From 00cdddd4f3e2e6c93150809b94e83086c4a704c7 Mon Sep 17 00:00:00 2001
From: Catherine <whitequark@whitequark.org>
Date: Sat, 25 Nov 2023 00:38:33 +0000
Subject: [PATCH] hdl: remove deprecated `Sample`, `Past`, `Stable`, `Rose`,
 `Fell`.

---
 amaranth/asserts.py    |  6 ++-
 amaranth/back/rtlil.py | 16 +++++---
 amaranth/build/plat.py |  3 +-
 amaranth/hdl/ast.py    | 74 +----------------------------------
 amaranth/hdl/dsl.py    |  4 +-
 amaranth/hdl/ir.py     |  7 ++--
 amaranth/hdl/xfrm.py   | 88 ------------------------------------------
 amaranth/sim/_pyrtl.py |  3 --
 docs/changes.rst       |  1 +
 tests/test_hdl_ast.py  | 35 +----------------
 tests/test_hdl_dsl.py  | 19 ---------
 tests/test_hdl_xfrm.py | 48 -----------------------
 tests/test_sim.py      | 47 ----------------------
 13 files changed, 23 insertions(+), 328 deletions(-)

diff --git a/amaranth/asserts.py b/amaranth/asserts.py
index b0e97b9cb..6ff2037a4 100644
--- a/amaranth/asserts.py
+++ b/amaranth/asserts.py
@@ -1,2 +1,4 @@
-from .hdl.ast import AnyConst, AnySeq, Assert, Assume, Cover
-from .hdl.ast import Past, Stable, Rose, Fell, Initial
+from .hdl.ast import AnyConst, AnySeq, Initial, Assert, Assume, Cover
+
+
+__all__ = ["AnyConst", "AnySeq", "Initial", "Assert", "Assume", "Cover"]
diff --git a/amaranth/back/rtlil.py b/amaranth/back/rtlil.py
index bd6a3f8ac..3af2f0aec 100644
--- a/amaranth/back/rtlil.py
+++ b/amaranth/back/rtlil.py
@@ -398,12 +398,6 @@ def on_ClockSignal(self, value):
     def on_ResetSignal(self, value):
         raise NotImplementedError # :nocov:
 
-    def on_Sample(self, value):
-        raise NotImplementedError # :nocov:
-
-    def on_Initial(self, value):
-        raise NotImplementedError # :nocov:
-
     def on_Cat(self, value):
         return "{{ {} }}".format(" ".join(reversed([self(o) for o in value.parts])))
 
@@ -498,6 +492,13 @@ def on_AnySeq(self, value):
         self.s.anys[value] = res
         return res
 
+    def on_Initial(self, value):
+        res = self.s.rtlil.wire(width=1, src=_src(value.src_loc))
+        self.s.rtlil.cell("$initstate", ports={
+            "\\Y": res,
+        }, src=_src(value.src_loc))
+        return res
+
     def on_Signal(self, value):
         wire_curr, wire_next = self.s.resolve(value)
         return wire_curr
@@ -646,6 +647,9 @@ def on_AnyConst(self, value):
     def on_AnySeq(self, value):
         raise TypeError # :nocov:
 
+    def on_Initial(self, value):
+        raise TypeError # :nocov:
+
     def on_Operator(self, value):
         if value.operator in ("u", "s"):
             # These operators are transparent on the LHS.
diff --git a/amaranth/build/plat.py b/amaranth/build/plat.py
index 5a56b29f5..d13217876 100644
--- a/amaranth/build/plat.py
+++ b/amaranth/build/plat.py
@@ -9,7 +9,7 @@
 from .. import __version__
 from .._toolchain import *
 from ..hdl import *
-from ..hdl.xfrm import SampleLowerer, DomainLowerer
+from ..hdl.xfrm import DomainLowerer
 from ..lib.cdc import ResetSynchronizer
 from ..back import rtlil, verilog
 from .res import *
@@ -143,7 +143,6 @@ def prepare(self, elaboratable, name="top", **kwargs):
         self._prepared = True
 
         fragment = Fragment.get(elaboratable, self)
-        fragment = SampleLowerer()(fragment)
         fragment._propagate_domains(self.create_missing_domain, platform=self)
         fragment = DomainLowerer()(fragment)
 
