Go patch committed: Permit inlining constants and expression statements

[Ian Lance Taylor]

This patch to the Go frontend permits inlining constant expressions
and expression statements.  This relatively minor change increases the
number of inlinable functions/methods in the standard library from 983
to 2179.  In particular it permits inlining math/bits/RotateLeftNN.
This restores the speed of crypto/sha256 back to what it was before
the update to 1.13beta1.  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 275551)
+++ gcc/go/gofrontend/MERGE     (working copy)
@@ -1,4 +1,4 @@
-c6097f269d2b3dbfd5204cf7e3d0b9f8d7ec2b5e
+5c3f52ffbae7a9bb59bce63cd2cffdd8af8f4a92
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: gcc/go/gofrontend/expressions.cc
===================================================================
--- gcc/go/gofrontend/expressions.cc    (revision 275539)
+++ gcc/go/gofrontend/expressions.cc    (working copy)
@@ -3283,6 +3283,10 @@ class Const_expression : public Expressi
   Bexpression*
   do_get_backend(Translate_context* context);
 
+  int
+  do_inlining_cost() const
+  { return 1; }
+
   // When exporting a reference to a const as part of a const
   // expression, we export the value.  We ignore the fact that it has
   // a name.
Index: gcc/go/gofrontend/statements.cc
===================================================================
--- gcc/go/gofrontend/statements.cc     (revision 275396)
+++ gcc/go/gofrontend/statements.cc     (working copy)
@@ -158,6 +158,10 @@ Statement::import_statement(Import_funct
     return Goto_statement::do_import(ifb, loc);
 
   Expression* lhs = Expression::import_expression(ifb, loc);
+
+  if (ifb->match_c_string(" //"))
+    return Statement::make_statement(lhs, true);
+
   ifb->require_c_string(" = ");
   Expression* rhs = Expression::import_expression(ifb, loc);
   return Statement::make_assignment(lhs, rhs, loc);
@@ -2089,6 +2093,14 @@ Expression_statement::do_may_fall_throug
   return true;
 }
 
+// Export an expression statement.
+
+void
+Expression_statement::do_export_statement(Export_function_body* efb)
+{
+  this->expr_->export_expression(efb);
+}
+
 // Convert to backend representation.
 
 Bstatement*
Index: gcc/go/gofrontend/statements.h
===================================================================
--- gcc/go/gofrontend/statements.h      (revision 275396)
+++ gcc/go/gofrontend/statements.h      (working copy)
@@ -924,6 +924,13 @@ class Expression_statement : public Stat
   bool
   do_may_fall_through() const;
 
+  int
+  do_inlining_cost()
+  { return 0; }
+
+  void
+  do_export_statement(Export_function_body*);
+
   Bstatement*
   do_get_backend(Translate_context* context);