Merge #990

990: Add must use attribute support r=philberty a=philberty

This is a port of the CPP front-end nodiscard attribute to be used for
must_use. It contains a patch to clean up how we handle expressions vs
statements and removes more of the GCC abstraction. Its my hope that we
can leverage more and more existing code to get the static analysis where
we want it.

Fixes #856 

Co-authored-by: Philip Herron <philip.herron@embecosm.com>

1 files changed, 10 insertions, 20 deletions

diff --git a/gcc/rust/backend/rust-compile-expr.h b/gcc/rust/backend/rust-compile-expr.h
index 3cc51d4..8aeb703 100644
--- a/gcc/rust/backend/rust-compile-expr.h
+++ b/gcc/rust/backend/rust-compile-expr.h
@@ -169,7 +169,6 @@ public:
 
   void visit (HIR::AssignmentExpr &expr) override
   {
-    fncontext fn = ctx->peek_fn ();
     auto lvalue = CompileExpr::Compile (expr.get_lhs (), ctx);
     auto rvalue = CompileExpr::Compile (expr.get_rhs (), ctx);
 
@@ -191,7 +190,7 @@ public:
 		       expr.get_rhs ()->get_locus ());
 
     tree assignment
-      = ctx->get_backend ()->assignment_statement (fn.fndecl, lvalue, rvalue,
+      = ctx->get_backend ()->assignment_statement (lvalue, rvalue,
 						   expr.get_locus ());
 
     ctx->add_statement (assignment);
@@ -594,9 +593,7 @@ public:
       = CompileBlock::compile (expr.get_loop_block ().get (), ctx, nullptr);
     tree loop_expr
       = ctx->get_backend ()->loop_expression (code_block, expr.get_locus ());
-    tree loop_stmt
-      = ctx->get_backend ()->expression_statement (fnctx.fndecl, loop_expr);
-    ctx->add_statement (loop_stmt);
+    ctx->add_statement (loop_expr);
 
     if (tmp != NULL)
       {
@@ -645,9 +642,7 @@ public:
       = CompileExpr::Compile (expr.get_predicate_expr ().get (), ctx);
     tree exit_expr
       = ctx->get_backend ()->exit_expression (condition, expr.get_locus ());
-    tree break_stmt
-      = ctx->get_backend ()->expression_statement (fnctx.fndecl, exit_expr);
-    ctx->add_statement (break_stmt);
+    ctx->add_statement (exit_expr);
 
     tree code_block_stmt
       = CompileBlock::compile (expr.get_loop_block ().get (), ctx, nullptr);
@@ -659,14 +654,11 @@ public:
 
     tree loop_expr
       = ctx->get_backend ()->loop_expression (loop_block, expr.get_locus ());
-    tree loop_stmt
-      = ctx->get_backend ()->expression_statement (fnctx.fndecl, loop_expr);
-    ctx->add_statement (loop_stmt);
+    ctx->add_statement (loop_expr);
   }
 
   void visit (HIR::BreakExpr &expr) override
   {
-    fncontext fnctx = ctx->peek_fn ();
     if (expr.has_break_expr ())
       {
 	tree compiled_expr
@@ -676,8 +668,10 @@ public:
 	tree result_reference = ctx->get_backend ()->var_expression (
 	  loop_result_holder, expr.get_expr ()->get_locus ());
 
-	tree assignment = ctx->get_backend ()->assignment_statement (
-	  fnctx.fndecl, result_reference, compiled_expr, expr.get_locus ());
+	tree assignment
+	  = ctx->get_backend ()->assignment_statement (result_reference,
+						       compiled_expr,
+						       expr.get_locus ());
 	ctx->add_statement (assignment);
       }
 
@@ -721,9 +715,7 @@ public:
 	tree exit_expr = ctx->get_backend ()->exit_expression (
 	  ctx->get_backend ()->boolean_constant_expression (true),
 	  expr.get_locus ());
-	tree break_stmt
-	  = ctx->get_backend ()->expression_statement (fnctx.fndecl, exit_expr);
-	ctx->add_statement (break_stmt);
+	ctx->add_statement (exit_expr);
       }
   }
 
@@ -761,9 +753,7 @@ public:
 	  }
       }
 
-    tree goto_label
-      = ctx->get_backend ()->goto_statement (label, expr.get_locus ());
-    ctx->add_statement (goto_label);
+    translated = ctx->get_backend ()->goto_statement (label, expr.get_locus ());
   }
 
   void visit (HIR::BorrowExpr &expr) override;