From 23a79730945f2a0e2cc61a2d6a37281dff4be81d Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Sat, 8 Jun 2013 15:12:08 +0200
Subject: [PATCH] Added support for shifter cells to SAT generator

---
 kernel/satgen.h       | 33 ++++++++++++++++++++++++++-------
 passes/sat/example.v  | 17 +++++++++++++++--
 passes/sat/example.ys |  3 ++-
 3 files changed, 43 insertions(+), 10 deletions(-)

diff --git a/kernel/satgen.h b/kernel/satgen.h
index 90e69ad29..ee2e85d72 100644
--- a/kernel/satgen.h
+++ b/kernel/satgen.h
@@ -51,11 +51,7 @@ struct SatGen
 		this->prefix = prefix;
 	}
 
-	virtual ~SatGen()
-	{
-	}
-
-	virtual std::vector<int> importSigSpec(RTLIL::SigSpec &sig)
+	std::vector<int> importSigSpec(RTLIL::SigSpec &sig)
 	{
 		RTLIL::SigSpec s = sig;
 		sigmap->apply(s);
@@ -93,7 +89,7 @@ struct SatGen
 			vec_y.push_back(ez->literal());
 	}
 
-	virtual bool importCell(RTLIL::Cell *cell)
+	bool importCell(RTLIL::Cell *cell)
 	{
 		if (cell->type == "$_AND_" || cell->type == "$_OR_" || cell->type == "$_XOR_" ||
 				cell->type == "$and" || cell->type == "$or" || cell->type == "$xor" || cell->type == "$xnor" ||
@@ -216,9 +212,32 @@ struct SatGen
 			return true;
 		}
 
-		// Unsupported internal cell types: $shl $shr $sshl $sshr $mul $div $mod $pow
+		if (cell->type == "$shl" || cell->type == "$shr" || cell->type == "$sshl" || cell->type == "$sshr") {
+			std::vector<int> a = importSigSpec(cell->connections.at("\\A"));
+			std::vector<int> b = importSigSpec(cell->connections.at("\\B"));
+			std::vector<int> y = importSigSpec(cell->connections.at("\\Y"));
+			char shift_left = cell->type == "$shl" || cell->type == "$sshl";
+			bool sign_extend = cell->type == "$sshr";
+			while (y.size() < a.size())
+				y.push_back(ez->literal());
+			std::vector<int> tmp = a;
+			for (size_t i = 0; i < b.size(); i++)
+			{
+				std::vector<int> tmp_shifted(tmp.size());
+				for (size_t j = 0; j < tmp.size(); j++) {
+					int idx = j + (1 << i) * (shift_left ? -1 : +1);
+					tmp_shifted.at(j) = (0 <= idx && idx < int(tmp.size())) ? tmp.at(idx) : sign_extend ? tmp.back() : ez->FALSE;
+				}
+				tmp = ez->vec_ite(b.at(i), tmp_shifted, tmp);
+			}
+			ez->assume(ez->vec_eq(tmp, y));
+			return true;
+		}
+
+		// Unsupported internal cell types: $mul $div $mod $pow
 		return false;
 	}
 };
 
 #endif
+
diff --git a/passes/sat/example.v b/passes/sat/example.v
index 9e8c94b73..aa0ddb6e3 100644
--- a/passes/sat/example.v
+++ b/passes/sat/example.v
@@ -51,7 +51,20 @@ endmodule
 
 // ------------------------------------
 
-module example003(clk, rst, y);
+module example003(a_shl, a_shr, a_sshl, a_sshr, sh, y_shl, y_shr, y_sshl, y_sshr);
+
+input [7:0] a_shl, a_shr;
+input signed [7:0] a_sshl, a_sshr;
+input [3:0] sh;
+
+output [7:0] y_shl = a_shl << sh, y_shr = a_shr >> sh;
+output signed [7:0] y_sshl = a_sshl <<< sh, y_sshr = a_sshr >>> sh;
+
+endmodule
+
+// ------------------------------------
+
+module example004(clk, rst, y);
 
 input clk, rst;
 output y;
@@ -59,7 +72,7 @@ output y;
 reg [3:0] counter;
 
 always @(posedge clk)
-	case (1)
+	case (1'b1)
 		rst, counter == 9:
 			counter <= 0;
 		default:
diff --git a/passes/sat/example.ys b/passes/sat/example.ys
index d4037f781..3de8c7997 100644
--- a/passes/sat/example.ys
+++ b/passes/sat/example.ys
@@ -2,4 +2,5 @@ read_verilog example.v
 proc; opt_clean
 sat_solve -set y 1'b1 example001
 sat_solve -set y 1'b1 example002
-sat_solve -set y 1'b1 example003
+sat_solve -set y_sshl 8'hf0 -set y_sshr 8'hf0 -set sh 4'd3 example003
+sat_solve -set y 1'b1 example004