137 lines
3.6 KiB
Python
137 lines
3.6 KiB
Python
"""
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RISC-V Encoding recipes.
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The encoding recipes defined here more or less correspond to the RISC-V native
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instruction formats described in the reference:
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The RISC-V Instruction Set Manual
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Volume I: User-Level ISA
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Version 2.1
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"""
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from __future__ import absolute_import
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from cdsl.isa import EncRecipe
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from cdsl.predicates import IsSignedInt
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from base.formats import Binary, BinaryImm, MultiAry, IntCompare, IntCompareImm
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from base.formats import UnaryImm, BranchIcmp, Branch, Jump, Call
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from .registers import GPR
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# The low 7 bits of a RISC-V instruction is the base opcode. All 32-bit
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# instructions have 11 as the two low bits, with bits 6:2 determining the base
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# opcode.
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#
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# Encbits for the 32-bit recipes are opcode[6:2] | (funct3 << 5) | ...
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# The functions below encode the encbits.
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def LOAD(funct3):
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# type: (int) -> int
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assert funct3 <= 0b111
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return 0b00000 | (funct3 << 5)
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def STORE(funct3):
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# type: (int) -> int
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assert funct3 <= 0b111
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return 0b01000 | (funct3 << 5)
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def BRANCH(funct3):
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# type: (int) -> int
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assert funct3 <= 0b111
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return 0b11000 | (funct3 << 5)
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def JALR(funct3=0):
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# type: (int) -> int
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assert funct3 <= 0b111
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return 0b11001 | (funct3 << 5)
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def JAL():
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# type: () -> int
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return 0b11011
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def OPIMM(funct3, funct7=0):
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# type: (int, int) -> int
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assert funct3 <= 0b111
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return 0b00100 | (funct3 << 5) | (funct7 << 8)
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def OPIMM32(funct3, funct7=0):
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# type: (int, int) -> int
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assert funct3 <= 0b111
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return 0b00110 | (funct3 << 5) | (funct7 << 8)
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def OP(funct3, funct7):
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# type: (int, int) -> int
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assert funct3 <= 0b111
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assert funct7 <= 0b1111111
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return 0b01100 | (funct3 << 5) | (funct7 << 8)
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def OP32(funct3, funct7):
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# type: (int, int) -> int
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assert funct3 <= 0b111
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assert funct7 <= 0b1111111
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return 0b01110 | (funct3 << 5) | (funct7 << 8)
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def AIUPC():
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# type: () -> int
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return 0b00101
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def LUI():
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# type: () -> int
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return 0b01101
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# R-type 32-bit instructions: These are mostly binary arithmetic instructions.
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# The encbits are `opcode[6:2] | (funct3 << 5) | (funct7 << 8)
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R = EncRecipe('R', Binary, size=4, ins=(GPR, GPR), outs=GPR)
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# R-type with an immediate shift amount instead of rs2.
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Rshamt = EncRecipe('Rshamt', BinaryImm, size=4, ins=GPR, outs=GPR)
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# R-type encoding of an integer comparison.
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Ricmp = EncRecipe('Ricmp', IntCompare, size=4, ins=(GPR, GPR), outs=GPR)
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I = EncRecipe(
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'I', BinaryImm, size=4, ins=GPR, outs=GPR,
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instp=IsSignedInt(BinaryImm.imm, 12))
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# I-type encoding of an integer comparison.
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Iicmp = EncRecipe(
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'Iicmp', IntCompareImm, size=4, ins=GPR, outs=GPR,
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instp=IsSignedInt(IntCompareImm.imm, 12))
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# I-type encoding for `jalr` as a return instruction. We won't use the
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# immediate offset.
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# The variable return values are not encoded.
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Iret = EncRecipe('Iret', MultiAry, size=4, ins=GPR, outs=())
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# U-type instructions have a 20-bit immediate that targets bits 12-31.
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U = EncRecipe(
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'U', UnaryImm, size=4, ins=(), outs=GPR,
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instp=IsSignedInt(UnaryImm.imm, 32, 12))
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# UJ-type unconditional branch instructions.
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UJ = EncRecipe('UJ', Jump, size=4, ins=(), outs=(), branch_range=(0, 21))
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UJcall = EncRecipe('UJcall', Call, size=4, ins=(), outs=())
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# SB-type branch instructions.
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# TODO: These instructions have a +/- 4 KB branch range. How to encode that
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# constraint?
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SB = EncRecipe(
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'SB', BranchIcmp, size=4,
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ins=(GPR, GPR), outs=(),
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branch_range=(0, 13))
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# SB-type branch instruction with rs2 fixed to zero.
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SBzero = EncRecipe(
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'SBzero', Branch, size=4,
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ins=(GPR), outs=(),
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branch_range=(0, 13))
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