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58 #ifndef __ARCH_X86_PREDECODER_HH__
59 #define __ARCH_X86_PREDECODER_HH__
61 #include "arch/x86/types.hh"
62 #include "base/bitfield.hh"
63 #include "sim/host.hh"
72 //These are defined and documented in predecoder_tables.cc
73 static const uint8_t Prefixes[256];
74 static const uint8_t UsesModRM[2][256];
75 static const uint8_t ImmediateType[2][256];
76 static const uint8_t SizeTypeToSize[3][10];
80 //The bytes to be predecoded
82 //The pc of the start of fetchChunk
84 //The offset into fetchChunk of current processing
86 //The extended machine instruction being generated
89 inline uint8_t getNextByte()
91 return (fetchChunk >> (offset * 8)) & 0xff;
94 void getImmediate(int &collected, uint64_t ¤t, int size)
96 //Figure out how many bytes we still need to get for the
98 int toGet = size - collected;
99 //Figure out how many bytes are left in our "buffer"
100 int remaining = sizeof(MachInst) - offset;
101 //Get as much as we need, up to the amount available.
102 toGet = toGet > remaining ? remaining : toGet;
104 //Shift the bytes we want to be all the way to the right
105 uint64_t partialDisp = fetchChunk >> (offset * 8);
106 //Mask off what we don't want
107 partialDisp &= mask(toGet * 8);
108 //Shift it over to overlay with our displacement.
109 partialDisp <<= (displacementCollected * 8);
110 //Put it into our displacement
111 current |= partialDisp;
112 //Update how many bytes we've collected.
117 inline void consumeByte()
120 assert(offset <= sizeof(MachInst));
121 if(offset == sizeof(MachInst))
125 inline void consumeBytes(int numBytes)
128 assert(offset <= sizeof(MachInst));
129 if(offset == sizeof(MachInst))
133 //State machine state
135 //Whether or not we're out of bytes
137 //Whether we've completed generating an ExtMachInst
139 //The size of the displacement value
140 int displacementSize;
141 int displacementCollected;
142 //The size of the immediate value
144 int immediateCollected;
153 //We should never get to this state. Getting here is an error.
159 //Functions to handle each of the states
160 State doPrefixState(uint8_t);
161 State doOpcodeState(uint8_t);
162 State doModRMState(uint8_t);
163 State doSIBState(uint8_t);
164 State doDisplacementState();
165 State doImmediateState();
168 Predecoder(ThreadContext * _tc) :
169 tc(_tc), basePC(0), offset(0),
170 outOfBytes(true), emiIsReady(false),
174 ThreadContext * getTC()
179 void setTC(ThreadContext * _tc)
186 //Use this to give data to the predecoder. This should be used
187 //when there is control flow.
188 void moreBytes(Addr currPC, Addr off, MachInst data)
193 assert(off < sizeof(MachInst));
198 //Use this to give data to the predecoder. This should be used
199 //when instructions are executed in order.
200 void moreBytes(MachInst machInst)
202 moreBytes(basePC + sizeof(machInst), 0, machInst);
210 bool extMachInstReady()
215 //This returns a constant reference to the ExtMachInst to avoid a copy
216 const ExtMachInst & getExtMachInst()
225 #endif // __ARCH_X86_PREDECODER_HH__