combine lhs zero_extract fix (PR78186)

	PR rtl-optimization/78186
	* combine.c (change_zero_ext): Mask the RHS of a zero_extract as
	well, when converting to IOR.

From-SVN: r241824

gcc/ChangeLog

+2016-11-03  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR rtl-optimization/78186
+	* combine.c (change_zero_ext): Mask the RHS of a zero_extract as
+	well, when converting to IOR.
+
 2016-11-03  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* config/sparc/sparc.md (vec_interleave_lowv8qi): Delete.

gcc/combine.c

@@ -11190,6 +11190,9 @@ change_zero_ext (rtx pat)
       rtx x = gen_rtx_AND (mode, reg, immed_wide_int_const (mask, mode));
       rtx y = simplify_gen_binary (ASHIFT, mode, SET_SRC (pat),
 				   GEN_INT (offset));
+      wide_int mask2 = wi::shifted_mask (offset, width, false, reg_width);
+      y = simplify_gen_binary (AND, mode, y,
+			       immed_wide_int_const (mask2, mode));
       rtx z = simplify_gen_binary (IOR, mode, x, y);
       SUBST (SET_DEST (pat), reg);
       SUBST (SET_SRC (pat), z);