From f0ad502e4651243d6a96194b3393bd460c0f7fc9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Karel=20Ko=C4=8D=C3=AD?= <cynerd@email.cz>
Date: Sun, 19 Nov 2017 21:23:04 +0100
Subject: Another huge pile of work for about two months

Well I should commit every change instead of this madness. I am not
documenting changes as all this is just improvements and implementation
progression.
---
 qtmips_machine/alu.cpp | 51 ++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 49 insertions(+), 2 deletions(-)

(limited to 'qtmips_machine/alu.cpp')

diff --git a/qtmips_machine/alu.cpp b/qtmips_machine/alu.cpp
index 5c74a5d..85bc804 100644
--- a/qtmips_machine/alu.cpp
+++ b/qtmips_machine/alu.cpp
@@ -1,6 +1,53 @@
 #include "alu.h"
+#include "qtmipsexception.h"
 
-Alu::Alu()
-{
+std::uint32_t alu_operate(enum AluOp operation, std::uint32_t s, std::uint32_t t, std::uint8_t sa) {
+    switch(operation) {
+        case ALU_OP_SLL:
+            return t << sa;
+        case ALU_OP_SRL:
+            return t >> sa;
+        case ALU_OP_SRA:
+            // TODO is this correct implementation? (Shouldn't we be masking top most bit?)
+            return (t >> sa) | (t & 0x80000000);
+        case ALU_OP_SLLV:
+            return t << s;
+        case ALU_OP_SRLV:
+            return t >> s;
+        case ALU_OP_SRAV:
+            // TODO is this correct implementation? (Shouldn't we be masking top most bit?)
+            return (t >> s) | (t & 0x80000000);
+        case ALU_OP_ADD:
+            if (s > (0xFFFFFFFF - t))
+                throw QTMIPS_EXCEPTION(Overflow, "ADD operation overflow/underflow", QString::number(s) + QString(" + ") + QString::number(t));
+            // Intentional falltrough
+        case ALU_OP_ADDU:
+            return s + t;
+        case ALU_OP_SUB:
+            if (s < t)
+                throw QTMIPS_EXCEPTION(Overflow, "SUB operation overflow/underflow", QString::number(s) + QString(" - ") + QString::number(t));
+            // Intentional falltrough
+        case ALU_OP_SUBU:
+            return s - t;
+        case ALU_OP_AND:
+            return s & t;
+        case ALU_OP_OR:
+            return s | t;
+        case ALU_OP_XOR:
+            return s ^ t;
+        case ALU_OP_NOR:
+            return ~(s | t);
+        case ALU_OP_SLTU:
+            // TODO is this correct implementation? (this is two's complement signed representation so do we care?)
+            // Intentional falltrough
+        case ALU_OP_SLT:
+            return (s < t) ? 1 : 0;
+        default:
+            throw QTMIPS_EXCEPTION(UnsupportedAluOperation, "Unknown ALU operation", QString::number(operation, 16));
+    }
+}
 
+QString alu_str(enum AluOp operation, std::uint32_t s, std::uint32_t t, std::uint8_t sa) {
+    // TODO
+    return QString("");
 }
-- 
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