From cc7187c1725ea09855e3a9002e7b32f8f4424576 Mon Sep 17 00:00:00 2001
From: Stephen Williams <steve@icarus.com>
Date: Sun, 4 May 2008 22:00:01 -0700
Subject: [PATCH] Add support for abs() in logic threads.

Add the code generator code to handle the abs() function in signed
logic. Handle some of the interesting special cases as well.
---
 tgt-stub/expression.c | 26 +++++++++++++++++++++++---
 tgt-vvp/eval_expr.c   | 26 ++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/tgt-stub/expression.c b/tgt-stub/expression.c
index 2de7b787e..fe197c30a 100644
--- a/tgt-stub/expression.c
+++ b/tgt-stub/expression.c
@@ -160,6 +160,28 @@ static void show_ternary_expression(ivl_expr_t net, unsigned ind)
       }
 }
 
+void show_unary_expression(ivl_expr_t net, unsigned ind)
+{
+      unsigned width = ivl_expr_width(net);
+      const char*sign = ivl_expr_signed(net)? "signed" : "unsigned";
+      const char*vt = vt_type_string(net);
+
+      char name[8];
+      switch (ivl_expr_opcode(net)) {
+	  default:
+	    snprintf(name, sizeof name, "%c", ivl_expr_opcode(net));
+	    break;
+
+	  case 'm':
+	    snprintf(name, sizeof name, "abs()");
+	    break;
+      }
+
+      fprintf(out, "%*s<unary \"%s\" width=%u, %s, type=%s>\n", ind, "",
+	      name, width, sign, vt);
+      show_expression(ivl_expr_oper1(net), ind+4);
+}
+
 void show_expression(ivl_expr_t net, unsigned ind)
 {
       unsigned idx;
@@ -252,9 +274,7 @@ void show_expression(ivl_expr_t net, unsigned ind)
 	    break;
 
 	  case IVL_EX_UNARY:
-	    fprintf(out, "%*s<unary \"%c\" width=%u, %s, type=%s>\n", ind, "",
-		    ivl_expr_opcode(net), width, sign, vt);
-	    show_expression(ivl_expr_oper1(net), ind+4);
+	    show_unary_expression(net, ind);
 	    break;
 
 	  case IVL_EX_UFUNC:
diff --git a/tgt-vvp/eval_expr.c b/tgt-vvp/eval_expr.c
index 04848e572..bca49cc0a 100644
--- a/tgt-vvp/eval_expr.c
+++ b/tgt-vvp/eval_expr.c
@@ -2456,6 +2456,32 @@ static struct vector_info draw_unary_expr(ivl_expr_t exp, unsigned wid)
 	    }
 	    break;
 
+	  case 'm': /* abs() */
+	    res = draw_eval_expr_wid(sub, wid, 0);
+
+	    if (!ivl_expr_signed(sub))
+		  break;
+
+	    if (res.base == 0 || res.base == 2 || res.base == 3)
+		  break;
+
+	      /* Handle the special case of a -1 constant. Make the
+	         result a 1. */
+	    if (res.base == 1) {
+		  res.base = allocate_vector(wid);
+		  fprintf(vvp_out, "   %%movi %d, 1, %u;\n",
+			  res.base, res.wid);
+		  break;
+	    }
+
+	    fprintf(vvp_out, "   %%cmpi/s %d, 0, %u;\n", res.base, res.wid);
+	    fprintf(vvp_out, "   %%jmp/0xz T_%u.%u, 5;\n", thread_count, local_count);
+	    fprintf(vvp_out, "   %%inv %d, %u;\n", res.base, res.wid);
+	    fprintf(vvp_out, "   %%addi %d, 1, %u;\n", res.base, res.wid);
+	    fprintf(vvp_out, "T_%u.%u ;\n", thread_count, local_count);
+	    local_count += 1;
+	    break;
+
 	  default:
 	    fprintf(stderr, "vvp error: unhandled unary: %c\n",
 		    ivl_expr_opcode(exp));