Merge pull request #1796 from iamdefinitelyahuman/bitwise-ops

Implement SHL/SHR for bitshifting

docs/compiling-a-contract.rst

@@ -128,7 +128,7 @@ The following is a list of supported EVM versions, and changes in the compiler i
 - ``byzantium``
    - The oldest EVM version supported by Vyper.
 - ``constantinople``
-   - The compiler behaves the same way as with byzantium.
+   - ``shift`` makes use of ``SHL``/``SHR`` opcodes.
 - ``petersburg``
    - The compiler behaves the same way as with consantinople.
 - ``istanbul`` **(default)**

tests/parser/functions/test_bitwise.py

@@ -1,5 +1,13 @@
-def test_test_bitwise(get_contract_with_gas_estimation):
-    test_bitwise = """
+import pytest
+
+from vyper.compiler import (
+    compile_code,
+)
+from vyper.opcodes import (
+    EVM_VERSIONS,
+)
+
+code = """
 @public
 def _bitwise_and(x: uint256, y: uint256) -> uint256:
     return bitwise_and(x, y)
@@ -21,7 +29,21 @@ def _shift(x: uint256, y: int128) -> uint256:
     return shift(x, y)
     """
 
-    c = get_contract_with_gas_estimation(test_bitwise)
+
+@pytest.mark.parametrize('evm_version', list(EVM_VERSIONS))
+def test_bitwise_opcodes(evm_version):
+    opcodes = compile_code(code, ['opcodes'], evm_version=evm_version)['opcodes']
+    if evm_version == "byzantium":
+        assert "SHL" not in opcodes
+        assert "SHR" not in opcodes
+    else:
+        assert "SHL" in opcodes
+        assert "SHR" in opcodes
+
+
+@pytest.mark.parametrize('evm_version', list(EVM_VERSIONS))
+def test_test_bitwise(get_contract_with_gas_estimation, evm_version):
+    c = get_contract_with_gas_estimation(code, evm_version=evm_version)
     x = 126416208461208640982146408124
     y = 7128468721412412459
     assert c._bitwise_and(x, y) == (x & y)
@@ -37,4 +59,19 @@ def _shift(x: uint256, y: int128) -> uint256:
     assert c._shift(x, -3) == x // 8
     assert c._shift(x, -256) == 0
 
-    print("Passed bitwise operation tests")
+
+@pytest.mark.parametrize('evm_version', list(EVM_VERSIONS))
+def test_literals(get_contract, evm_version):
+    code = """
+@public
+def left(x: uint256) -> uint256:
+    return shift(x, -3)
+
+@public
+def right(x: uint256) -> uint256:
+    return shift(x, 3)
+    """
+
+    c = get_contract(code, evm_version=evm_version)
+    assert c.left(80) == 10
+    assert c.right(80) == 640

vyper/functions/functions.py

@@ -8,6 +8,9 @@
     StructureException,
     TypeMismatchException,
 )
+from vyper.opcodes import (
+    version_check,
+)
 from vyper.parser.expr import (
     Expr,
 )
@@ -1063,19 +1066,35 @@ def bitwise_not(expr, args, kwargs, context):
 
 @signature('uint256', 'int128')
 def shift(expr, args, kwargs, context):
+
+    if args[1].typ.is_literal:
+        shift_abs = abs(args[1].value)
+    else:
+        shift_abs = ['sub', 0, '_s']
+
+    if version_check(begin="constantinople"):
+        left_shift = ['shl', '_s', '_v']
+        right_shift = ['shr', shift_abs, '_v']
+    else:
+        # If second argument is positive, left-shift so multiply by a power of two
+        # If it is negative, divide by a power of two
+        # node that if the abs of the second argument >= 256, then in the EVM
+        # 2**(second arg) = 0, and multiplying OR dividing by 0 gives 0
+        left_shift = ['mul', '_v', ['exp', 2, '_s']]
+        right_shift = ['div', '_v', ['exp', 2, shift_abs]]
+
+    if not args[1].typ.is_literal:
+        node_list = ['if', ['slt', '_s', 0], right_shift, left_shift]
+    elif args[1].value >= 0:
+        node_list = left_shift
+    else:
+        node_list = right_shift
+
     return LLLnode.from_list(
         [
             'with', '_v', args[0], [
-                'with', '_s', args[1], [
-                    # If second argument is positive, left-shift so multiply by a power of two
-                    # If it is negative, divide by a power of two
-                    # node that if the abs of the second argument >= 256, then in the EVM
-                    # 2**(second arg) = 0, and multiplying OR dividing by 0 gives 0
-                    'if',
-                    ['slt', '_s', 0],
-                    ['div', '_v', ['exp', 2, ['sub', 0, '_s']]],
-                    ['mul', '_v', ['exp', 2, '_s']]
-                ],
+                'with', '_s', args[1],
+                    node_list,
             ],
         ],
         typ=BaseType('uint256'),