Re: [PATCH] Optimize var = STRING_CST

[Jakub Jelinek <jakub@redhat.com>]

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On Fri, Aug 24, 2007 at 11:37:25AM +0200, Richard Guenther wrote:
> This is ok if you add a testcase.

Thanks, attached patch is what I have committed.

>  I also bet we have a PR  somewhere for this one...

PR31150 is related, but this patch is just a very partial improvement
for that case and only on some arches (e.g. both ppc32 and ppc64
won't use store_by_pieces on the testcase below for neither
foo nor bar function).


	Jakub

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2007-08-24  Jakub Jelinek  <jakub@redhat.com>

	* expr.c (store_expr): Optimize initialization of an array
	with STRING_CST.
	* expr.h (builtin_strncpy_read_str): New prototype.
	* builtins.c (builtin_strncpy_read_str): Remove prototype.
	No longer static.

	* gcc.dg/array-init-1.c: New test.

--- gcc/builtins.c.jj	2007-08-23 23:31:24.000000000 +0200
+++ gcc/builtins.c	2007-08-23 23:38:22.000000000 +0200
@@ -125,7 +125,6 @@ static rtx expand_builtin_bcopy (tree, i
 static rtx expand_builtin_strcpy (tree, tree, rtx, enum machine_mode);
 static rtx expand_builtin_strcpy_args (tree, tree, tree, rtx, enum machine_mode);
 static rtx expand_builtin_stpcpy (tree, rtx, enum machine_mode);
-static rtx builtin_strncpy_read_str (void *, HOST_WIDE_INT, enum machine_mode);
 static rtx expand_builtin_strncpy (tree, rtx, enum machine_mode);
 static rtx builtin_memset_gen_str (void *, HOST_WIDE_INT, enum machine_mode);
 static rtx expand_builtin_memset (tree, rtx, enum machine_mode);
@@ -3734,7 +3733,7 @@ expand_builtin_stpcpy (tree exp, rtx tar
    bytes from constant string DATA + OFFSET and return it as target
    constant.  */
 
-static rtx
+rtx
 builtin_strncpy_read_str (void *data, HOST_WIDE_INT offset,
 			  enum machine_mode mode)
 {
--- gcc/expr.h.jj	2007-08-23 23:31:24.000000000 +0200
+++ gcc/expr.h	2007-08-23 23:38:22.000000000 +0200
@@ -341,6 +341,7 @@ extern void expand_builtin_setjmp_setup 
 extern void expand_builtin_setjmp_receiver (rtx);
 extern rtx expand_builtin_saveregs (void);
 extern void expand_builtin_trap (void);
+extern rtx builtin_strncpy_read_str (void *, HOST_WIDE_INT, enum machine_mode);
 \f
 /* Functions from expr.c:  */
 
--- gcc/expr.c.jj	2007-08-23 23:31:02.000000000 +0200
+++ gcc/expr.c	2007-08-23 23:38:22.000000000 +0200
@@ -4472,10 +4472,52 @@ store_expr (tree exp, rtx target, int ca
 
       return NULL_RTX;
     }
+  else if (TREE_CODE (exp) == STRING_CST
+	   && !nontemporal && !call_param_p
+	   && TREE_STRING_LENGTH (exp) > 0
+	   && TYPE_MODE (TREE_TYPE (exp)) == BLKmode)
+    {
+      /* Optimize initialization of an array with a STRING_CST.  */
+      HOST_WIDE_INT exp_len, str_copy_len;
+      rtx dest_mem;
+
+      exp_len = int_expr_size (exp);
+      if (exp_len <= 0)
+	goto normal_expr;
+
+      str_copy_len = strlen (TREE_STRING_POINTER (exp));
+      if (str_copy_len < TREE_STRING_LENGTH (exp) - 1)
+	goto normal_expr;
+
+      str_copy_len = TREE_STRING_LENGTH (exp);
+      if ((STORE_MAX_PIECES & (STORE_MAX_PIECES - 1)) == 0)
+	{
+	  str_copy_len += STORE_MAX_PIECES - 1;
+	  str_copy_len &= ~(STORE_MAX_PIECES - 1);
+	}
+      str_copy_len = MIN (str_copy_len, exp_len);
+      if (!can_store_by_pieces (str_copy_len, builtin_strncpy_read_str,
+				(void *) TREE_STRING_POINTER (exp),
+				MEM_ALIGN (target)))
+	goto normal_expr;
+
+      dest_mem = target;
+
+      dest_mem = store_by_pieces (dest_mem,
+				  str_copy_len, builtin_strncpy_read_str,
+				  (void *) TREE_STRING_POINTER (exp),
+				  MEM_ALIGN (target),
+				  exp_len > str_copy_len ? 1 : 0);
+      if (exp_len > str_copy_len)
+	clear_storage (dest_mem, GEN_INT (exp_len - str_copy_len),
+		       BLOCK_OP_NORMAL);
+      return NULL_RTX;
+    }
   else
     {
       rtx tmp_target;
 
+  normal_expr:
       /* If we want to use a nontemporal store, force the value to
 	 register first.  */
       tmp_target = nontemporal ? NULL_RTX : target;
--- gcc/testsuite/gcc.dg/array-init-1.c.jj	2007-08-24 14:12:19.000000000 +0200
+++ gcc/testsuite/gcc.dg/array-init-1.c	2007-08-24 14:22:50.000000000 +0200
@@ -0,0 +1,24 @@
+/* Test that both arrays are initialized by store_by_pieces.  */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+struct A { char c[10]; };
+extern void baz (struct A *);
+
+void
+foo (void)
+{
+  struct A a = { "abcdefghi" };
+  baz (&a);
+}
+
+void
+bar (void)
+{
+  struct A a;
+  __builtin_strcpy (&a.c[0], "abcdefghi");
+  baz (&a);
+}
+
+/* { dg-final { scan-assembler-not "abcdefghi" { target i?86-*-* x86_64-*-* ia64-*-* } } } */
+/* { dg-final { scan-assembler-times "7523094288207667809\|6867666564636261\|1684234849\|64636261" 2 { target i?86-*-* x86_64-*-* ia64-*-* } } } */