From 7c52910dc59d28c7429f88154b10fad05a4f4de2 Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Sat, 11 Jul 2015 18:46:37 +0300
Subject: [PATCH] Add a basic SSA IR.

---
 artiq/compiler/ir.py | 319 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 319 insertions(+)
 create mode 100644 artiq/compiler/ir.py

diff --git a/artiq/compiler/ir.py b/artiq/compiler/ir.py
new file mode 100644
index 000000000..10c926ae7
--- /dev/null
+++ b/artiq/compiler/ir.py
@@ -0,0 +1,319 @@
+"""
+The :mod:`ir` module contains the intermediate representation
+of the ARTIQ compiler.
+"""
+
+from . import types, builtins
+
+# Generic SSA IR classes
+
+def escape_name(name):
+    if all([isalnum(x) or x == "." for x in name]):
+        return name
+    else:
+        return "\"{}\"".format(name.replace("\"", "\\\""))
+
+class TSSABasicBlock(types.TMono):
+    def __init__(self):
+        super().__init__("ssa.basic_block")
+
+class TSSAOption(types.TMono):
+    def __init__(self, inner):
+        super().__init__("ssa.option", {"inner": inner})
+
+class Value:
+    """
+    An SSA value that keeps track of its uses.
+
+    :ivar type: (:class:`.types.Type`) type of this value
+    :ivar uses: (list of :class:`Value`) values that use this value
+    """
+
+    def __init__(self, typ=builtins.TNone()):
+        self.uses, self.type = set(), typ
+
+    def replace_all_uses_with(self, value):
+        for user in self.uses:
+            user.replace_uses_of(self, value)
+
+class NamedValue(Value):
+    """
+    An SSA value that has a name.
+
+    :ivar name: (string) name of this value
+    :ivar function: (:class:`Function`) function containing this value
+    """
+
+    def __init__(self, typ=builtins.TNone(), name=""):
+        super().__init__(typ)
+        self.name, self.function = name, None
+
+    def set_name(self, new_name):
+        if self.function is not None:
+            self.function._remove_name(self.name)
+            self.name = self.function._add_name(new_name)
+        else:
+            self.name = new_name
+
+    def _set_function(self, new_function):
+        if self.function != new_function:
+            if self.function is not None:
+                self.function._remove_name(self.name)
+            self.function = new_function
+            if self.function is not None:
+                self.name = self.function._add_name(self.name)
+
+    def _detach(self):
+        self.function = None
+
+    def as_operand(self):
+        return "{} %{}".format(types.TypePrinter().name(self.type),
+                               escape_name(self.name))
+
+class User(NamedValue):
+    """
+    An SSA value that has operands.
+
+    :ivar operands: (list of :class:`Value`) operands of this value
+    """
+
+    def __init__(self, typ=builtins.TNone(), name="", operands=[]):
+        super().__init__(typ, name)
+        self.operands = []
+        self.set_operands(operands)
+
+    def set_operands(self, new_operands):
+        for operand in self.operands:
+            operand.uses.remove(self)
+        self.operands = new_operands
+        for operand in self.operands:
+            operand.uses.add(self)
+
+    def drop_references(self):
+        self.set_operands([])
+
+    def replace_uses_of(self, value, replacement):
+        assert value in operands
+
+        for index, operand in enumerate(operands):
+            if operand == value:
+                operands[index] = replacement
+
+        value.uses.remove(self)
+        replacement.uses.add(self)
+
+class Instruction(User):
+    """
+    An SSA instruction.
+    """
+
+    def __init__(self, typ=builtins.TNone(), name="", operands=[]):
+        super().__init__(typ, name, operands)
+        self.basic_block = None
+
+    def set_basic_block(self, new_basic_block):
+        self.basic_block = new_basic_block
+        if self.basic_block is not None:
+            self._set_function(self.basic_block.function)
+        else:
+            self._set_function(None)
+
+    def opcode(self):
+        """String representation of the opcode."""
+        return "???"
+
+    def _detach(self):
+        self.set_basic_block(None)
+
+    def remove_from_parent(self):
+        if self.basic_block is not None:
+            self.basic_block.remove(self)
+
+    def erase(self):
+        self.remove_from_parent()
+        self.drop_references()
+
+    def replace_with(self, value):
+        self.replace_all_uses_with(value)
+        if isinstance(value, Instruction):
+            self.basic_block.replace(self, value)
+            self.drop_references()
+        else:
+            self.erase()
+
+    def __str__(self):
+        if builtins.is_none(self.type):
+            prefix = ""
+        else:
+            prefix = "%{} = {} ".format(escape_name(self.name),
+                                        types.TypePrinter().name(self.type))
+
+        if any(self.operands):
+            return "{} {} {}".format(prefix, self.opcode(),
+                ", ".join([operand.as_operand() for operand in self.operands]))
+        else:
+            return "{} {}".format(prefix, self.opcode())
+
+class Phi(Instruction):
+    """
+    An SSA instruction that joins data flow.
