2fe61e83f6
- cdsl.predicates defines classes for describing predicates. - cdsl.settings defines classes for describing settings. - base.settings defines shared settings.
76 lines
1.9 KiB
Python
76 lines
1.9 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 cretonne import EncRecipe
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from cretonne.formats import Binary, BinaryImm
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from cdsl.predicates import IsSignedInt
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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 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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# 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)
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# R-type with an immediate shift amount instead of rs2.
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Rshamt = EncRecipe('Rshamt', BinaryImm)
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I = EncRecipe('I', BinaryImm, instp=IsSignedInt(BinaryImm.imm, 12))
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