From 467141184aa274126ff7e2a41d08bb621b7a3fdf Mon Sep 17 00:00:00 2001
From: Philip Herron <philip.herron@embecosm.com>
Date: Thu, 24 Dec 2020 21:26:26 +0000
Subject: Implement constant expressions

---
 gcc/rust/backend/rust-compile-context.h | 16 ++++++++++++++++
 gcc/rust/backend/rust-compile-expr.h    |  5 +++++
 gcc/rust/backend/rust-compile-item.h    | 19 +++++++++++++++++++
 3 files changed, 40 insertions(+)

(limited to 'gcc/rust/backend')

diff --git a/gcc/rust/backend/rust-compile-context.h b/gcc/rust/backend/rust-compile-context.h
index 5736bf2..288dbda 100644
--- a/gcc/rust/backend/rust-compile-context.h
+++ b/gcc/rust/backend/rust-compile-context.h
@@ -141,6 +141,21 @@ public:
     return true;
   }
 
+  void insert_const_decl (HirId id, ::Bexpression *expr)
+  {
+    compiled_consts[id] = expr;
+  }
+
+  bool lookup_const_decl (HirId id, ::Bexpression **expr)
+  {
+    auto it = compiled_consts.find (id);
+    if (it == compiled_consts.end ())
+      return false;
+
+    *expr = it->second;
+    return true;
+  }
+
   void push_fn (::Bfunction *fn, ::Bvariable *ret_addr)
   {
     fn_stack.push_back (fncontext{fn, ret_addr});
@@ -183,6 +198,7 @@ private:
   std::map<HirId, ::Bvariable *> compiled_var_decls;
   std::map<HirId, ::Btype *> compiled_type_map;
   std::map<HirId, ::Bfunction *> compiled_fn_map;
+  std::map<HirId, ::Bexpression *> compiled_consts;
   std::vector< ::std::vector<Bstatement *> > statements;
   std::vector< ::Bblock *> scope_stack;
 
diff --git a/gcc/rust/backend/rust-compile-expr.h b/gcc/rust/backend/rust-compile-expr.h
index 5c3206a..871b4ba 100644
--- a/gcc/rust/backend/rust-compile-expr.h
+++ b/gcc/rust/backend/rust-compile-expr.h
@@ -105,6 +105,11 @@ public:
 	return;
       }
 
+    // this could be a constant reference
+    if (ctx->lookup_const_decl (ref, &translated))
+      return;
+
+    // must be an identifier
     Bvariable *var = nullptr;
     if (!ctx->lookup_var_decl (ref, &var))
       {
diff --git a/gcc/rust/backend/rust-compile-item.h b/gcc/rust/backend/rust-compile-item.h
index f131a89..10bdce0 100644
--- a/gcc/rust/backend/rust-compile-item.h
+++ b/gcc/rust/backend/rust-compile-item.h
@@ -23,6 +23,7 @@
 #include "rust-compile-tyty.h"
 #include "rust-compile-var-decl.h"
 #include "rust-compile-stmt.h"
+#include "rust-compile-expr.h"
 
 namespace Rust {
 namespace Compile {
@@ -38,6 +39,24 @@ public:
 
   virtual ~CompileItem () {}
 
+  void visit (HIR::ConstantItem &constant)
+  {
+    TyTy::TyBase *resolved_type = nullptr;
+    bool ok
+      = ctx->get_tyctx ()->lookup_type (constant.get_mappings ().get_hirid (),
+					&resolved_type);
+    rust_assert (ok);
+
+    ::Btype *type = TyTyResolveCompile::compile (ctx, resolved_type);
+    Bexpression *value = CompileExpr::Compile (constant.get_expr (), ctx);
+
+    Bexpression *const_expr = ctx->get_backend ()->named_constant_expression (
+      type, constant.get_identifier (), value, constant.get_locus ());
+
+    ctx->push_const (const_expr);
+    ctx->insert_const_decl (constant.get_mappings ().get_hirid (), const_expr);
+  }
+
   void visit (HIR::Function &function)
   {
     // items can be forward compiled which means we may not need to invoke this
-- 
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