Add initial constant evaluation to blocks

BlockExpressions are usually evaluated by create a temporary variable to
hold the result of the tail expression in the correctly. Const expressions
do not have a context of a block so we must fold the value to store it
correctly without the need for temporary variables or a stack. To do this
we can leverage the fact that our constexpr code can fold simple CallExpr's
so in this patch we actually generate an implicit artifical function for
the block but do not add it to the translation unit and we then generate
an artifical CallExpr and pass it to the constant folder system, and then
assign the ConstDecl to this folded value thus reusing all of our existing
BlockExpression code instead of a seperate system.

Fixes #799

1 files changed, 7 insertions, 7 deletions

diff --git a/gcc/rust/backend/rust-compile.cc b/gcc/rust/backend/rust-compile.cc
index b12860d..7208ed0 100644
--- a/gcc/rust/backend/rust-compile.cc
+++ b/gcc/rust/backend/rust-compile.cc
@@ -207,11 +207,11 @@ CompileStructExprField::visit (HIR::StructExprFieldIdentifier &field)
 // Shared methods in compilation
 
 void
-HIRCompileBase::compile_function_body (
-  tree fndecl, std::unique_ptr<HIR::BlockExpr> &function_body,
-  bool has_return_type)
+HIRCompileBase::compile_function_body (tree fndecl,
+				       HIR::BlockExpr &function_body,
+				       bool has_return_type)
 {
-  for (auto &s : function_body->get_statements ())
+  for (auto &s : function_body.get_statements ())
     {
       auto compiled_expr = CompileStmt::Compile (s.get (), ctx);
       if (compiled_expr != nullptr)
@@ -222,12 +222,12 @@ HIRCompileBase::compile_function_body (
 	}
     }
 
-  if (function_body->has_expr ())
+  if (function_body.has_expr ())
     {
       // the previous passes will ensure this is a valid return
       // or a valid trailing expression
       tree compiled_expr
-	= CompileExpr::Compile (function_body->expr.get (), ctx);
+	= CompileExpr::Compile (function_body.expr.get (), ctx);
 
       if (compiled_expr != nullptr)
 	{
@@ -238,7 +238,7 @@ HIRCompileBase::compile_function_body (
 
 	      auto ret = ctx->get_backend ()->return_statement (
 		fndecl, retstmts,
-		function_body->get_final_expr ()->get_locus ());
+		function_body.get_final_expr ()->get_locus ());
 	      ctx->add_statement (ret);
 	    }
 	  else