From d1314d53bd79d9ce07bec11e1b9f67c6c50a1e72 Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Sun, 15 Aug 2010 19:05:27 +0100
Subject: [PATCH] Reduce superflous parens in generated VHDL

Purely cosmetic, replaces output like:

  if (x + foo(x + (2 * y))) then ...

With:

  if x + foo(x + (2 * y)) then ...
---
 tgt-vhdl/vhdl_syntax.cc | 29 ++++++++++++++++++++++-------
 tgt-vhdl/vhdl_syntax.hh |  5 +++++
 2 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/tgt-vhdl/vhdl_syntax.cc b/tgt-vhdl/vhdl_syntax.cc
index 0391b0137..60bd1a412 100644
--- a/tgt-vhdl/vhdl_syntax.cc
+++ b/tgt-vhdl/vhdl_syntax.cc
@@ -767,6 +767,22 @@ void vhdl_if_stmt::emit(std::ostream &of, int level) const
    of << "end if;";
 }
 
+int vhdl_expr::paren_levels(0);
+
+void vhdl_expr::open_parens(std::ostream& of)
+{
+   if (paren_levels++ > 0)
+      of << "(";
+}
+
+void vhdl_expr::close_parens(std::ostream& of)
+{
+   assert(paren_levels > 0);
+   
+   if (--paren_levels > 0)
+      of << ")";
+}
+
 vhdl_unaryop_expr::~vhdl_unaryop_expr()
 {
 
@@ -774,7 +790,8 @@ vhdl_unaryop_expr::~vhdl_unaryop_expr()
 
 void vhdl_unaryop_expr::emit(std::ostream &of, int level) const
 {
-   of << "(";
+   open_parens(of);
+   
    switch (op_) {
    case VHDL_UNARYOP_NOT:
       of << "not ";
@@ -784,7 +801,8 @@ void vhdl_unaryop_expr::emit(std::ostream &of, int level) const
       break;
    }
    operand_->emit(of, level);
-   of << ")";
+
+   close_parens(of);
 }
 
 vhdl_binop_expr::vhdl_binop_expr(vhdl_expr *left, vhdl_binop_t op,
@@ -807,10 +825,7 @@ void vhdl_binop_expr::add_expr(vhdl_expr *e)
 
 void vhdl_binop_expr::emit(std::ostream &of, int level) const
 {
-   // Expressions are fully parenthesised to remove any
-   // ambiguity in the output
-
-   of << "(";
+   open_parens(of);
 
    assert(operands_.size() > 0);
    std::list<vhdl_expr*>::const_iterator it = operands_.begin();
@@ -828,7 +843,7 @@ void vhdl_binop_expr::emit(std::ostream &of, int level) const
       (*it)->emit(of, level);
    }
 
-   of << ")";
+   close_parens(of);
 }
 
 vhdl_bit_spec_expr::~vhdl_bit_spec_expr()
diff --git a/tgt-vhdl/vhdl_syntax.hh b/tgt-vhdl/vhdl_syntax.hh
index 2d792a6a8..8603e7090 100644
--- a/tgt-vhdl/vhdl_syntax.hh
+++ b/tgt-vhdl/vhdl_syntax.hh
@@ -48,7 +48,12 @@ public:
    virtual vhdl_expr *to_std_logic();
    virtual vhdl_expr *to_std_ulogic();
    virtual vhdl_expr *to_vector(vhdl_type_name_t name, int w);
+   
 protected:
+   static void open_parens(ostream& of);
+   static void close_parens(ostream& of);
+   static int paren_levels;
+   
    const vhdl_type *type_;
    bool isconst_;
 };