+    """
+
+    def opcode(self):
+        return "phi"
+
+    def incoming(self):
+        operand_iter = iter(self.operands)
+        while True:
+            yield next(operand_iter), next(operand_iter)
+
+    def incoming_blocks(self):
+        (block for (block, value) in self.incoming())
+
+    def incoming_values(self):
+        (value for (block, value) in self.incoming())
+
+    def incoming_value_for_block(self, target_block):
+        for (block, value) in self.incoming():
+            if block == target_block:
+                return value
+        assert False
+
+    def add_incoming(self, value, block):
+        assert value.type == self.type
+        self.operands.append(value)
+        self.operands.append(block)
+
+    def __str__(self):
+        if builtins.is_none(self.type):
+            prefix = ""
+        else:
+            prefix = "%{} = {} ".format(escape_name(self.name),
+                                        types.TypePrinter().name(self.type))
+
+        if any(self.operands):
+            operand_list = ["%{} => %{}".format(escape_name(block.name), escape_name(value.name))
+                            for operand in self.operands]
+            return "{} {} [{}]".format(prefix, self.opcode(), ", ".join(operand_list))
+
+class Terminator(Instruction):
+    """
+    An SSA instruction that performs control flow.
+    """
+
+    def successors(self):
+        [operand for operand in self.operands if isinstance(operand, BasicBlock)]
+
+class BasicBlock(NamedValue):
+    """
+    A block of instructions with no control flow inside it.
+
+    :ivar instructions: (list of :)
+    """
+
+    def __init__(self, name="", instructions=[]):
+        super().__init__(TSSABasicBlock(), name)
+        self.instructions = []
+        self.set_instructions(instructions)
+
+    def remove_from_parent(self):
+        if self.function is not None:
+            self.function.remove(self)
+
+    def prepend(self, insn):
+        insn.set_basic_block(self)
+        self.instructions.insert(0, insn)
+
+    def append(self, insn):
+        insn.set_basic_block(self)
+        self.instructions.append(insn)
+
+    def index(self, insn):
+        return self.instructions.index(insn)
+
+    def insert(self, before, insn):
+        insn.set_basic_block(self)
+        self.instructions.insert(self.index(before), insn)
+
+    def remove(self, insn):
+        insn._detach()
+        self.instructions.remove(insn)
+
+    def replace(self, insn, replacement):
+        self.insert(insn, replacement)
+        self.remove(insn)
+
+    def terminator(self):
+        assert isinstance(self.instructions[-1], Terminator)
+        return self.instructions[-1]
+
+    def successors(self):
+        return self.terminator().successors()
+
+    def predecessors(self):
+        assert self.function is not None
+        self.function.predecessors_of(self)
+
+    def __str__(self):
+        lines = ["{}:".format(escape_name(self.name))]
+        for insn in self.instructions:
+            lines.append(str(insn))
+        return "\n".join(lines)
+
+class Argument(NamedValue):
+    """
+    A function argument.
+    """
+
+    def __str__(self):
+        return self.as_operand()
+
+class Function(Value):
+    """
+    A function containing SSA IR.
+    """
+
+    def __init__(self, typ, name, arguments):
+        self.type, self.name, self.arguments = typ, name, []
+        self.set_arguments(arguments)
+        self.basic_blocks = set()
+        self.names = set()
+
+    def _remove_name(self, name):
+        self.names.remove(name)
+
+    def _add_name(self, base_name):
+        name, counter = base_name, 1
+        while name in self.names or name == "":
+            if base_name == "":
+                name = str(counter)
+            else:
+                name = "{}.{}".format(name, counter)
+            counter += 1
+
+        self.names.add(name)
+        return name
+
+    def set_arguments(self, new_arguments):
+        for argument in self.arguments:
+            argument._set_function(None)
+        self.arguments = new_arguments
+        for argument in self.arguments:
+            argument._set_function(self)
+
+    def add(self, basic_block):
+        basic_block._set_function(self)
+        self.basic_blocks.add(basic_blocks)
+
+    def remove(self, basic_block):
+        basic_block._detach()
+        self.basic_block.remove(basic_block)
+
+    def predecessors_of(self, successor):
+        set(block for block in self.basic_blocks if successor in block.successors())
+
+    def as_operand(self):
+        return "{} @{}".format(types.TypePrinter().name(self.type),
+                               escape_name(self.name))
+
+# Python-specific SSA IR classes