add(Pipeline_Reset.sv, pipeline_reset.cpp): Added Pipeline Reset Modu…

…le and Tests (#117)

* add(Pipeline_Reset.sv): Pipeline Reset Implement

* fix(branch_manager.cpp): FIxed random number gen

* add(pipeline_reset.cpp): Added Pipeline Reset Test

dv/CMakeLists.txt

@@ -3,11 +3,11 @@ find_package(nyu-util REQUIRED CONFIG)
 
 add_executable(tests)
 target_sources(tests PRIVATE
-  alu.cpp branch_eval.cpp pc.cpp ifid.cpp memwb.cpp gpr.cpp exmem.cpp branch_addr_calc.cpp idex.cpp branch_predictor.cpp
+  alu.cpp branch_eval.cpp pc.cpp ifid.cpp memwb.cpp gpr.cpp exmem.cpp branch_addr_calc.cpp idex.cpp branch_predictor.cpp pipeline_reset.cpp
 )
 nyu_link_sv(tests PRIVATE core)
 nyu_target_verilate(tests
-  TOP_MODULES Alu Branch_Eval PC IFID MEMWB GPR EXMEM Branch_Addr_Calc IDEX Branch_Predictor
+  TOP_MODULES Alu Branch_Eval PC IFID MEMWB GPR EXMEM Branch_Addr_Calc IDEX Branch_Predictor Pipeline_Reset
   ARGS COVERAGE
 )
 target_link_libraries(tests PRIVATE Catch2::Catch2WithMain nyu::covrecorder)

dv/branch_manager.cpp

@@ -31,8 +31,8 @@ TEST_CASE("Flush") {
     for (int i = 0; i < 1000; i++) {
         pred_taken = rand() % (int) (pow(2, 1) - 1);
         act_taken = rand() % (int) (pow(2, 1) - 1);
-        pred_pc = rand() % (int) (pow(32, 1) - 1);
-        pred_addr = rand() % (int) (pow(32, 1) - 1);
+        pred_pc = rand() % (int) (pow(2, 32) - 1);
+        pred_addr = rand() % (int) (pow(2, 32) - 1);
 
         model.clk = 0;
         model.eval();
@@ -78,8 +78,8 @@ TEST_CASE("Incorrect Prediction") {
     for (int i = 0; i < 1000; i++) {
         pred_taken = rand() % (int) (pow(2, 1) - 1);
         act_taken = ~pred_taken;
-        pred_pc = rand() % (int) (pow(32, 1) - 1);
-        pred_addr = rand() % (int) (pow(32, 1) - 1);
+        pred_pc = rand() % (int) (pow(2, 32) - 1);
+        pred_addr = rand() % (int) (pow(2, 32) - 1);
 
         model.clk = 0;
         model.eval();
@@ -128,8 +128,8 @@ TEST_CASE("Correct Prediction") {
     for (int i = 0; i < 1000; i++) {
         pred_taken = rand() % (int) (pow(2, 1) - 1);
         act_taken = pred_taken;
-        pred_pc = rand() % (int) (pow(32, 1) - 1);
-        pred_addr = rand() % (int) (pow(32, 1) - 1);
+        pred_pc = rand() % (int) (pow(2, 32) - 1);
+        pred_addr = rand() % (int) (pow(2, 32) - 1);
 
         model.clk = 0;
         model.eval();

dv/pipeline_reset.cpp

@@ -0,0 +1,55 @@
+#include <catch2/catch_test_macros.hpp>
+#include <VPipeline_Reset.h>
+#include <cstdint>
+#include <stdlib.h>  
+#include <math.h>
+
+/*
+Note: 
+The tests do not currently distinguish between High Z and 0 due to limitations of Verilator. 
+The module could be modified to provide a test output that is 0 when rstn is 0 and 1 when rstn is High Z, 
+but given the simplicity of this module that doesn't seem warrented at this point.
+ */
+
+
+TEST_CASE("flush == 0") { 
+    VPipeline_Reset model;
+
+    uint32_t npc_in;
+    uint32_t npc_corr;
+
+    for (int i = 0; i < 1000; i++) {
+        npc_in = rand() % (int) (pow(2, 32) - 1);
+        npc_corr = rand() % (int) (pow(2, 32) - 1);
+
+        model.flush = 0;
+        model.npc_in = npc_in;
+        model.npc_corr = npc_corr;
+        model.eval();
+
+        REQUIRE((uint32_t) model.npc == (uint32_t) npc_in);
+        REQUIRE(model.rstn == 0); //Verilator translates High Z outputs to 0 
+
+    }
+}
+
+TEST_CASE("flush == 1") { 
+    VPipeline_Reset model;
+
+    uint32_t npc_in;
+    uint32_t npc_corr;
+
+    for (int i = 0; i < 1000; i++) {
+        npc_in = rand() % (int) (pow(2, 32) - 1);
+        npc_corr = rand() % (int) (pow(2, 32) - 1);
+
+        model.flush = 1;
+        model.npc_in = npc_in;
+        model.npc_corr = npc_corr;
+        model.eval();
+
+        REQUIRE((uint32_t) model.npc == (uint32_t) npc_corr);
+        REQUIRE(model.rstn == 0); //Expect actual 0 output here, not High Z
+
+    }
+}

rtl/CMakeLists.txt

@@ -1,3 +1,3 @@
 nyu_add_sv(core
-  Alu.sv Branch_Eval.sv PC.sv IFID.sv MEMWB.sv GPR.sv EXMEM.sv Branch_Addr_Calc.sv IDEX.sv Branch_Predictor.sv
+  Alu.sv Branch_Eval.sv PC.sv IFID.sv MEMWB.sv GPR.sv EXMEM.sv Branch_Addr_Calc.sv IDEX.sv Branch_Predictor.sv Pipeline_Reset.sv
 )

rtl/Pipeline_Reset.sv

@@ -0,0 +1,22 @@
+module Pipeline_Reset #(
+  WordSize = 32
+)(
+  input [WordSize - 1:0] npc_in, npc_corr,
+  input flush,
+  output logic [WordSize - 1:0] npc,
+  output logic rstn
+);
+
+always_comb begin
+case(flush)
+0: begin
+    npc = npc_in;
+    rstn = 1'bZ;
+end
+1: begin
+    npc = npc_corr;
+    rstn = 0;
+end
+endcase
+end
+endmodule