From 8fe2211e2bc8fd21a07c823ffd2c5ebcd6219280 Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Thu, 12 Jun 2008 11:24:43 +0100
Subject: [PATCH] Generate `after' modifier instead of `wait' statements

---
 tgt-vhdl/stmt.cc        | 37 ++++++++++++++++++++++++++-----------
 tgt-vhdl/vhdl_syntax.cc | 15 +++++++++++++++
 tgt-vhdl/vhdl_syntax.hh |  6 ++++--
 3 files changed, 45 insertions(+), 13 deletions(-)

diff --git a/tgt-vhdl/stmt.cc b/tgt-vhdl/stmt.cc
index c22d20777..6a2076e5f 100644
--- a/tgt-vhdl/stmt.cc
+++ b/tgt-vhdl/stmt.cc
@@ -171,7 +171,7 @@ static int draw_noop(vhdl_process *proc, stmt_container *container,
  * assignment.
  */
 static int draw_nbassign(vhdl_process *proc, stmt_container *container,
-                         ivl_statement_t stmt)
+                         ivl_statement_t stmt, vhdl_expr *after = NULL)
 {
    int nlvals = ivl_stmt_lvals(stmt);
    if (nlvals != 1) {
@@ -195,7 +195,10 @@ static int draw_nbassign(vhdl_process *proc, stmt_container *container,
       // The type here can be null as it is never actually needed
       vhdl_var_ref *lval_ref = new vhdl_var_ref(signame, NULL);
 
-      container->add_stmt(new vhdl_nbassign_stmt(lval_ref, rhs));
+      vhdl_nbassign_stmt *nbassign = new vhdl_nbassign_stmt(lval_ref, rhs);
+      if (after != NULL)
+         nbassign->set_after(after);
+      container->add_stmt(nbassign);
    }
    else {
       error("Only signals as lvals supported at the moment");
@@ -221,16 +224,28 @@ static int draw_delay(vhdl_process *proc, stmt_container *container,
    // VHDL wait statement compute the value from that.
    // The other solution is to add them as parameters to
    // the vhdl_process class
-   vhdl_wait_stmt *wait =
-      new vhdl_wait_stmt(VHDL_WAIT_FOR_NS, new vhdl_const_int(value));
-   container->add_stmt(wait);
-   
-   // Expand the sub-statement as well
-   // Often this would result in a useless `null' statement which
-   // is caught here instead
+   vhdl_expr *time = new vhdl_const_int(value);
+
+   // If the sub-statement is an assignment then VHDL lets
+   // us put the delay after it, which is more compact and
+   // idiomatic
    ivl_statement_t sub_stmt = ivl_stmt_sub_stmt(stmt);
-   if (ivl_statement_type(sub_stmt) != IVL_ST_NOOP)
-      draw_stmt(proc, container, sub_stmt);
+   ivl_statement_type_t type = ivl_statement_type(sub_stmt);
+   if (type == IVL_ST_ASSIGN_NB) {
+      draw_nbassign(proc, container, sub_stmt, time);
+   }
+   else {
+      vhdl_wait_stmt *wait =
+         new vhdl_wait_stmt(VHDL_WAIT_FOR_NS, time);
+      container->add_stmt(wait);
+
+      // Expand the sub-statement as well
+      // Often this would result in a useless `null' statement which
+      // is caught here instead
+      if (ivl_statement_type(sub_stmt) != IVL_ST_NOOP)
+         draw_stmt(proc, container, sub_stmt);
+   
+   }
    
    return 0;
 }
diff --git a/tgt-vhdl/vhdl_syntax.cc b/tgt-vhdl/vhdl_syntax.cc
index 2145c5874..ae8dc2595 100644
--- a/tgt-vhdl/vhdl_syntax.cc
+++ b/tgt-vhdl/vhdl_syntax.cc
@@ -484,11 +484,26 @@ void vhdl_fcall::emit(std::ofstream &of, int level) const
    exprs_.emit(of, level);
 }
 
+vhdl_nbassign_stmt::~vhdl_nbassign_stmt()
+{
+   delete lhs_;
+   delete rhs_;
+   if (after_)
+      delete after_;
+}
+
 void vhdl_nbassign_stmt::emit(std::ofstream &of, int level) const
 {
    lhs_->emit(of, level);
    of << " <= ";
    rhs_->emit(of, level);
+
+   if (after_) {
+      of << " after ";
+      after_->emit(of, level);
+      of << " ns";
+   }
+   
    of << ";";
 }
 
diff --git a/tgt-vhdl/vhdl_syntax.hh b/tgt-vhdl/vhdl_syntax.hh
index 191eb56bb..52b7aee69 100644
--- a/tgt-vhdl/vhdl_syntax.hh
+++ b/tgt-vhdl/vhdl_syntax.hh
@@ -226,12 +226,14 @@ private:
 class vhdl_nbassign_stmt : public vhdl_seq_stmt {
 public:
    vhdl_nbassign_stmt(vhdl_var_ref *lhs, vhdl_expr *rhs)
-      : lhs_(lhs), rhs_(rhs) {}
+      : lhs_(lhs), rhs_(rhs), after_(NULL) {}
+   ~vhdl_nbassign_stmt();
 
+   void set_after(vhdl_expr *after) { after_ = after; }
    void emit(std::ofstream &of, int level) const;
 private:
    vhdl_var_ref *lhs_;
-   vhdl_expr *rhs_;
+   vhdl_expr *rhs_, *after_;
 };
 
 enum vhdl_wait_type_t {