1 files changed, 151 insertions, 0 deletions
diff --git a/Homework/cs5300/compiler/p5-compiler/submit/RegisterAllocator.java b/Homework/cs5300/compiler/p5-compiler/submit/RegisterAllocator.java
new file mode 100644
index 0000000..b0c9d03
--- /dev/null
+++ b/Homework/cs5300/compiler/p5-compiler/submit/RegisterAllocator.java
@@ -0,0 +1,151 @@
+/*
+ */
+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 getRegisterOrLoadIntoRegister(MIPSResult result,
+                                              StringBuilder code) {
+    if (result.getRegister() != null) {
+      return result.getRegister();
+    }
+    String reg = result.getAddress();
+    return this.loadIntoRegister(result, code, reg);
+  }
+
+  public String loadIntoRegister(MIPSResult result, StringBuilder code,
+                                 String register) {
+    return loadIntoRegisterWithOffset(result, code, register, 0);
+  }
+
+  public String loadIntoRegisterWithOffset(MIPSResult result,
+                                           StringBuilder code, String register,
+                                           int offset) {
+    code.append(
+        String.format("lw %s %d(%s)\n", register, offset, result.getAddress()));
+
+    return register;
+  }
+
+  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);
+  }
+}