transforms.interleaver: unroll loops.

artiq/compiler/algorithms/__init__.py

@@ -1 +1,2 @@
 from .inline import inline
+from .unroll import unroll

artiq/compiler/algorithms/unroll.py

@@ -0,0 +1,97 @@
+"""
+:func:`unroll` unrolls a loop instruction in ARTIQ IR.
+The loop's trip count must be constant.
+The loop body must not have any control flow instructions
+except for one branch back to the loop head.
+The loop body must be executed if the condition to which
+the instruction refers is true.
+"""
+
+from .. import types, builtins, iodelay, ir
+from ..analyses import domination
+
+def _get_body_blocks(root, limit):
+    postorder = []
+
+    visited = set()
+    def visit(block):
+        visited.add(block)
+        for next_block in block.successors():
+            if next_block not in visited and next_block is not limit:
+                visit(next_block)
+        postorder.append(block)
+
+    visit(root)
+
+    postorder.reverse()
+    return postorder
+
+def unroll(loop_insn):
+    loop_head = loop_insn.basic_block
+    function  = loop_head.function
+    assert isinstance(loop_insn, ir.Loop)
+    assert len(loop_head.predecessors()) == 2
+    assert len(loop_insn.if_false().predecessors()) == 1
+    assert iodelay.is_const(loop_insn.trip_count)
+
+    trip_count = loop_insn.trip_count.fold().value
+    if trip_count == 0:
+        loop_insn.replace_with(ir.Branch(loop_insn.if_false()))
+        return
+
+    source_blocks = _get_body_blocks(loop_insn.if_true(), loop_head)
+    source_indvar = loop_insn.induction_variable()
+    source_tail   = loop_insn.if_false()
+    unroll_target = loop_head
+    for n in range(trip_count):
+        value_map = {source_indvar: ir.Constant(n, source_indvar.type)}
+
+        for source_block in source_blocks:
+            target_block = ir.BasicBlock([], "u{}.{}".format(n, source_block.name))
+            function.add(target_block)
+            value_map[source_block] = target_block
+
+        def mapper(value):
+            if isinstance(value, ir.Constant):
+                return value
+            elif value in value_map:
+                return value_map[value]
+            else:
+                return value
+
+        for source_block in source_blocks:
+            target_block = value_map[source_block]
+            for source_insn in source_block.instructions:
+                if isinstance(source_insn, ir.Phi):
+                    target_insn = ir.Phi()
+                else:
+                    target_insn = source_insn.copy(mapper)
+                    target_insn.name = "u{}.{}".format(n, source_insn.name)
+                target_block.append(target_insn)
+                value_map[source_insn] = target_insn
+
+        for source_block in source_blocks:
+            for source_insn in source_block.instructions:
+                if isinstance(source_insn, ir.Phi):
+                    target_insn = value_map[source_insn]
+                    for block, value in source_insn.incoming():
+                        target_insn.add_incoming(value_map[value], value_map[block])
+
+        assert isinstance(unroll_target.terminator(), (ir.Branch, ir.Loop))
+        unroll_target.terminator().replace_with(ir.Branch(value_map[source_blocks[0]]))
+        unroll_target = value_map[source_blocks[-1]]
+
+    assert isinstance(unroll_target.terminator(), ir.Branch)
+    assert len(source_blocks[-1].successors()) == 1
+    unroll_target.terminator().replace_with(ir.Branch(source_tail))
+
+    for source_block in reversed(source_blocks):
+        for source_insn in reversed(source_block.instructions):
+            for use in set(source_insn.uses):
+                if isinstance(use, ir.Phi):
+                    assert use.basic_block == loop_head
+                    use.remove_incoming_value(source_insn)
+            source_insn.erase()
+
+    for source_block in reversed(source_blocks):
+        source_block.erase()

