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