[mypyc] Add faster primitive for string equality (#19402)

This speeds up self check by ~1.4%.  String equality is one of the top
five most common primitive function calls in self check.

We previously used a string comparison primitive that calculated the
relative order of two strings. Usually we only care about equality,
which we can do quicker since we can fast path using a length check,
for example.

I checked the CPython implementation of string equality in 3.9 (lowest
supported Python version) and 3.13, and both of them had a fast path
based on string object kind, and equality checks overall had the same
semantics.

Current CPython implementation:
https://github.com/python/cpython/blob/main/Objects/stringlib/eq.h

Tests for this were added in #19401.

Author: JukkaL

mypyc/irbuild/ll_builder.py

@@ -175,7 +175,12 @@
     unary_ops,
 )
 from mypyc.primitives.set_ops import new_set_op
-from mypyc.primitives.str_ops import str_check_if_true, str_ssize_t_size_op, unicode_compare
+from mypyc.primitives.str_ops import (
+    str_check_if_true,
+    str_eq,
+    str_ssize_t_size_op,
+    unicode_compare,
+)
 from mypyc.primitives.tuple_ops import list_tuple_op, new_tuple_op, new_tuple_with_length_op
 from mypyc.rt_subtype import is_runtime_subtype
 from mypyc.sametype import is_same_type
@@ -1471,6 +1476,11 @@ def check_tagged_short_int(self, val: Value, line: int, negated: bool = False) -
 
     def compare_strings(self, lhs: Value, rhs: Value, op: str, line: int) -> Value:
         """Compare two strings"""
+        if op == "==":
+            return self.primitive_op(str_eq, [lhs, rhs], line)
+        elif op == "!=":
+            eq = self.primitive_op(str_eq, [lhs, rhs], line)
+            return self.add(ComparisonOp(eq, self.false(), ComparisonOp.EQ, line))
         compare_result = self.call_c(unicode_compare, [lhs, rhs], line)
         error_constant = Integer(-1, c_int_rprimitive, line)
         compare_error_check = self.add(

mypyc/lib-rt/CPy.h

@@ -726,6 +726,7 @@ static inline char CPyDict_CheckSize(PyObject *dict, CPyTagged size) {
 #define RIGHTSTRIP 1
 #define BOTHSTRIP  2
 
+char CPyStr_Equal(PyObject *str1, PyObject *str2);
 PyObject *CPyStr_Build(Py_ssize_t len, ...);
 PyObject *CPyStr_GetItem(PyObject *str, CPyTagged index);
 CPyTagged CPyStr_Find(PyObject *str, PyObject *substr, CPyTagged start, int direction);

mypyc/lib-rt/str_ops.c

@@ -64,6 +64,22 @@ make_bloom_mask(int kind, const void* ptr, Py_ssize_t len)
 #undef BLOOM_UPDATE
 }
 
+// Adapted from CPython 3.13.1 (_PyUnicode_Equal)
+char CPyStr_Equal(PyObject *str1, PyObject *str2) {
+    if (str1 == str2) {
+        return 1;
+    }
+    Py_ssize_t len = PyUnicode_GET_LENGTH(str1);
+    if (PyUnicode_GET_LENGTH(str2) != len)
+        return 0;
+    int kind = PyUnicode_KIND(str1);
+    if (PyUnicode_KIND(str2) != kind)
+        return 0;
+    const void *data1 = PyUnicode_DATA(str1);
+    const void *data2 = PyUnicode_DATA(str2);
+    return memcmp(data1, data2, len * kind) == 0;
+}
+
 PyObject *CPyStr_GetItem(PyObject *str, CPyTagged index) {
     if (PyUnicode_READY(str) != -1) {
         if (CPyTagged_CheckShort(index)) {

mypyc/primitives/str_ops.py

@@ -21,6 +21,7 @@
     ERR_NEG_INT,
     binary_op,
     custom_op,
+    custom_primitive_op,
     function_op,
     load_address_op,
     method_op,
@@ -69,6 +70,15 @@
     steals=[True, False],
 )
 
+# str1 == str2 (very common operation, so we provide our own)
+str_eq = custom_primitive_op(
+    name="str_eq",
+    c_function_name="CPyStr_Equal",
+    arg_types=[str_rprimitive, str_rprimitive],
+    return_type=bool_rprimitive,
+    error_kind=ERR_NEVER,
+)
+
 unicode_compare = custom_op(
     arg_types=[str_rprimitive, str_rprimitive],
     return_type=c_int_rprimitive,

mypyc/test-data/irbuild-dict.test

@@ -399,12 +399,9 @@ def typeddict(d):
     r9, k :: str
     v :: object
     r10 :: str
-    r11 :: i32
-    r12 :: bit
-    r13 :: object
-    r14, r15, r16 :: bit
+    r11 :: bool
     name :: object
-    r17, r18 :: bit
+    r12, r13 :: bit
 L0:
     r0 = 0
     r1 = PyDict_Size(d)
@@ -415,35 +412,25 @@ L1:
     r5 = r4[1]
     r0 = r5
     r6 = r4[0]
-    if r6 goto L2 else goto L9 :: bool
+    if r6 goto L2 else goto L6 :: bool
 L2:
     r7 = r4[2]
     r8 = r4[3]
     r9 = cast(str, r7)
     k = r9
     v = r8
     r10 = 'name'
-    r11 = PyUnicode_Compare(k, r10)
-    r12 = r11 == -1
-    if r12 goto L3 else goto L5 :: bool
+    r11 = CPyStr_Equal(k, r10)
+    if r11 goto L3 else goto L4 :: bool
 L3:
-    r13 = PyErr_Occurred()
-    r14 = r13 != 0
-    if r14 goto L4 else goto L5 :: bool
+    name = v
 L4:
-    r15 = CPy_KeepPropagating()
 L5:
-    r16 = r11 == 0
-    if r16 goto L6 else goto L7 :: bool
+    r12 = CPyDict_CheckSize(d, r2)
+    goto L1
 L6:
-    name = v
+    r13 = CPy_NoErrOccurred()
 L7:
-L8:
-    r17 = CPyDict_CheckSize(d, r2)
-    goto L1
-L9:
-    r18 = CPy_NoErrOccurred()
-L10:
     return 1
 
