From 5f28f80c4e25a56cd444914c2f0b3da5e7fdb088 Mon Sep 17 00:00:00 2001
From: Lizzy Hunt <elizabeth.hunt@simponic.xyz>
Date: Mon, 10 Apr 2023 09:17:11 -0600
Subject: Initial commit - building

---
 submit/RegisterAllocator.java | 126 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 submit/RegisterAllocator.java

(limited to 'submit/RegisterAllocator.java')

diff --git a/submit/RegisterAllocator.java b/submit/RegisterAllocator.java
new file mode 100644
index 0000000..ce18b2b
--- /dev/null
+++ b/submit/RegisterAllocator.java
@@ -0,0 +1,126 @@
+/*
+ */
+package submit;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+/**
+ *
+ *
+ *
+ */
+public final class RegisterAllocator {
+
+    // True if t is used
+    private final boolean[] t = new boolean[10];
+    private final boolean[] s = new boolean[8];
+    private final Set<String> used = new HashSet<>();
+
+    public RegisterAllocator() {
+        clearAll();
+    }
+
+    public String getT() {
+        for (int i = 0; i < t.length; ++i) {
+            if (!t[i]) {
+                t[i] = true;
+                String str = "$t" + i;
+                used.add(str);
+                return str;
+            }
+        }
+        return null;
+    }
+
+//    public String getS() {
+//        for (int i = 0; i < s.length; ++i) {
+//            if (!s[i]) {
+//                s[i] = true;
+//                String str = "$s" + i;
+//                used.add(str);
+//                return str;
+//            }
+//        }
+//        return null;
+//    }
+
+    // Returns the number of bytes used to save the registers
+    public int saveRestore(StringBuilder code, int baseOffset, boolean s_or_t, boolean save) {
+        boolean[] r = s;
+        String prefix = "$s";
+        if (!s_or_t) {
+            r = t;
+            prefix = "$t";
+        }
+        String instruction = "sw";
+        if (!save) {
+            instruction = "lw";
+        }
+        int offset = 0;
+        for (int i = 0; i < r.length; ++i) {
+            if (r[i]) {
+                offset -= 4;
+                String str = prefix + i;
+                code.append(instruction).append(" ").append(str).append(" ").append(offset-baseOffset).append("($sp)\n");
+            }
+        }
+        return -offset;
+    }
+
+//    public int saveS(StringBuilder code, int baseOffset) {
+//        return saveRestore(code, baseOffset, true, true);
+//    }
+
+    public int saveT(StringBuilder code, int baseOffset) {
+        return saveRestore(code, baseOffset, false, true);
+    }
+
+//    public int restoreS(StringBuilder code, int baseOffset) {
+//        return saveRestore(code, baseOffset, true, false);
+//    }
+
+    public int restoreT(StringBuilder code, int baseOffset) {
+        return saveRestore(code, baseOffset, false, false);
+    }
+
+    public List<String> getUsed() {
+        return new ArrayList<>(used);
+    }
+
+    /**
+     * Any time you call this method you should seriously consider adding a
+     * corresponding clear() call.
+     *
+     * @return
+     */
+    public String getAny() {
+//        String availS = getS();
+//        if (availS != null) {
+//            return availS;
+//        }
+        String t = getT();
+        if (t == null) {
+            throw new RuntimeException("Out of registers");
+        }
+        return t;
+    }
+
+    public void clear(String reg) {
+        if (reg.charAt(1) == 's') {
+            s[Integer.parseInt(reg.substring(2))] = false;
+        } else if (reg.charAt(1) == 't') {
+            t[Integer.parseInt(reg.substring(2))] = false;
+        } else {
+            throw new RuntimeException("Unexpected register in clear");
+        }
+    }
+
+    public void clearAll() {
+        Arrays.fill(t, false);
+        Arrays.fill(s, false);
+    }
+}
-- 
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