diff --git a/amaranth/hdl/ast.py b/amaranth/hdl/ast.py
index af5746522..33e1ef949 100644
--- a/amaranth/hdl/ast.py
+++ b/amaranth/hdl/ast.py
@@ -20,7 +20,7 @@
     "Array", "ArrayProxy",
     "Signal", "ClockSignal", "ResetSignal",
     "ValueCastable", "ValueLike",
-    "Sample", "Past", "Stable", "Rose", "Fell", "Initial",
+    "Initial",
     "Statement", "Switch",
     "Property", "Assign", "Assert", "Assume", "Cover",
     "ValueKey", "ValueDict", "ValueSet", "SignalKey", "SignalDict", "SignalSet",
@@ -1549,70 +1549,6 @@ def __new__(cls, *args, **kwargs):
         raise TypeError("ValueLike is an abstract class and cannot be constructed")
 
 
-# TODO(amaranth-0.5): remove
-@final
-class Sample(Value):
-    """Value from the past.
-
-    A ``Sample`` of an expression is equal to the value of the expression ``clocks`` clock edges
-    of the ``domain`` clock back. If that moment is before the beginning of time, it is equal
-    to the value of the expression calculated as if each signal had its reset value.
-    """
-    @deprecated("instead of using `Sample`, create a register explicitly")
-    def __init__(self, expr, clocks, domain, *, src_loc_at=0):
-        super().__init__(src_loc_at=1 + src_loc_at)
-        self.value  = Value.cast(expr)
-        self.clocks = int(clocks)
-        self.domain = domain
-        if not isinstance(self.value, (Const, Signal, ClockSignal, ResetSignal, Initial)):
-            raise TypeError("Sampled value must be a signal or a constant, not {!r}"
-                            .format(self.value))
-        if self.clocks < 0:
-            raise ValueError("Cannot sample a value {} cycles in the future"
-                             .format(-self.clocks))
-        if not (self.domain is None or isinstance(self.domain, str)):
-            raise TypeError("Domain name must be a string or None, not {!r}"
-                            .format(self.domain))
-
-    def shape(self):
-        return self.value.shape()
-
-    def _rhs_signals(self):
-        return SignalSet((self,))
-
-    def __repr__(self):
-        return "(sample {!r} @ {}[{}])".format(
-            self.value, "<default>" if self.domain is None else self.domain, self.clocks)
-
-
-# TODO(amaranth-0.5): remove
-@deprecated("instead of using `Past`, create a register explicitly")
-def Past(expr, clocks=1, domain=None):
-    with _ignore_deprecated():
-        return Sample(expr, clocks, domain)
-
-
-# TODO(amaranth-0.5): remove
-@deprecated("instead of using `Stable`, create registers and comparisons explicitly")
-def Stable(expr, clocks=0, domain=None):
-    with _ignore_deprecated():
-        return Sample(expr, clocks + 1, domain) == Sample(expr, clocks, domain)
-
-
-# TODO(amaranth-0.5): remove
-@deprecated("instead of using `Rose`, create registers and comparisons explicitly")
-def Rose(expr, clocks=0, domain=None):
-    with _ignore_deprecated():
-        return ~Sample(expr, clocks + 1, domain) & Sample(expr, clocks, domain)
-
-
-# TODO(amaranth-0.5): remove
-@deprecated("instead of using `Fell`, create registers and comparisons explicitly")
-def Fell(expr, clocks=0, domain=None):
-    with _ignore_deprecated():
-        return Sample(expr, clocks + 1, domain) & ~Sample(expr, clocks, domain)
-
-
 @final
 class Initial(Value):
     """Start indicator, for model checking.
@@ -1626,7 +1562,7 @@ def shape(self):
         return Shape(1)
 
     def _rhs_signals(self):
-        return SignalSet((self,))
+        return SignalSet()
 
