Merge pull request #807 from diffblue/riscv-alu.sv

SystemVerilog: RISC-V ALU test

Author: tautschnig

regression/verilog/case/riscv-alu.desc

@@ -0,0 +1,18 @@
+CORE
+riscv-alu.sv
+--module alu --bound 0
+^\[alu\.pADD\] always alu\.op == \{ 7'b0000000, 3'b000 \} -> alu\.out == alu\.a \+ alu\.b: PROVED up to bound 0$
+^\[alu\.pSUB\] always alu\.op == \{ 7'b0100000, 3'b000 \} -> alu\.out == alu\.a - alu\.b: PROVED up to bound 0$
+^\[alu\.pSLL\] always alu\.op == \{ 7'b0000000, 3'b001 \} -> alu\.out == alu\.a << alu\.b\[4:0\]: PROVED up to bound 0$
+^\[alu\.pSLT\] always alu\.op == \{ 7'b0000000, 3'b010 \} -> alu\.out == alu\.a < alu\.b: PROVED up to bound 0$
+^\[alu\.pSLTU\] always alu\.op == \{ 7'b0000000, 3'b011 \} -> alu\.out == alu\.a < alu\.b: PROVED up to bound 0$
+^\[alu\.pXOR\] always alu\.op == \{ 7'b0000000, 3'b100 \} -> alu\.out == \(alu\.a \^ alu\.b\): PROVED up to bound 0$
+^\[alu\.pSRL\] always alu\.op == \{ 7'b0000000, 3'b101 \} -> alu\.out == alu\.a >> alu\.b\[4:0\]: PROVED up to bound 0$
+^\[alu\.pSRA\] always alu\.op == \{ 7'b0100000, 3'b101 \} -> alu\.out == alu\.a >>> alu\.b\[4:0\]: PROVED up to bound 0$
+^\[alu\.pOR\] always alu\.op == \{ 7'b0000000, 3'b110 \} -> alu\.out == \(alu\.a | alu\.b\): PROVED up to bound 0$
+^\[alu\.pAND\] always alu\.op == \{ 7'b0000000, 3'b111 \} -> alu\.out == \(alu\.a & alu\.b\): PROVED up to bound 0$
+^EXIT=0$
+^SIGNAL=0$
+--
+^warning: ignoring
+--

regression/verilog/case/riscv-alu.sv

@@ -0,0 +1,51 @@
+
+module alu(
+  input [2:0] func3,
+  input [6:0] func7,
+  input [63:0] a, b,
+  output reg [63:0] out);
+
+  // https://riscv.org/wp-content/uploads/2017/05/riscv-spec-v2.2.pdf
+  // Page 104
+  wire ADD  = func7 == 'b0000000 & func3 == 'b000;
+  wire SUB  = func7 == 'b0100000 & func3 == 'b000;
+  wire SLL  = func7 == 'b0000000 & func3 == 'b001;
+  wire SLT  = func7 == 'b0000000 & func3 == 'b010;
+  wire SLTU = func7 == 'b0000000 & func3 == 'b011;
+  wire XOR  = func7 == 'b0000000 & func3 == 'b100;
+  wire SRL  = func7 == 'b0000000 & func3 == 'b101;
+  wire SRA  = func7 == 'b0100000 & func3 == 'b101;
+  wire OR   = func7 == 'b0000000 & func3 == 'b110;
+  wire AND  = func7 == 'b0000000 & func3 == 'b111;
+
+  wire subtraction = SUB || SLT || SLTU;
+  wire [64:0] a_ext = {SLT ? a[63] : 0, a};
+  wire [64:0] b_ext = {SLT ? b[63] : 0, b};
+  wire [64:0] b_inv = (subtraction?~b_ext:b_ext);
+  wire [64:0] adder_out = a_ext + b_inv + subtraction;
+
+  always_comb case(1)
+    ADD || SUB:  out <= adder_out[63:0];
+    SLL:         out <= a << b[4:0];
+    SLT || SLTU: out <= adder_out[64];
+    XOR:         out <= a ^ b;
+    SRL:         out <= a >> b[4:0];
+    SRA:         out <= $signed(a) >>> b[4:0];
+    OR:          out <= a | b;
+    AND:         out <= a & b;
+    default:     out <= 0;
+  endcase
+
+  wire [9:0] op = {func7, func3};
+  pADD:  assert final (op == {7'b0000000, 3'b000} -> out == a + b);
+  pSUB:  assert final (op == {7'b0100000, 3'b000} -> out == a - b);
+  pSLL:  assert final (op == {7'b0000000, 3'b001} -> out == a << b[4:0]);
+  pSLT:  assert final (op == {7'b0000000, 3'b010} -> out == ($signed(a) < $signed(b)));
+  pSLTU: assert final (op == {7'b0000000, 3'b011} -> out == (a < b));
+  pXOR:  assert final (op == {7'b0000000, 3'b100} -> out == (a ^ b));
+  pSRL:  assert final (op == {7'b0000000, 3'b101} -> out == a >> b[4:0]);
+  pSRA:  assert final (op == {7'b0100000, 3'b101} -> out == $signed(a) >>> b[4:0]);
+  pOR:   assert final (op == {7'b0000000, 3'b110} -> out == (a | b));
+  pAND:  assert final (op == {7'b0000000, 3'b111} -> out == (a & b));
+
+endmodule