diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b953cd04d71..c0280874d3c 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2012-01-23  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/51895
+	* tree-sra.c (decide_one_param_reduction): Avoid sub-optimal
+	parameter decomposition into BLKmode components.
+
 2012-01-23  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* tree-ssa-structalias.c (intra_create_variable_infos): Do not create
diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
index 9c2d13875d9..f4146b2acbc 100644
--- a/gcc/tree-sra.c
+++ b/gcc/tree-sra.c
@@ -3914,6 +3914,13 @@ decide_one_param_reduction (struct access *repr)
       if (by_ref && repr->non_addressable)
 	return 0;
 
+      /* Do not decompose a non-BLKmode param in a way that would
+         create BLKmode params.  Especially for by-reference passing
+	 (thus, pointer-type param) this is hardly worthwhile.  */
+      if (DECL_MODE (parm) != BLKmode
+	  && TYPE_MODE (repr->type) == BLKmode)
+	return 0;
+
       if (!by_ref || (!repr->grp_maybe_modified
 		      && !repr->grp_not_necessarilly_dereferenced))
 	total_size += repr->size;