     def __repr__(self):
         return "(initial)"
@@ -1895,8 +1831,6 @@ def __init__(self, value):
         elif isinstance(self.value, ArrayProxy):
             self._hash = hash((ValueKey(self.value.index),
                               tuple(ValueKey(e) for e in self.value._iter_as_values())))
-        elif isinstance(self.value, Sample):
-            self._hash = hash((ValueKey(self.value.value), self.value.clocks, self.value.domain))
         elif isinstance(self.value, Initial):
             self._hash = 0
         else: # :nocov:
@@ -1942,10 +1876,6 @@ def __eq__(self, other):
                     all(ValueKey(a) == ValueKey(b)
                         for a, b in zip(self.value._iter_as_values(),
                                         other.value._iter_as_values())))
-        elif isinstance(self.value, Sample):
-            return (ValueKey(self.value.value) == ValueKey(other.value.value) and
-                    self.value.clocks == other.value.clocks and
-                    self.value.domain == self.value.domain)
         elif isinstance(self.value, Initial):
             return True
         else: # :nocov:
diff --git a/amaranth/hdl/dsl.py b/amaranth/hdl/dsl.py
index e6412ca08..6acd2fe7a 100644
--- a/amaranth/hdl/dsl.py
+++ b/amaranth/hdl/dsl.py
@@ -491,7 +491,6 @@ def domain_name(domain):
                     .format(domain_name(domain)))
 
             stmt._MustUse__used = True
-            stmt = SampleDomainInjector(domain)(stmt)
 
             for signal in stmt._lhs_signals():
                 if signal not in self._driving:
@@ -539,8 +538,7 @@ def elaborate(self, platform):
             fragment.add_subfragment(Fragment.get(self._named_submodules[name], platform), name)
         for submodule in self._anon_submodules:
             fragment.add_subfragment(Fragment.get(submodule, platform), None)
-        statements = SampleDomainInjector("sync")(self._statements)
-        fragment.add_statements(statements)
+        fragment.add_statements(self._statements)
         for signal, domain in self._driving.items():
             fragment.add_driver(signal, domain)
         fragment.add_domains(self._domains.values())
diff --git a/amaranth/hdl/ir.py b/amaranth/hdl/ir.py
index 5b2811f26..16aab52dd 100644
--- a/amaranth/hdl/ir.py
+++ b/amaranth/hdl/ir.py
@@ -506,11 +506,10 @@ def lca_of(fragu, fragv):
                 self.add_ports(sig, dir="i")
 
     def prepare(self, ports=None, missing_domain=lambda name: ClockDomain(name)):
-        from .xfrm import SampleLowerer, DomainLowerer
+        from .xfrm import DomainLowerer
 
-        fragment = SampleLowerer()(self)
-        new_domains = fragment._propagate_domains(missing_domain)
-        fragment = DomainLowerer()(fragment)
+        new_domains = self._propagate_domains(missing_domain)
+        fragment = DomainLowerer()(self)
         if ports is None:
             fragment._propagate_ports(ports=(), all_undef_as_ports=True)
         else:
diff --git a/amaranth/hdl/xfrm.py b/amaranth/hdl/xfrm.py
index 1ef8ab7da..acda1cc22 100644
--- a/amaranth/hdl/xfrm.py
+++ b/amaranth/hdl/xfrm.py
@@ -15,7 +15,6 @@
            "FragmentTransformer",
            "TransformedElaboratable",
            "DomainCollector", "DomainRenamer", "DomainLowerer",
-           "SampleDomainInjector", "SampleLowerer",
            "SwitchCleaner", "LHSGroupAnalyzer", "LHSGroupFilter",
            "ResetInserter", "EnableInserter"]
 
@@ -65,10 +64,6 @@ def on_Cat(self, value):
     def on_ArrayProxy(self, value):
         pass # :nocov:
 
-    @abstractmethod
-    def on_Sample(self, value):
-        pass # :nocov:
-
     @abstractmethod
     def on_Initial(self, value):
         pass # :nocov:
@@ -103,8 +98,6 @@ def on_value(self, value):
             new_value = self.on_Cat(value)
         elif type(value) is ArrayProxy:
             new_value = self.on_ArrayProxy(value)
-        elif type(value) is Sample:
-            new_value = self.on_Sample(value)
         elif type(value) is Initial:
             new_value = self.on_Initial(value)
         else:
@@ -153,9 +146,6 @@ def on_ArrayProxy(self, value):
         return ArrayProxy([self.on_value(elem) for elem in value._iter_as_values()],
                           self.on_value(value.index))
 
