Go patch committed: Don't use a nil check for the write barrier

[Ian Lance Taylor]

This patch to the Go frontend by Than McIntosh tweaks the recipe for
generating writeBarrier loads to insure that the dereference expr is
marked as not requiring a nil check.  This should fix gcc PR 89368.
Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
to mainline.

Ian

Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE     (revision 268941)
+++ gcc/go/gofrontend/MERGE     (working copy)
@@ -1,4 +1,4 @@
-0563f2d018cdb2cd685c254bac5ceb38396d0a27
+1a74b8a22b2ff7f430729aa87ecb8cea7b5cdd70
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: gcc/go/gofrontend/wb.cc
===================================================================
--- gcc/go/gofrontend/wb.cc     (revision 268923)
+++ gcc/go/gofrontend/wb.cc     (working copy)
@@ -904,7 +904,8 @@ Gogo::check_write_barrier(Block* enclosi
   ref = Expression::make_unary(OPERATOR_AND, ref, loc);
   ref = Expression::make_cast(unsafe_pointer_type, ref, loc);
   ref = Expression::make_cast(puint32_type, ref, loc);
-  ref = Expression::make_unary(OPERATOR_MULT, ref, loc);
+  ref = Expression::make_dereference(ref,
+                                     Expression::NIL_CHECK_NOT_NEEDED, loc);
   Expression* zero = Expression::make_integer_ul(0, ref->type(), loc);
   Expression* cond = Expression::make_binary(OPERATOR_EQEQ, ref, zero, loc);