artiq/compiler/ir.py

@@ -1371,17 +1371,21 @@ class Loop(Terminator):
     :param trip_count: (:class:`iodelay.Expr`) expression
     :param substs: (dict of str to :class:`Value`)
         SSA values corresponding to iodelay variable names
+    :param indvar: (:class:`Phi`)
+        phi node corresponding to the induction SSA value,
+        which advances from ``0`` to ``trip_count - 1``
     :param cond: (:class:`Value`) branch condition
     :param if_true: (:class:`BasicBlock`) branch target if condition is truthful
     :param if_false: (:class:`BasicBlock`) branch target if condition is falseful
     """
-    def __init__(self, trip_count, substs, cond, if_true, if_false, name=""):
+    def __init__(self, trip_count, substs, indvar, cond, if_true, if_false, name=""):
         for var_name in substs: assert isinstance(var_name, str)
+        assert isinstance(indvar, Phi)
         assert isinstance(cond, Value)
         assert builtins.is_bool(cond.type)
         assert isinstance(if_true, BasicBlock)
         assert isinstance(if_false, BasicBlock)
-        super().__init__([cond, if_true, if_false, *substs.values()], builtins.TNone(), name)
+        super().__init__([indvar, cond, if_true, if_false, *substs.values()], builtins.TNone(), name)
         self.trip_count = trip_count
         self.var_names = list(substs.keys())
 
@@ -1391,17 +1395,20 @@ class Loop(Terminator):
         self_copy.var_names = list(self.var_names)
         return self_copy
 
-    def condition(self):
+    def induction_variable(self):
         return self.operands[0]
 
-    def if_true(self):
+    def condition(self):
         return self.operands[1]
 
-    def if_false(self):
+    def if_true(self):
         return self.operands[2]
 
+    def if_false(self):
+        return self.operands[3]
+
     def substs(self):
-        return {key: value for key, value in zip(self.var_names, self.operands[3:])}
+        return {key: value for key, value in zip(self.var_names, self.operands[4:])}
 
     def _operands_as_string(self, type_printer):
         substs = self.substs()
@@ -1409,8 +1416,8 @@ class Loop(Terminator):
         for var_name in substs:
             substs_as_strings.append("{} = {}".format(var_name, substs[var_name]))
         result = "[{}]".format(", ".join(substs_as_strings))
-        result += ", {}, {}, {}".format(*list(map(lambda value: value.as_operand(type_printer),
-                                                  self.operands[0:3])))
+        result += ", indvar {}, if {}, {}, {}".format(
+            *list(map(lambda value: value.as_operand(type_printer), self.operands[0:4])))
         return result
 
     def opcode(self):

artiq/compiler/module.py

@@ -73,6 +73,7 @@ class Module:
         dead_code_eliminator.process(self.artiq_ir)
         local_access_validator.process(self.artiq_ir)
         interleaver.process(self.artiq_ir)
+        dead_code_eliminator.process(self.artiq_ir)
 
     def build_llvm_ir(self, target):
         """Compile the module to LLVM IR for the specified target."""

artiq/compiler/transforms/artiq_ir_generator.py

@@ -525,7 +525,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
             if node.trip_count is not None:
                 substs = {var_name: self.current_args[var_name]
                           for var_name in node.trip_count.free_vars()}
-                head.append(ir.Loop(node.trip_count, substs, cond, body, else_tail))
+                head.append(ir.Loop(node.trip_count, substs, phi, cond, body, else_tail))
             else:
                 head.append(ir.BranchIf(cond, body, else_tail))
             if not post_body.is_terminated():

artiq/compiler/transforms/interleaver.py

@@ -7,7 +7,7 @@ from pythonparser import diagnostic
 
 from .. import types, builtins, ir, iodelay
 from ..analyses import domination
-from ..algorithms import inline
+from ..algorithms import inline, unroll
 
 def delay_free_subgraph(root, limit):
     visited = set()
@@ -152,6 +152,11 @@ class Interleaver:
                             source_terminator.interval = iodelay.Const(target_time_delta)
                         else:
                             source_terminator.replace_with(ir.Branch(source_terminator.target()))
+                elif isinstance(source_terminator, ir.Loop):
+                    unroll(source_terminator)
+
+                    postdom_tree = domination.PostDominatorTree(func)
+                    continue
                 else:
                     assert False
 

lit-test/test/interleaving/unrolling.py

@@ -0,0 +1,23 @@
+# RUN: %python -m artiq.compiler.testbench.jit %s >%t
+# RUN: OutputCheck %s --file-to-check=%t
+
+with parallel:
+    for x in range(10):
+        delay_mu(1)
+        print("a", x)
+    with sequential:
+        delay_mu(5)
+        print("c")
+    with sequential:
+        delay_mu(3)
+        print("b")
+
+# CHECK-L: a 0
+# CHECK-L: a 1
+# CHECK-L: a 2
+# CHECK-L: b
+# CHECK-L: a 3
+# CHECK-L: a 4
+# CHECK-L: c
+# CHECK-L: a 5
+# CHECK-L: a 6