-    def on_Sample(self, value):
-        return Sample(self.on_value(value.value), value.clocks, value.domain)
-
     def on_Initial(self, value):
         return value
 
@@ -369,9 +359,6 @@ def on_ArrayProxy(self, value):
             self.on_value(elem)
         self.on_value(value.index)
 
-    def on_Sample(self, value):
-        self.on_value(value.value)
-
     def on_Initial(self, value):
         pass
 
@@ -509,81 +496,6 @@ def on_fragment(self, fragment):
         return new_fragment
 
 
-class SampleDomainInjector(ValueTransformer, StatementTransformer):
-    def __init__(self, domain):
-        self.domain = domain
-
-    @_ignore_deprecated
-    def on_Sample(self, value):
-        if value.domain is not None:
-            return value
-        return Sample(value.value, value.clocks, self.domain)
-
-    def __call__(self, stmts):
-        return self.on_statement(stmts)
-
-
-class SampleLowerer(FragmentTransformer, ValueTransformer, StatementTransformer):
-    def __init__(self):
-        self.initial = None
-        self.sample_cache = None
-        self.sample_stmts = None
-
-    def _name_reset(self, value):
-        if isinstance(value, Const):
-            return f"c${value.value}", value.value
-        elif isinstance(value, Signal):
-            return f"s${value.name}", value.reset
-        elif isinstance(value, ClockSignal):
-            return "clk", 0
-        elif isinstance(value, ResetSignal):
-            return "rst", 1
-        elif isinstance(value, Initial):
-            return "init", 0 # Past(Initial()) produces 0, 1, 0, 0, ...
-        else:
-            raise NotImplementedError # :nocov:
-
-    @_ignore_deprecated
-    def on_Sample(self, value):
-        if value in self.sample_cache:
-            return self.sample_cache[value]
-
-        sampled_value = self.on_value(value.value)
-        if value.clocks == 0:
-            sample = sampled_value
-        else:
-            assert value.domain is not None
-            sampled_name, sampled_reset = self._name_reset(value.value)
-            name = f"$sample${sampled_name}${value.domain}${value.clocks}"
-            sample = Signal.like(value.value, name=name, reset_less=True, reset=sampled_reset)
-            sample.attrs["amaranth.sample_reg"] = True
-
-            prev_sample = self.on_Sample(Sample(sampled_value, value.clocks - 1, value.domain))
-            if value.domain not in self.sample_stmts:
-                self.sample_stmts[value.domain] = []
-            self.sample_stmts[value.domain].append(sample.eq(prev_sample))
-
-        self.sample_cache[value] = sample
-        return sample
-
-    def on_Initial(self, value):
-        if self.initial is None:
-            self.initial = Signal(name="init")
-        return self.initial
-
-    def map_statements(self, fragment, new_fragment):
-        self.initial = None
-        self.sample_cache = ValueDict()
-        self.sample_stmts = OrderedDict()
-        new_fragment.add_statements(map(self.on_statement, fragment.statements))
-        for domain, stmts in self.sample_stmts.items():
-            new_fragment.add_statements(stmts)
-            for stmt in stmts:
-                new_fragment.add_driver(stmt.lhs, domain)
-        if self.initial is not None:
-            new_fragment.add_subfragment(Instance("$initstate", o_Y=self.initial))
-
-
 class SwitchCleaner(StatementVisitor):
     def on_ignore(self, stmt):
         return stmt
diff --git a/amaranth/sim/_pyrtl.py b/amaranth/sim/_pyrtl.py
index a74006027..bb31cdfba 100644
--- a/amaranth/sim/_pyrtl.py
+++ b/amaranth/sim/_pyrtl.py
@@ -103,9 +103,6 @@ def on_AnyConst(self, value):
     def on_AnySeq(self, value):
         raise NotImplementedError # :nocov:
 
-    def on_Sample(self, value):
-        raise NotImplementedError # :nocov:
-
     def on_Initial(self, value):
         raise NotImplementedError # :nocov:
 
diff --git a/docs/changes.rst b/docs/changes.rst
index 93716d771..0f718f59c 100644
--- a/docs/changes.rst
+++ b/docs/changes.rst
@@ -13,6 +13,7 @@ Language changes
 .. currentmodule:: amaranth.hdl
 
 * Removed: (deprecated in 0.4) :meth:`Const.normalize`. (`RFC 5`_)
+* Removed: (deprecated in 0.4) :class:`ast.Sample`, :class:`ast.Past`, :class:`ast.Stable`, :class:`ast.Rose`, :class:`ast.Fell`.
 
