From: Roger Sayle <roger@eyesopen.com>
Date: Fri, 22 Dec 2006 03:56:43 +0000 (+0000)
Subject: trans-array.c (gfc_trans_create_temp_array): When the size is known at compile-time... 
X-Git-Tag: releases/gcc-4.3.0~7859
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=fcac92297367e6274fad4392fc8a183076920943;p=thirdparty%2Fgcc.git

trans-array.c (gfc_trans_create_temp_array): When the size is known at compile-time, avoid an unnecessary conditional assignment.


	* trans-array.c (gfc_trans_create_temp_array): When the size is known
	at compile-time, avoid an unnecessary conditional assignment.
	(gfc_array_init_size): Likewise.

From-SVN: r120141
---

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index a7ae44b91699..d25f5bf15234 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,9 @@
+2006-12-21  Roger Sayle  <roger@eyesopen.com>
+
+	* trans-array.c (gfc_trans_create_temp_array): When the size is known
+	at compile-time, avoid an unnecessary conditional assignment.
+	(gfc_array_init_size): Likewise.
+
 2006-12-22  Kazu Hirata  <kazu@codesourcery.com>
 
 	* interface.c: Fix a comment typo.
diff --git a/gcc/fortran/trans-array.c b/gcc/fortran/trans-array.c
index 6201c4c05618..56e69a3d4350 100644
--- a/gcc/fortran/trans-array.c
+++ b/gcc/fortran/trans-array.c
@@ -701,24 +701,33 @@ gfc_trans_create_temp_array (stmtblock_t * pre, stmtblock_t * post,
     {
       if (function)
 	{
-	  var = gfc_create_var (TREE_TYPE (size), "size");
-	  gfc_start_block (&thenblock);
-	  gfc_add_modify_expr (&thenblock, var, gfc_index_zero_node);
-	  thencase = gfc_finish_block (&thenblock);
-
-	  gfc_start_block (&elseblock);
-	  gfc_add_modify_expr (&elseblock, var, size);
-	  elsecase = gfc_finish_block (&elseblock);
+	  /* If we know at compile-time whether any dimension size is
+	     negative, we can avoid a conditional and pass the true size
+	     to gfc_trans_allocate_array_storage, which can then decide
+	     whether to allocate this on the heap or on the stack.  */
+	  if (integer_zerop (or_expr))
+	    ;
+	  else if (integer_onep (or_expr))
+	    size = gfc_index_zero_node;
+	  else
+	    {
+	      var = gfc_create_var (TREE_TYPE (size), "size");
+	      gfc_start_block (&thenblock);
+	      gfc_add_modify_expr (&thenblock, var, gfc_index_zero_node);
+	      thencase = gfc_finish_block (&thenblock);
+
+	      gfc_start_block (&elseblock);
+	      gfc_add_modify_expr (&elseblock, var, size);
+	      elsecase = gfc_finish_block (&elseblock);
 	  
-	  tmp = gfc_evaluate_now (or_expr, pre);
-	  tmp = build3_v (COND_EXPR, tmp, thencase, elsecase);
-	  gfc_add_expr_to_block (pre, tmp);
-	  nelem = var;
-	  size = var;
+	      tmp = gfc_evaluate_now (or_expr, pre);
+	      tmp = build3_v (COND_EXPR, tmp, thencase, elsecase);
+	      gfc_add_expr_to_block (pre, tmp);
+	      size = var;
+	    }
 	}
-      else
-	  nelem = size;
 
+      nelem = size;
       size = fold_build2 (MULT_EXPR, gfc_array_index_type, size,
 			  TYPE_SIZE_UNIT (gfc_get_element_type (type)));
     }
@@ -3275,6 +3284,11 @@ gfc_array_init_size (tree descriptor, int rank, tree * poffset,
       *poffset = offset;
     }
 
+  if (integer_zerop (or_expr))
+    return size;
+  if (integer_onep (or_expr))
+    return gfc_index_zero_node;
+
   var = gfc_create_var (TREE_TYPE (size), "size");
   gfc_start_block (&thenblock);
   gfc_add_modify_expr (&thenblock, var, gfc_index_zero_node);