From: Zachary Snow <zach@zachjs.com>
Date: Mon, 7 Dec 2020 20:52:44 +0000 (-0700)
Subject: Allow constant function calls in constant function arguments
X-Git-Tag: working-ls180~154^2
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=186d6df4c3e612667b1eb945ce3e27a92e2cb485;p=yosys.git

Allow constant function calls in constant function arguments
---

diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index fb6623f02..8e205cb76 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -1205,6 +1205,11 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 				current_block = this;
 				current_block_child = children[i];
 			}
+			if (!in_param_here && type == AST_FCALL) {
+				bool recommend_const_eval = false;
+				bool require_const_eval = has_const_only_constructs(recommend_const_eval);
+				in_param_here = recommend_const_eval || require_const_eval;
+			}
 			if ((type == AST_ALWAYS || type == AST_INITIAL) && children[i]->type == AST_BLOCK)
 				current_top_block = children[i];
 			if (i == 0 && child_0_is_self_determined)
diff --git a/tests/various/const_arg_loop.v b/tests/various/const_arg_loop.v
index 3bfff4acd..76cc67abb 100644
--- a/tests/various/const_arg_loop.v
+++ b/tests/various/const_arg_loop.v
@@ -14,6 +14,11 @@ module top;
 		end
 	endfunction
 
+	function automatic [31:0] pass_through;
+		input [31:0] inp;
+		pass_through = inp;
+	endfunction
+
 	function automatic [31:0] operation2;
 		input [4:0] var;
 		input integer num;
@@ -47,6 +52,9 @@ module top;
 	wire [31:0] x1;
 	assign x1 = operation1(A, a);
 
+	wire [31:0] x1b;
+	assign x1b = operation1(pass_through(A), a);
+
 	wire [31:0] x2;
 	assign x2 = operation2(A, a);
 
@@ -58,6 +66,7 @@ module top;
     assert property (a == 2);
     assert property (A == 3);
     assert property (x1 == 16);
+    assert property (x1b == 16);
     assert property (x2 == 4);
     assert property (x3 == 16);
 `endif