From 55e1bc746a45118e14554c957b4ee4663039d9af Mon Sep 17 00:00:00 2001
From: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Date: Sun, 3 Feb 2019 11:52:53 +0100
Subject: Implement BREAK instruction to stop continuous execution.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
---
 qtmips_machine/alu.cpp           | 2 ++
 qtmips_machine/alu.h             | 1 +
 qtmips_machine/core.cpp          | 5 +++++
 qtmips_machine/core.h            | 1 +
 qtmips_machine/instruction.cpp   | 7 ++++++-
 qtmips_machine/instruction.h     | 1 +
 qtmips_machine/qtmipsmachine.cpp | 9 ++++++---
 7 files changed, 22 insertions(+), 4 deletions(-)

(limited to 'qtmips_machine')

diff --git a/qtmips_machine/alu.cpp b/qtmips_machine/alu.cpp
index bb3a745..49c41a3 100644
--- a/qtmips_machine/alu.cpp
+++ b/qtmips_machine/alu.cpp
@@ -35,6 +35,8 @@ std::uint32_t machine::alu_operate(enum AluOp operation, std::uint32_t s, std::u
         case ALU_OP_MOVN:
             // Same note as for MOVZ applies here
             return t != 0 ? s : 0;
+        case ALU_OP_BREAK:
+             return 0;
         case ALU_OP_MFHI:
             return regs->read_hi_lo(true);
         case ALU_OP_MTHI:
diff --git a/qtmips_machine/alu.h b/qtmips_machine/alu.h
index 7846244..351e124 100644
--- a/qtmips_machine/alu.h
+++ b/qtmips_machine/alu.h
@@ -19,6 +19,7 @@ enum AluOp : std::uint8_t {
     ALU_OP_JALR,
     ALU_OP_MOVZ,
     ALU_OP_MOVN,
+    ALU_OP_BREAK = 13,
     ALU_OP_MFHI = 16,
     ALU_OP_MTHI,
     ALU_OP_MFLO,
diff --git a/qtmips_machine/core.cpp b/qtmips_machine/core.cpp
index 7793305..3d5541f 100644
--- a/qtmips_machine/core.cpp
+++ b/qtmips_machine/core.cpp
@@ -146,6 +146,8 @@ struct Core::dtDecode Core::decode(const struct dtFetch &dt) {
     bool bjr_req_rs = dec.flags & DM_BJR_REQ_RS;
     if (dt.inst.opcode() == 0) {
         switch (dt.inst.funct()) {
+            case ALU_OP_BREAK:
+                FALLTROUGH
             case ALU_OP_MTHI:
                 FALLTROUGH
             case ALU_OP_MTLO:
@@ -279,6 +281,9 @@ struct Core::dtMemory Core::memory(const struct dtExecute &dt) {
     emit memory_memwrite_value(dt.memwrite);
     emit memory_regw_num_value(dt.rwrite);
 
+    if (dt.inst.is_break())
+        emit memory_break_reached();
+
     return {
         .inst = dt.inst,
         .regwrite = dt.regwrite,
diff --git a/qtmips_machine/core.h b/qtmips_machine/core.h
index 00dbee6..d97f4c1 100644
--- a/qtmips_machine/core.h
+++ b/qtmips_machine/core.h
@@ -73,6 +73,7 @@ signals:
     void memory_memwrite_value(std::uint32_t);
     void memory_memread_value(std::uint32_t);
     void memory_regw_num_value(std::uint32_t);
+    void memory_break_reached();
     void writeback_value(std::uint32_t);
     void writeback_regw_value(std::uint32_t);
     void writeback_regw_num_value(std::uint32_t);
diff --git a/qtmips_machine/instruction.cpp b/qtmips_machine/instruction.cpp
index 7feebd3..0ca7b24 100644
--- a/qtmips_machine/instruction.cpp
+++ b/qtmips_machine/instruction.cpp
@@ -1,4 +1,5 @@
 #include "instruction.h"
+#include "alu.h"
 #include "qtmipsexception.h"
 
 using namespace machine;
@@ -108,7 +109,7 @@ static const struct AluInstructionMap alu_instruction_map[] = {
     {"MOVZ"},
     {"MOVN"},
     AIM_UNKNOWN,
-    AIM_UNKNOWN,
+    {"BREAK"},
     AIM_UNKNOWN,
     AIM_UNKNOWN,
     {"MFHI"},
@@ -231,6 +232,10 @@ bool Instruction::is_store() const {
     return im.is_store;
 }
 
+bool Instruction::is_break() const {
+    return opcode() == 0 && funct() == ALU_OP_BREAK;
+}
+
 bool Instruction::operator==(const Instruction &c) const {
     return (this->data() == c.data());
 }
diff --git a/qtmips_machine/instruction.h b/qtmips_machine/instruction.h
index 1e44a1a..a93be65 100644
--- a/qtmips_machine/instruction.h
+++ b/qtmips_machine/instruction.h
@@ -33,6 +33,7 @@ public:
     std::uint32_t data() const;
     enum Type type() const;
     bool is_store() const; // Store instructions requires some additional handling so identify them
+    bool is_break() const;
 
     bool operator==(const Instruction &c) const;
     bool operator!=(const Instruction &c) const;
diff --git a/qtmips_machine/qtmipsmachine.cpp b/qtmips_machine/qtmipsmachine.cpp
index da4516a..75d8b8e 100644
--- a/qtmips_machine/qtmipsmachine.cpp
+++ b/qtmips_machine/qtmipsmachine.cpp
@@ -81,7 +81,8 @@ void QtMipsMachine::play() {
 }
 
 void QtMipsMachine::pause() {
-    CTL_GUARD;
+    if (stat != ST_BUSY)
+        CTL_GUARD;
     set_status(ST_READY);
     run_t->stop();
 }
@@ -103,8 +104,10 @@ void QtMipsMachine::step() {
         run_t->stop();
         set_status(ST_EXIT);
         emit program_exit();
-    } else
-        set_status(stat_prev);
+    } else {
+        if (stat == ST_BUSY)
+            set_status(stat_prev);
+    }
 }
 
 void QtMipsMachine::restart() {
-- 
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