50 lines
1.9 KiB
Java
Executable File
50 lines
1.9 KiB
Java
Executable File
package midend.llvm.instr;
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import backend.mips.MipsBuilder;
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import midend.llvm.type.IrArrayType;
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import midend.llvm.type.IrPointerType;
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import midend.llvm.type.IrType;
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import backend.mips.Register;
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import backend.mips.instr.MipsAlu;
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import backend.mips.instr.MipsLs;
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import backend.mips.instr.type.MipsAluType;
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import backend.mips.instr.type.MipsLsType;
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public class AllocateInstr extends IrInstr {
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private IrType pointeeType;
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public AllocateInstr(IrType pointeeType, String name) { // name即为局部变量的name，因为要声明一个局部变量
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super(new IrPointerType(pointeeType), name, IrInstrType.ALLOCA);
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this.pointeeType = pointeeType;
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}
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public IrType getPointeeType() {
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return pointeeType;
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}
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public String toString() {
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return getName() + " = alloca " + this.pointeeType;
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}
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public void toMips() {
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// 想法：在栈上分配数据所需要的空间，再分配四字节的指针，这就是个指针，将其当作指针就好理解了
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if (pointeeType instanceof IrArrayType) {
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MipsBuilder.allocaOffset(4 * ((IrArrayType) pointeeType).getSize());
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} else {
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MipsBuilder.allocaOffset(4);
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}
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Register reg = MipsBuilder.getRegister(this);
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if (reg == null) { // 未分配寄存器情况
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int offset = MipsBuilder.getOffset();
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new MipsAlu(MipsAluType.ADDI, Register.K0, Register.SP, offset);
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MipsBuilder.allocaOffset(this); // 将该变量的偏移量设置为其指针的偏移量，后续取值先取指针，再根据指针取值
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offset = MipsBuilder.getOffset();
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new MipsLs(MipsLsType.SW, Register.K0, Register.SP, offset);
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} else {
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int offset = MipsBuilder.getOffset();
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new MipsAlu(MipsAluType.ADDI, reg, Register.SP, offset);
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}
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}
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}
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