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37 * Authors: Andrew Bardsley
43 * Decode collects macro-ops from Fetch2 and splits them into micro-ops
47 #ifndef __CPU_MINOR_DECODE_HH__
48 #define __CPU_MINOR_DECODE_HH__
50 #include "cpu/minor/buffers.hh"
51 #include "cpu/minor/cpu.hh"
52 #include "cpu/minor/dyn_inst.hh"
53 #include "cpu/minor/pipe_data.hh"
58 /* Decode takes instructions from Fetch2 and decomposes them into micro-ops
59 * to feed to Execute. It generates a new sequence number for each
60 * instruction: execSeqNum.
62 class Decode : public Named
65 /** Pointer back to the containing CPU */
68 /** Input port carrying macro instructions from Fetch2 */
69 Latch<ForwardInstData>::Output inp;
70 /** Output port carrying micro-op decomposed instructions to Execute */
71 Latch<ForwardInstData>::Input out;
73 /** Interface to reserve space in the next stage */
74 Reservable &nextStageReserve;
76 /** Width of output of this stage/input of next in instructions */
77 unsigned int outputWidth;
79 /** If true, more than one input word can be processed each cycle if
80 * there is room in the output to contain its processed data */
81 bool processMoreThanOneInput;
84 /* Public for Pipeline to be able to pass it to Fetch2 */
85 InputBuffer<ForwardInstData> inputBuffer;
88 /** Data members after this line are cycle-to-cycle state */
90 /** Index into the inputBuffer's head marking the start of unhandled
92 unsigned int inputIndex;
94 /** True when we're in the process of decomposing a micro-op and
95 * microopPC will be valid. This is only the case when there isn't
96 * sufficient space in Executes input buffer to take the whole of a
97 * decomposed instruction and some of that instructions micro-ops must
98 * be generated in a later cycle */
100 TheISA::PCState microopPC;
102 /** Source of execSeqNums to number instructions. */
103 InstSeqNum execSeqNum;
105 /** Blocked indication for report */
109 /** Get a piece of data to work on, or 0 if there is no data. */
110 const ForwardInstData *getInput();
112 /** Pop an element off the input buffer, if there are any */
116 Decode(const std::string &name,
118 MinorCPUParams ¶ms,
119 Latch<ForwardInstData>::Output inp_,
120 Latch<ForwardInstData>::Input out_,
121 Reservable &next_stage_input_buffer);
124 /** Pass on input/buffer data to the output if you can */
127 void minorTrace() const;
129 /** Is this stage drained? For Decoed, draining is initiated by
130 * Execute halting Fetch1 causing Fetch2 to naturally drain
131 * into Decode and on to Execute which is responsible for
132 * actually killing instructions */
138 #endif /* __CPU_MINOR_DECODE_HH__ */