re PR middle-end/21478 (Improve initialization of sparse local arrays)

        PR 21478
        * gimplify.c (gimplify_init_constructor): Don't spill initializer
        to read-only memory if it's sparse.

From-SVN: r100465

2 files changed, 33 insertions, 24 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 9696305..1531a27 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2005-06-01  Josh Conner <jconner@apple.com>
+
+	PR 21478
+	* gimplify.c (gimplify_init_constructor): Don't spill initializer
+	to read-only memory if it's sparse.
+
 2005-06-01  Ramana Radhakrishnan  <ramana@codito.com>
 
 	* doc/rtl.texi: Remove references to NOTE_INSN_SETJMP. 
diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index 853ff9d..a659e77 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -2649,10 +2649,35 @@ gimplify_init_constructor (tree *expr_p, tree *pre_p,
 	    break;
 	  }
 
+	/* If there are "lots" of initialized elements, even discounting
+	   those that are not address constants (and thus *must* be
+	   computed at runtime), then partition the constructor into
+	   constant and non-constant parts.  Block copy the constant
+	   parts in, then generate code for the non-constant parts.  */
+	/* TODO.  There's code in cp/typeck.c to do this.  */
+
+	num_type_elements = count_type_elements (TREE_TYPE (ctor));
+
+	/* If there are "lots" of zeros, then block clear the object first.  */
+	if (num_type_elements - num_nonzero_elements > CLEAR_RATIO
+	    && num_nonzero_elements < num_type_elements/4)
+	  cleared = true;
+
+	/* ??? This bit ought not be needed.  For any element not present
+	   in the initializer, we should simply set them to zero.  Except
+	   we'd need to *find* the elements that are not present, and that
+	   requires trickery to avoid quadratic compile-time behavior in
+	   large cases or excessive memory use in small cases.  */
+	else if (num_ctor_elements < num_type_elements)
+	  cleared = true;
+
 	/* If there are "lots" of initialized elements, and all of them
 	   are valid address constants, then the entire initializer can
-	   be dropped to memory, and then memcpy'd out.  */
-	if (num_nonconstant_elements == 0)
+	   be dropped to memory, and then memcpy'd out.  Don't do this
+	   for sparse arrays, though, as it's more efficient to follow
+	   the standard CONSTRUCTOR behavior of memset followed by
+	   individual element initialization.  */
+	if (num_nonconstant_elements == 0 && !cleared)
 	  {
 	    HOST_WIDE_INT size = int_size_in_bytes (type);
 	    unsigned int align;
@@ -2698,28 +2723,6 @@ gimplify_init_constructor (tree *expr_p, tree *pre_p,
 	      }
 	  }
 
-	/* If there are "lots" of initialized elements, even discounting
-	   those that are not address constants (and thus *must* be
-	   computed at runtime), then partition the constructor into
-	   constant and non-constant parts.  Block copy the constant
-	   parts in, then generate code for the non-constant parts.  */
-	/* TODO.  There's code in cp/typeck.c to do this.  */
-
-	num_type_elements = count_type_elements (TREE_TYPE (ctor));
-
-	/* If there are "lots" of zeros, then block clear the object first.  */
-	if (num_type_elements - num_nonzero_elements > CLEAR_RATIO
-	    && num_nonzero_elements < num_type_elements/4)
-	  cleared = true;
-
-	/* ??? This bit ought not be needed.  For any element not present
-	   in the initializer, we should simply set them to zero.  Except
-	   we'd need to *find* the elements that are not present, and that
-	   requires trickery to avoid quadratic compile-time behavior in
-	   large cases or excessive memory use in small cases.  */
-	else if (num_ctor_elements < num_type_elements)
-	  cleared = true;
-
 	if (cleared)
 	  {
 	    /* Zap the CONSTRUCTOR element list, which simplifies this case.