re PR tree-optimization/86034 (wrong code for bit-field manipulation at -Os)

	PR tree-optimization/86034
	* gimple-ssa-store-merging.c (output_merged_store): Convert the RHS to
	the unsigned bitfield type in a bit insertion sequence if it does not
	have a larger precision than the bitfield size.
	(process_store): Also bypass widening conversions for BIT_INSERT_EXPR.

From-SVN: r261128

gcc/ChangeLog

+2018-06-03  Eric Botcazou  <ebotcazou@adacore.com>
+
+	PR tree-optimization/86034
+	* gimple-ssa-store-merging.c (output_merged_store): Convert the RHS to
+	the unsigned bitfield type in a bit insertion sequence if it does not
+	have a larger precision than the bitfield size.
+	(process_store): Also bypass widening conversions for BIT_INSERT_EXPR.
+
 2018-06-03  Kito Cheng  <kito.cheng@gmail.com>
 
 	* config/nds32/nds32-peephole2.md: Add new patterns for code size.

gcc/gimple-ssa-store-merging.c

@@ -3778,7 +3778,14 @@ imm_store_chain_info::output_merged_store (merged_store_group *group)
 		  const HOST_WIDE_INT end_gap
 		    = (try_bitpos + try_size) - (info->bitpos + info->bitsize);
 		  tree tem = info->ops[0].val;
-		  if ((BYTES_BIG_ENDIAN ? start_gap : end_gap) > 0)
+		  if (TYPE_PRECISION (TREE_TYPE (tem)) <= info->bitsize)
+		    {
+		      tree bitfield_type
+			= build_nonstandard_integer_type (info->bitsize,
+							  UNSIGNED);
+		      tem = gimple_convert (&seq, loc, bitfield_type, tem);
+		    }
+		  else if ((BYTES_BIG_ENDIAN ? start_gap : end_gap) > 0)
 		    {
 		      const unsigned HOST_WIDE_INT imask
 			= (HOST_WIDE_INT_1U << info->bitsize) - 1;
@@ -4270,13 +4277,12 @@ pass_store_merging::process_store (gimple *stmt)
 	      || !multiple_p (bitpos, BITS_PER_UNIT))
 	  && const_bitsize <= 64)
 	{
-	  /* Bypass a truncating conversion to the bit-field type.  */
+	  /* Bypass a conversion to the bit-field type.  */
 	  if (is_gimple_assign (def_stmt) && CONVERT_EXPR_CODE_P (rhs_code))
 	    {
 	      tree rhs1 = gimple_assign_rhs1 (def_stmt);
 	      if (TREE_CODE (rhs1) == SSA_NAME
-		  && INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
-		  && const_bitsize <= TYPE_PRECISION (TREE_TYPE (rhs1)))
+		  && INTEGRAL_TYPE_P (TREE_TYPE (rhs1)))
 		rhs = rhs1;
 	    }
 	  rhs_code = BIT_INSERT_EXPR;

gcc/testsuite/ChangeLog

+2018-06-03  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gcc.dg/torture/pr86034.c: New test.
+
 2018-06-03  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/36497

gcc/testsuite/gcc.dg/torture/pr86034.c

+/* PR tree-optimization/86034 */
+/* Testcase by  Zhendong Su  <su@cs.ucdavis.edu> */
+
+/* { dg-do run } */
+
+struct A
+{
+  int b;
+  int c:24;
+  int d:10;
+  int e;
+} f;
+
+int g; 
+
+void h ()
+{
+  struct A i = { 0, 0, -1, 0 };
+L:
+  f = i;
+  i.d = 0;
+  if (g < 0)
+    goto L;
+}
+
+int main (void)
+{
+  h ();
+  if (f.e != 0) 
+    __builtin_abort ();
+  return 0; 
+}