support repeat loops with constant repeat counts outside of constant functions

frontends/ast/simplify.cc

@@ -1030,7 +1030,26 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 		log_file_error(filename, linenum, "While loops are only allowed in constant functions!\n");
 
 	if (type == AST_REPEAT)
-		log_file_error(filename, linenum, "Repeat loops are only allowed in constant functions!\n");
+	{
+		AstNode *count = children[0];
+		AstNode *body = children[1];
+
+		// eval count expression
+		while (count->simplify(true, false, false, stage, 32, true, false)) { }
+
+		if (count->type != AST_CONSTANT)
+			log_file_error(filename, linenum, "Repeat loops outside must have constant repeat counts!\n");
+
+		// convert to a block with the body repeated n times
+		type = AST_BLOCK;
+		children.clear();
+		for (int i = 0; i < count->bitsAsConst().as_int(); i++)
+			children.insert(children.begin(), body->clone());
+
+		delete count;
+		delete body;
+		did_something = true;
+	}
 
 	// unroll for loops and generate-for blocks
 	if ((type == AST_GENFOR || type == AST_FOR) && children.size() != 0)

tests/sat/counters-repeat.v

@@ -0,0 +1,38 @@
+// coverage for repeat loops outside of constant functions
+
+module counter1(clk, rst, ping);
+	input clk, rst;
+	output ping;
+	reg [31:0] count;
+
+	always @(posedge clk) begin
+		if (rst)
+			count <= 0;
+		else
+			count <= count + 1;
+	end
+
+	assign ping = &count;
+endmodule
+
+module counter2(clk, rst, ping);
+	input clk, rst;
+	output ping;
+	reg [31:0] count;
+
+	integer i;
+	reg carry;
+
+	always @(posedge clk) begin
+		carry = 1;
+		i = 0;
+		repeat (32) begin
+			count[i] <= !rst & (count[i] ^ carry);
+			carry = count[i] & carry;
+			i = i+1;
+		end
+	end
+
+	assign ping = &count;
+endmodule
+

tests/sat/counters-repeat.ys

@@ -0,0 +1,10 @@
+
+read_verilog counters-repeat.v
+proc; opt
+
+expose -shared counter1 counter2
+miter -equiv -make_assert -make_outputs counter1 counter2 miter
+
+cd miter; flatten; opt
+sat -verify -prove-asserts -tempinduct -set-at 1 in_rst 1 -seq 1 -show-inputs -show-outputs
+