From f285f7b76916420b5d55a83d53a371ebe257cfb2 Mon Sep 17 00:00:00 2001
From: Zachary Snow <zach@zachjs.com>
Date: Sun, 19 Jul 2020 20:27:09 -0600
Subject: [PATCH] Allow reals as constant function parameters

---
 frontends/ast/simplify.cc  | 14 +++++++++++---
 tests/various/const_func.v | 12 ++++++++++++
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index 00f8c8df6..fda064237 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -3029,7 +3029,7 @@ skip_dynamic_range_lvalue_expansion:;
 			bool all_args_const = true;
 			for (auto child : children) {
 				while (child->simplify(true, false, false, 1, -1, false, true)) { }
-				if (child->type != AST_CONSTANT)
+				if (child->type != AST_CONSTANT && child->type != AST_REALVALUE)
 					all_args_const = false;
 			}
 
@@ -4349,8 +4349,16 @@ AstNode *AstNode::eval_const_function(AstNode *fcall)
 			variables[child->str].val = RTLIL::Const(RTLIL::State::Sx, abs(child->range_left - child->range_right)+1);
 			variables[child->str].offset = min(child->range_left, child->range_right);
 			variables[child->str].is_signed = child->is_signed;
-			if (child->is_input && argidx < fcall->children.size())
-				variables[child->str].val = fcall->children.at(argidx++)->bitsAsConst(variables[child->str].val.bits.size());
+			if (child->is_input && argidx < fcall->children.size()) {
+				int width = variables[child->str].val.bits.size();
+				auto* arg_node = fcall->children.at(argidx++);
+				if (arg_node->type == AST_CONSTANT) {
+					variables[child->str].val = arg_node->bitsAsConst(width);
+				} else {
+					log_assert(arg_node->type == AST_REALVALUE);
+					variables[child->str].val = arg_node->realAsConst(width);
+				}
+			}
 			backup_scope[child->str] = current_scope[child->str];
 			current_scope[child->str] = child;
 			continue;
diff --git a/tests/various/const_func.v b/tests/various/const_func.v
index 76cdc385d..541e63b19 100644
--- a/tests/various/const_func.v
+++ b/tests/various/const_func.v
@@ -53,6 +53,15 @@ module top(out);
         c1, c2, c3, c4,
         d1, d2, d3, d4};
 
+    function signed [31:0] negate;
+        input integer inp;
+        negate = ~inp;
+    endfunction
+    parameter W = 10;
+    parameter X = 3;
+    localparam signed Y = $floor(W / X);
+    localparam signed Z = negate($floor(W / X));
+
 // `define VERIFY
 `ifdef VERIFY
     assert property (a1 == 0);
@@ -71,5 +80,8 @@ module top(out);
     assert property (d2 == 0);
     assert property (d3 == 1);
     assert property (d4 == 1);
+
+    assert property (Y == 3);
+    assert property (Z == ~3);
 `endif
 endmodule