74 lines
2.7 KiB
Python
74 lines
2.7 KiB
Python
from amaranth import *
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from amaranth.asserts import *
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from .. import pfv
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__all__ = ["GPRCheck"]
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class GPRCheck(Elaboratable):
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"""General Purpose Registers check.
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Checks that reads from GPRs are consistent with the last value that was written to them.
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Also checks that simultaneous writes to multiple GPRs by the same instruction (e.g. a load
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with update) do not target the same register.
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"""
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def __init__(self):
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self.pre = Signal()
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self.post = Signal()
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self.pfv = pfv.Interface()
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def elaborate(self, platform):
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m = Module()
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spec_order = AnyConst(self.pfv.order.width)
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spec_gpr_index = AnyConst(5)
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gpr_ra_read = Signal()
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gpr_ra_write = Signal()
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gpr_rb_read = Signal()
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gpr_rs_read = Signal()
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gpr_rt_read = Signal()
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gpr_rt_write = Signal()
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gpr_conflict = Signal()
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gpr_written = Signal()
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gpr_shadow = Signal(64)
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m.d.comb += [
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gpr_ra_read .eq(self.pfv.ra.r_stb & (self.pfv.ra.index == spec_gpr_index)),
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gpr_ra_write.eq(self.pfv.ra.w_stb & (self.pfv.ra.index == spec_gpr_index)),
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gpr_rb_read .eq(self.pfv.rb.r_stb & (self.pfv.rb.index == spec_gpr_index)),
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gpr_rs_read .eq(self.pfv.rs.r_stb & (self.pfv.rs.index == spec_gpr_index)),
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gpr_rt_read .eq(self.pfv.rt.r_stb & (self.pfv.rt.index == spec_gpr_index)),
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gpr_rt_write.eq(self.pfv.rt.w_stb & (self.pfv.rt.index == spec_gpr_index)),
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]
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with m.If(self.pfv.stb & (self.pfv.order <= spec_order)):
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with m.If(gpr_ra_write & gpr_rt_write):
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m.d.sync += gpr_conflict.eq(1)
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with m.If(gpr_ra_write | gpr_rt_write):
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m.d.sync += gpr_written.eq(1)
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with m.If(gpr_ra_write):
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m.d.sync += gpr_shadow.eq(self.pfv.ra.w_data)
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with m.Else():
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m.d.sync += gpr_shadow.eq(self.pfv.rt.w_data)
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with m.If(self.post):
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m.d.sync += [
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Assume(Past(self.pfv.stb)),
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Assume(Past(self.pfv.order) == spec_order),
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Assert(gpr_written.implies(~gpr_conflict)),
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]
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with m.If(Past(gpr_ra_read)):
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m.d.sync += Assert(Past(gpr_shadow) == Past(self.pfv.ra.r_data))
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with m.If(Past(gpr_rb_read)):
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m.d.sync += Assert(Past(gpr_shadow) == Past(self.pfv.rb.r_data))
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with m.If(Past(gpr_rs_read)):
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m.d.sync += Assert(Past(gpr_shadow) == Past(self.pfv.rs.r_data))
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with m.If(Past(gpr_rt_read)):
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m.d.sync += Assert(Past(gpr_shadow) == Past(self.pfv.rt.r_data))
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return m
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