re PR rtl-optimization/48037 (Missed optimization: unnecessary register moves)

2011-03-15  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/48037
	* tree-ssa.c (maybe_rewrite_mem_ref_base): Rewrite vector
	selects into BIT_FIELD_REFs.
	(non_rewritable_mem_ref_base): Check if a MEM_REF is a
	vector select.

	* gcc.target/i386/pr48037-1.c: New testcase.

From-SVN: r170986

gcc/ChangeLog

+2011-03-15  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/48037
+	* tree-ssa.c (maybe_rewrite_mem_ref_base): Rewrite vector
+	selects into BIT_FIELD_REFs.
+	(non_rewritable_mem_ref_base): Check if a MEM_REF is a
+	vector select.
+
 2011-03-15  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/48129

gcc/testsuite/ChangeLog

 2011-03-15  Richard Guenther  <rguenther@suse.de>
 
+	PR tree-optimization/48037
+	* gcc.target/i386/pr48037-1.c: New testcase.
+
+2011-03-15  Richard Guenther  <rguenther@suse.de>
+
 	PR tree-optimization/41490
 	* gcc.dg/tree-ssa/ssa-sink-6.c: New testcase.
 	* gcc.dg/tree-ssa/ssa-sink-7.c: Likewise.

gcc/testsuite/gcc.target/i386/pr48037-1.c

+/* { dg-do compile } */
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-O -fno-math-errno" } */
+
+typedef double __m128d __attribute__((vector_size(16)));
+__m128d vsqrt1 (__m128d const x)
+{
+  double const* __restrict__ const y = (double const*)&x;
+  double const a = __builtin_sqrt(y[0]);
+  double const b = __builtin_sqrt(y[1]);
+  return (__m128d) { a, b };
+}
+
+/* Verify we do not spill x to the stack.  */
+/* { dg-final { scan-assembler-not "%rsp" } } */

gcc/tree-ssa.c

@@ -1838,18 +1838,32 @@ maybe_rewrite_mem_ref_base (tree *tp)
     tp = &TREE_OPERAND (*tp, 0);
   if (TREE_CODE (*tp) == MEM_REF
       && TREE_CODE (TREE_OPERAND (*tp, 0)) == ADDR_EXPR
-      && integer_zerop (TREE_OPERAND (*tp, 1))
       && (sym = TREE_OPERAND (TREE_OPERAND (*tp, 0), 0))
       && DECL_P (sym)
       && !TREE_ADDRESSABLE (sym)
       && symbol_marked_for_renaming (sym))
     {
-      if (!useless_type_conversion_p (TREE_TYPE (*tp),
-				      TREE_TYPE (sym)))
-	*tp = build1 (VIEW_CONVERT_EXPR,
-			TREE_TYPE (*tp), sym);
-      else
-	*tp = sym;
+      if (TREE_CODE (TREE_TYPE (sym)) == VECTOR_TYPE
+	  && useless_type_conversion_p (TREE_TYPE (*tp),
+					TREE_TYPE (TREE_TYPE (sym)))
+	  && multiple_of_p (sizetype, TREE_OPERAND (*tp, 1),
+			    TYPE_SIZE_UNIT (TREE_TYPE (*tp))))
+	{
+	  *tp = build3 (BIT_FIELD_REF, TREE_TYPE (*tp), sym, 
+			TYPE_SIZE (TREE_TYPE (*tp)),
+			int_const_binop (MULT_EXPR,
+					 bitsize_int (BITS_PER_UNIT),
+					 TREE_OPERAND (*tp, 1), 0));
+	}
+      else if (integer_zerop (TREE_OPERAND (*tp, 1)))
+	{
+	  if (!useless_type_conversion_p (TREE_TYPE (*tp),
+					  TREE_TYPE (sym)))
+	    *tp = build1 (VIEW_CONVERT_EXPR,
+			  TREE_TYPE (*tp), sym);
+	  else
+	    *tp = sym;
+	}
     }
 }
 
@@ -1869,11 +1883,18 @@ non_rewritable_mem_ref_base (tree ref)
     base = TREE_OPERAND (base, 0);
 
   /* But watch out for MEM_REFs we cannot lower to a
-     VIEW_CONVERT_EXPR.  */
+     VIEW_CONVERT_EXPR or a BIT_FIELD_REF.  */
   if (TREE_CODE (base) == MEM_REF
       && TREE_CODE (TREE_OPERAND (base, 0)) == ADDR_EXPR)
     {
       tree decl = TREE_OPERAND (TREE_OPERAND (base, 0), 0);
+      if (TREE_CODE (TREE_TYPE (decl)) == VECTOR_TYPE
+	  && useless_type_conversion_p (TREE_TYPE (base),
+					TREE_TYPE (TREE_TYPE (decl)))
+	  && double_int_fits_in_uhwi_p (mem_ref_offset (base))
+	  && multiple_of_p (sizetype, TREE_OPERAND (base, 1),
+			    TYPE_SIZE_UNIT (TREE_TYPE (base))))
+	return NULL_TREE;
       if (DECL_P (decl)
 	  && (!integer_zerop (TREE_OPERAND (base, 1))
 	      || (DECL_SIZE (decl)