832247019b
RISC architectures that take a return address in a register can use a special-purpose `link` return value to do so.
117 lines
4.2 KiB
Python
117 lines
4.2 KiB
Python
"""
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RISC-V Encodings.
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"""
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from __future__ import absolute_import
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from base import instructions as base
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from base.immediates import intcc
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from .defs import RV32, RV64
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from .recipes import OPIMM, OPIMM32, OP, OP32, LUI, BRANCH, JALR, JAL
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from .recipes import R, Rshamt, Ricmp, I, Iicmp, Iret
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from .recipes import U, UJ, UJcall, SB, SBzero
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from .settings import use_m
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from cdsl.ast import Var
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# Dummies for instruction predicates.
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x = Var('x')
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y = Var('y')
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dest = Var('dest')
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args = Var('args')
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# Basic arithmetic binary instructions are encoded in an R-type instruction.
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for inst, inst_imm, f3, f7 in [
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(base.iadd, base.iadd_imm, 0b000, 0b0000000),
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(base.isub, None, 0b000, 0b0100000),
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(base.bxor, base.bxor_imm, 0b100, 0b0000000),
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(base.bor, base.bor_imm, 0b110, 0b0000000),
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(base.band, base.band_imm, 0b111, 0b0000000)
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]:
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RV32.enc(inst.i32, R, OP(f3, f7))
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RV64.enc(inst.i64, R, OP(f3, f7))
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# Immediate versions for add/xor/or/and.
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if inst_imm:
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RV32.enc(inst_imm.i32, I, OPIMM(f3))
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RV64.enc(inst_imm.i64, I, OPIMM(f3))
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# 32-bit ops in RV64.
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RV64.enc(base.iadd.i32, R, OP32(0b000, 0b0000000))
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RV64.enc(base.isub.i32, R, OP32(0b000, 0b0100000))
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# There are no andiw/oriw/xoriw variations.
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RV64.enc(base.iadd_imm.i32, I, OPIMM32(0b000))
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# Dynamic shifts have the same masking semantics as the cton base instructions.
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for inst, inst_imm, f3, f7 in [
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(base.ishl, base.ishl_imm, 0b001, 0b0000000),
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(base.ushr, base.ushr_imm, 0b101, 0b0000000),
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(base.sshr, base.sshr_imm, 0b101, 0b0100000),
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]:
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RV32.enc(inst.i32.i32, R, OP(f3, f7))
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RV64.enc(inst.i64.i64, R, OP(f3, f7))
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RV64.enc(inst.i32.i32, R, OP32(f3, f7))
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# Allow i32 shift amounts in 64-bit shifts.
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RV64.enc(inst.i64.i32, R, OP(f3, f7))
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RV64.enc(inst.i32.i64, R, OP32(f3, f7))
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# Immediate shifts.
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RV32.enc(inst_imm.i32, Rshamt, OPIMM(f3, f7))
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RV64.enc(inst_imm.i64, Rshamt, OPIMM(f3, f7))
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RV64.enc(inst_imm.i32, Rshamt, OPIMM32(f3, f7))
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# Signed and unsigned integer 'less than'. There are no 'w' variants for
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# comparing 32-bit numbers in RV64.
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RV32.enc(base.icmp.i32(intcc.slt, x, y), Ricmp, OP(0b010, 0b0000000))
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RV64.enc(base.icmp.i64(intcc.slt, x, y), Ricmp, OP(0b010, 0b0000000))
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RV32.enc(base.icmp.i32(intcc.ult, x, y), Ricmp, OP(0b011, 0b0000000))
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RV64.enc(base.icmp.i64(intcc.ult, x, y), Ricmp, OP(0b011, 0b0000000))
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RV32.enc(base.icmp_imm.i32(intcc.slt, x, y), Iicmp, OPIMM(0b010))
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RV64.enc(base.icmp_imm.i64(intcc.slt, x, y), Iicmp, OPIMM(0b010))
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RV32.enc(base.icmp_imm.i32(intcc.ult, x, y), Iicmp, OPIMM(0b011))
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RV64.enc(base.icmp_imm.i64(intcc.ult, x, y), Iicmp, OPIMM(0b011))
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# Integer constants with the low 12 bits clear are materialized by lui.
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RV32.enc(base.iconst.i32, U, LUI())
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RV64.enc(base.iconst.i32, U, LUI())
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RV64.enc(base.iconst.i64, U, LUI())
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# "M" Standard Extension for Integer Multiplication and Division.
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# Gated by the `use_m` flag.
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RV32.enc(base.imul.i32, R, OP(0b000, 0b0000001), isap=use_m)
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RV64.enc(base.imul.i64, R, OP(0b000, 0b0000001), isap=use_m)
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RV64.enc(base.imul.i32, R, OP32(0b000, 0b0000001), isap=use_m)
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# Control flow.
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# Unconditional branches.
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RV32.enc(base.jump, UJ, JAL())
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RV64.enc(base.jump, UJ, JAL())
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RV32.enc(base.call, UJcall, JAL())
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RV64.enc(base.call, UJcall, JAL())
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# Conditional branches.
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for cond, f3 in [
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(intcc.eq, 0b000),
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(intcc.ne, 0b001),
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(intcc.slt, 0b100),
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(intcc.sge, 0b101),
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(intcc.ult, 0b110),
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(intcc.uge, 0b111)
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]:
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RV32.enc(base.br_icmp.i32(cond, x, y, dest, args), SB, BRANCH(f3))
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RV64.enc(base.br_icmp.i64(cond, x, y, dest, args), SB, BRANCH(f3))
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for inst, f3 in [
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(base.brz, 0b000),
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(base.brnz, 0b001)
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]:
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RV32.enc(inst.i32, SBzero, BRANCH(f3))
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RV64.enc(inst.i64, SBzero, BRANCH(f3))
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RV32.enc(inst.b1, SBzero, BRANCH(f3))
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RV64.enc(inst.b1, SBzero, BRANCH(f3))
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# Returns are a special case of JALR using %x1 to hold the return address.
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# The return address is provided by a special-purpose `link` return value that
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# is added by legalize_signature().
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RV32.enc(base.x_return, Iret, JALR())
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RV64.enc(base.x_return, Iret, JALR())
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