 
 Standard library changes
diff --git a/tests/test_hdl_ast.py b/tests/test_hdl_ast.py
index 56dfca3d1..625e0e884 100644
--- a/tests/test_hdl_ast.py
+++ b/tests/test_hdl_ast.py
@@ -894,7 +894,7 @@ def test_repr(self):
     def test_cast(self):
         c = Cat(1, 0)
         self.assertEqual(repr(c), "(cat (const 1'd1) (const 1'd0))")
-    
+
     def test_str_wrong(self):
         with self.assertRaisesRegex(TypeError,
                 r"^Object 'foo' cannot be converted to an Amaranth value$"):
@@ -1382,39 +1382,6 @@ class EnumD(Enum):
         self.assertFalse(isinstance(EnumD.A, ValueLike))
 
 
-class SampleTestCase(FHDLTestCase):
-    @_ignore_deprecated
-    def test_const(self):
-        s = Sample(1, 1, "sync")
-        self.assertEqual(s.shape(), unsigned(1))
-
-    @_ignore_deprecated
-    def test_signal(self):
-        s1 = Sample(Signal(2), 1, "sync")
-        self.assertEqual(s1.shape(), unsigned(2))
-        s2 = Sample(ClockSignal(), 1, "sync")
-        s3 = Sample(ResetSignal(), 1, "sync")
-
-    @_ignore_deprecated
-    def test_wrong_value_operator(self):
-        with self.assertRaisesRegex(TypeError,
-                (r"^Sampled value must be a signal or a constant, not "
-                r"\(\+ \(sig \$signal\) \(const 1'd1\)\)$")):
-            Sample(Signal() + 1, 1, "sync")
-
-    @_ignore_deprecated
-    def test_wrong_clocks_neg(self):
-        with self.assertRaisesRegex(ValueError,
-                r"^Cannot sample a value 1 cycles in the future$"):
-            Sample(Signal(), -1, "sync")
-
-    @_ignore_deprecated
-    def test_wrong_domain(self):
-        with self.assertRaisesRegex(TypeError,
-                r"^Domain name must be a string or None, not 0$"):
-            Sample(Signal(), 1, 0)
-
-
 class InitialTestCase(FHDLTestCase):
     def test_initial(self):
         i = Initial()
diff --git a/tests/test_hdl_dsl.py b/tests/test_hdl_dsl.py
index 9fc210ff5..9558ef61c 100644
--- a/tests/test_hdl_dsl.py
+++ b/tests/test_hdl_dsl.py
@@ -133,25 +133,6 @@ def test_reset_signal(self):
         )
         """)
 
-    @_ignore_deprecated
-    def test_sample_domain(self):
-        m = Module()
-        i = Signal()
-        o1 = Signal()
-        o2 = Signal()
-        o3 = Signal()
-        m.d.sync += o1.eq(Past(i))
-        m.d.pix  += o2.eq(Past(i))
-        m.d.pix  += o3.eq(Past(i, domain="sync"))
-        f = m.elaborate(platform=None)
-        self.assertRepr(f.statements, """
-        (
-            (eq (sig o1) (sample (sig i) @ sync[1]))
-            (eq (sig o2) (sample (sig i) @ pix[1]))
-            (eq (sig o3) (sample (sig i) @ sync[1]))
-        )
-        """)
-
     def test_If(self):
         m = Module()
         with m.If(self.s1):
diff --git a/tests/test_hdl_xfrm.py b/tests/test_hdl_xfrm.py
index f450d005d..e3ff03b51 100644
--- a/tests/test_hdl_xfrm.py
+++ b/tests/test_hdl_xfrm.py
@@ -210,54 +210,6 @@ def test_lower_wrong_reset_less_domain(self):
             DomainLowerer()(f)
 
