEGER_4, char *, GFC_INTEGER_4, const char *);
-export_proto(copy_string);
-
 extern void concat_string (GFC_INTEGER_4, char *,
 			   GFC_INTEGER_4, const char *,
 			   GFC_INTEGER_4, const char *);
@@ -79,26 +76,6 @@
 extern void string_repeat (char *, GFC_INTEGER_4, const char *, GFC_INTEGER_4);
 export_proto(string_repeat);
 
-/* The two areas may overlap so we use memmove.  */
-
-void
-copy_string (GFC_INTEGER_4 destlen, char * dest,
-	     GFC_INTEGER_4 srclen, const char * src)
-{
-  if (srclen >= destlen)
-    {
-      /* This will truncate if too long.  */
-      memmove (dest, src, destlen);
-    }
-  else
-    {
-      memmove (dest, src, srclen);
-      /* Pad with spaces.  */
-      memset (&dest[srclen], ' ', destlen - srclen);
-    }
-}
-
-
 /* Strings of unequal length are extended with pad characters.  */
 
 GFC_INTEGER_4