 [case testDictLoadAddress]

mypyc/test-data/irbuild-str.test

@@ -65,42 +65,18 @@ def neq(x: str, y: str) -> bool:
 [out]
 def eq(x, y):
     x, y :: str
-    r0 :: i32
-    r1 :: bit
-    r2 :: object
-    r3, r4, r5 :: bit
+    r0 :: bool
 L0:
-    r0 = PyUnicode_Compare(x, y)
-    r1 = r0 == -1
-    if r1 goto L1 else goto L3 :: bool
-L1:
-    r2 = PyErr_Occurred()
-    r3 = r2 != 0
-    if r3 goto L2 else goto L3 :: bool
-L2:
-    r4 = CPy_KeepPropagating()
-L3:
-    r5 = r0 == 0
-    return r5
+    r0 = CPyStr_Equal(x, y)
+    return r0
 def neq(x, y):
     x, y :: str
-    r0 :: i32
+    r0 :: bool
     r1 :: bit
-    r2 :: object
-    r3, r4, r5 :: bit
 L0:
-    r0 = PyUnicode_Compare(x, y)
-    r1 = r0 == -1
-    if r1 goto L1 else goto L3 :: bool
-L1:
-    r2 = PyErr_Occurred()
-    r3 = r2 != 0
-    if r3 goto L2 else goto L3 :: bool
-L2:
-    r4 = CPy_KeepPropagating()
-L3:
-    r5 = r0 != 0
-    return r5
+    r0 = CPyStr_Equal(x, y)
+    r1 = r0 == 0
+    return r1
 
 [case testStrReplace]
 from typing import Optional

mypyc/test-data/irbuild-unreachable.test

@@ -11,41 +11,27 @@ def f():
     r1 :: str
     r2 :: object
     r3, r4 :: str
-    r5 :: i32
-    r6 :: bit
-    r7 :: object
-    r8, r9, r10 :: bit
-    r11, r12 :: bool
-    r13 :: object
-    r14, y :: bool
+    r5, r6, r7 :: bool
+    r8 :: object
+    r9, y :: bool
 L0:
     r0 = sys :: module
     r1 = 'platform'
     r2 = CPyObject_GetAttr(r0, r1)
     r3 = cast(str, r2)
     r4 = 'x'
-    r5 = PyUnicode_Compare(r3, r4)
-    r6 = r5 == -1
-    if r6 goto L1 else goto L3 :: bool
+    r5 = CPyStr_Equal(r3, r4)
+    if r5 goto L2 else goto L1 :: bool
 L1:
-    r7 = PyErr_Occurred()
-    r8 = r7 != 0
-    if r8 goto L2 else goto L3 :: bool
+    r6 = r5
+    goto L3
 L2:
-    r9 = CPy_KeepPropagating()
+    r7 = raise RuntimeError('mypyc internal error: should be unreachable')
+    r8 = box(None, 1)
+    r9 = unbox(bool, r8)
+    r6 = r9
 L3:
-    r10 = r5 == 0
-    if r10 goto L5 else goto L4 :: bool
-L4:
-    r11 = r10
-    goto L6
-L5:
-    r12 = raise RuntimeError('mypyc internal error: should be unreachable')
-    r13 = box(None, 1)
-    r14 = unbox(bool, r13)
-    r11 = r14
-L6:
-    y = r11
+    y = r6
     return 1
 
 [case testUnreachableNameExpr]
@@ -59,41 +45,27 @@ def f():
     r1 :: str
     r2 :: object
     r3, r4 :: str
-    r5 :: i32
-    r6 :: bit
-    r7 :: object
-    r8, r9, r10 :: bit
-    r11, r12 :: bool
-    r13 :: object
-    r14, y :: bool
+    r5, r6, r7 :: bool
+    r8 :: object
+    r9, y :: bool
 L0:
     r0 = sys :: module
     r1 = 'platform'
     r2 = CPyObject_GetAttr(r0, r1)
     r3 = cast(str, r2)
     r4 = 'x'
-    r5 = PyUnicode_Compare(r3, r4)
-    r6 = r5 == -1
-    if r6 goto L1 else goto L3 :: bool
+    r5 = CPyStr_Equal(r3, r4)
+    if r5 goto L2 else goto L1 :: bool
 L1:
-    r7 = PyErr_Occurred()
-    r8 = r7 != 0
-    if r8 goto L2 else goto L3 :: bool
+    r6 = r5
+    goto L3
 L2:
-    r9 = CPy_KeepPropagating()
+    r7 = raise RuntimeError('mypyc internal error: should be unreachable')
+    r8 = box(None, 1)
+    r9 = unbox(bool, r8)
+    r6 = r9
 L3:
-    r10 = r5 == 0
-    if r10 goto L5 else goto L4 :: bool
-L4:
-    r11 = r10
-    goto L6
-L5:
-    r12 = raise RuntimeError('mypyc internal error: should be unreachable')
-    r13 = box(None, 1)
-    r14 = unbox(bool, r13)
-    r11 = r14
-L6:
-    y = r11
+    y = r6
     return 1
 
 [case testUnreachableStatementAfterReturn]