 
-class SampleLowererTestCase(FHDLTestCase):
-    def setUp(self):
-        self.i = Signal()
-        self.o1 = Signal()
-        self.o2 = Signal()
-        self.o3 = Signal()
-
-    @_ignore_deprecated
-    def test_lower_signal(self):
-        f = Fragment()
-        f.add_statements(
-            self.o1.eq(Sample(self.i, 2, "sync")),
-            self.o2.eq(Sample(self.i, 1, "sync")),
-            self.o3.eq(Sample(self.i, 1, "pix")),
-        )
-
-        f = SampleLowerer()(f)
-        self.assertRepr(f.statements, """
-        (
-            (eq (sig o1) (sig $sample$s$i$sync$2))
-            (eq (sig o2) (sig $sample$s$i$sync$1))
-            (eq (sig o3) (sig $sample$s$i$pix$1))
-            (eq (sig $sample$s$i$sync$1) (sig i))
-            (eq (sig $sample$s$i$sync$2) (sig $sample$s$i$sync$1))
-            (eq (sig $sample$s$i$pix$1) (sig i))
-        )
-        """)
-        self.assertEqual(len(f.drivers["sync"]), 2)
-        self.assertEqual(len(f.drivers["pix"]), 1)
-
-    @_ignore_deprecated
-    def test_lower_const(self):
-        f = Fragment()
-        f.add_statements(
-            self.o1.eq(Sample(1, 2, "sync")),
-        )
-
-        f = SampleLowerer()(f)
-        self.assertRepr(f.statements, """
-        (
-            (eq (sig o1) (sig $sample$c$1$sync$2))
-            (eq (sig $sample$c$1$sync$1) (const 1'd1))
-            (eq (sig $sample$c$1$sync$2) (sig $sample$c$1$sync$1))
-        )
-        """)
-        self.assertEqual(len(f.drivers["sync"]), 2)
-
-
 class SwitchCleanerTestCase(FHDLTestCase):
     def test_clean(self):
         a = Signal()
diff --git a/tests/test_sim.py b/tests/test_sim.py
index 60fd58e3e..19e493b25 100644
--- a/tests/test_sim.py
+++ b/tests/test_sim.py
@@ -911,53 +911,6 @@ def process():
             sim.add_clock(1e-6)
             sim.add_sync_process(process)
 
-    @_ignore_deprecated
-    def test_sample_helpers(self):
-        m = Module()
-        s = Signal(2)
-        def mk(x):
-            y = Signal.like(x)
-            m.d.comb += y.eq(x)
-            return y
-        p0, r0, f0, s0 = mk(Past(s, 0)), mk(Rose(s)),    mk(Fell(s)),    mk(Stable(s))
-        p1, r1, f1, s1 = mk(Past(s)),    mk(Rose(s, 1)), mk(Fell(s, 1)), mk(Stable(s, 1))
-        p2, r2, f2, s2 = mk(Past(s, 2)), mk(Rose(s, 2)), mk(Fell(s, 2)), mk(Stable(s, 2))
-        p3, r3, f3, s3 = mk(Past(s, 3)), mk(Rose(s, 3)), mk(Fell(s, 3)), mk(Stable(s, 3))
-        with self.assertSimulation(m) as sim:
-            def process_gen():
-                yield s.eq(0b10)
-                yield
-                yield
-                yield s.eq(0b01)
-                yield
-            def process_check():
-                yield
-                yield
-                yield
-
-                self.assertEqual((yield p0), 0b01)
-                self.assertEqual((yield p1), 0b10)
-                self.assertEqual((yield p2), 0b10)
-                self.assertEqual((yield p3), 0b00)
-
-                self.assertEqual((yield s0), 0b0)
-                self.assertEqual((yield s1), 0b1)
-                self.assertEqual((yield s2), 0b0)
-                self.assertEqual((yield s3), 0b1)
-
-                self.assertEqual((yield r0), 0b01)
-                self.assertEqual((yield r1), 0b00)
-                self.assertEqual((yield r2), 0b10)
-                self.assertEqual((yield r3), 0b00)
-
-                self.assertEqual((yield f0), 0b10)
-                self.assertEqual((yield f1), 0b00)
-                self.assertEqual((yield f2), 0b00)
-                self.assertEqual((yield f3), 0b00)
-            sim.add_clock(1e-6)
-            sim.add_sync_process(process_gen)
-            sim.add_sync_process(process_check)
-
     def test_vcd_wrong_nonzero_time(self):
         s = Signal()
         m = Module()