core: store blocks as doubly-linked list on Region [2/2]

tests/test_linked_list.py

@@ -1,6 +1,8 @@
+import pytest
+
 from xdsl.dialects.arith import Constant
 from xdsl.dialects.builtin import i32
-from xdsl.ir import Block
+from xdsl.ir import Block, Region
 
 
 def test_block_insert():
@@ -73,3 +75,103 @@ def test_block_insert():
     assert e.prev_op is d
 
     assert list(block.ops) == [a, b, c, d, e]
+
+
+def test_region_insert():
+    a = Block((Constant.from_int_and_width(1, i32),))
+    b = Block((Constant.from_int_and_width(2, i32),))
+    c = Block((Constant.from_int_and_width(3, i32),))
+    d = Block((Constant.from_int_and_width(4, i32),))
+    e = Block((Constant.from_int_and_width(5, i32),))
+
+    region = Region()
+
+    assert not region.blocks
+
+    assert region.first_block is None
+    assert region.last_block is None
+
+    assert list(region.blocks) == []
+
+    region.add_block(a)
+
+    assert region.blocks
+
+    assert region.first_block is a
+    assert region.last_block is a
+
+    assert list(region.blocks) == [a]
+
+    region.add_block(c)
+
+    assert region.first_block is a
+    assert region.last_block is c
+
+    assert a.next_block is c
+    assert c.prev_block is a
+
+    assert list(region.blocks) == [a, c]
+
+    region.insert_block_after(b, a)
+
+    assert region.first_block is a
+    assert region.last_block is c
+
+    assert a.next_block is b
+    assert b.prev_block is a
+
+    assert b.next_block is c
+    assert c.prev_block is b
+
+    assert list(region.blocks) == [a, b, c]
+
+    region.add_block(e)
+
+    assert region.first_block is a
+    assert region.last_block is e
+
+    assert c.next_block is e
+    assert e.prev_block is c
+
+    assert list(region.blocks) == [a, b, c, e]
+
+    region.insert_block_before(d, e)
+
+    assert region.first_block is a
+    assert region.last_block is e
+
+    assert c.next_block is d
+    assert d.prev_block is c
+
+    assert d.next_block is e
+    assert e.prev_block is d
+
+    assert list(region.blocks) == [a, b, c, d, e]
+
+
+def test_region_indexing():
+    a = Block((Constant.from_int_and_width(1, i32),))
+    b = Block((Constant.from_int_and_width(2, i32),))
+    c = Block((Constant.from_int_and_width(3, i32),))
+    d = Block((Constant.from_int_and_width(4, i32),))
+    e = Block((Constant.from_int_and_width(5, i32),))
+
+    region = Region((a, b, c, d, e))
+
+    assert region.blocks[0] == a
+    assert region.blocks[1] == b
+    assert region.blocks[2] == c
+    assert region.blocks[3] == d
+    assert region.blocks[4] == e
+
+    with pytest.raises(IndexError):
+        region.blocks[5]
+
+    assert region.blocks[-1] == e
+    assert region.blocks[-2] == d
+    assert region.blocks[-3] == c
+    assert region.blocks[-4] == b
+    assert region.blocks[-5] == a
+
+    with pytest.raises(IndexError):
+        region.blocks[-6]

xdsl/dialects/builtin.py

@@ -1427,7 +1427,7 @@ def parse(cls, parser: Parser) -> ModuleOp:
         region = parser.parse_region()
 
         # Add a block if the region is empty
-        if len(region.blocks) == 0:
+        if not region.blocks:
             region.add_block(Block())
 
         return ModuleOp(region, attributes)

xdsl/dialects/riscv_cf.py

@@ -130,12 +130,7 @@ def verify_(self) -> None:
         if parent_region is None:
             return
 
-        # TODO: use next_block to check this instead
-        blocks = tuple(parent_region.blocks)
-        this_index = blocks.index(parent_block)
-        else_index = blocks.index(self.else_block)
-
-        if this_index + 1 != else_index:
+        if parent_block.next_block is not self.else_block:
             raise VerifyException(
                 "riscv_cf branch op else block must be immediately after op"
             )

xdsl/dialects/x86/ops.py

@@ -2051,12 +2051,7 @@ def verify_(self) -> None:
         if parent_region is None:
             return
 
-        # TODO: replace check with next_block later
-        blocks = tuple(parent_region.blocks)
-        this_index = blocks.index(parent_block)
-        else_index = blocks.index(self.else_block)
-
-        if this_index + 1 != else_index:
+        if parent_block.next_block is not self.else_block:
             raise VerifyException("else block must be immediately after op")
 
     def assembly_line_args(self) -> tuple[AssemblyInstructionArg, ...]: