[mypyc] Try to fix mypy mac build failure on Python 3.5 on Travis (#9508)

We may be building a mixed 32/64-bit binary, so restrict the maximum integer
literal to what's supported on a 32-bit platform, since the same C code
needs to compile on both 32-bit and 64-bit architectures.

This will make some slicing operations a bit slower in 32/64-bit mode
(Python 3.5 on mac).

Work on #9500.

Author: JukkaL

mypyc/common.py

@@ -24,11 +24,6 @@
 # Max short int we accept as a literal is based on 32-bit platforms,
 # so that we can just always emit the same code.
 
-# Maximum value for a short tagged integer.
-#
-# Note: Assume that the compiled code uses the same bit width as mypyc.
-MAX_LITERAL_SHORT_INT = sys.maxsize >> 1  # type: Final
-
 TOP_LEVEL_NAME = '__top_level__'  # type: Final # Special function representing module top level
 
 # Maximal number of subclasses for a class to trigger fast path in isinstance() checks.
@@ -38,6 +33,23 @@
 
 PLATFORM_SIZE = 4 if IS_32_BIT_PLATFORM else 8
 
+# Python 3.5 on macOS uses a hybrid 32/64-bit build that requires some workarounds.
+# The same generated C will be compiled in both 32 and 64 bit modes when building mypy
+# wheels (for an unknown reason).
+#
+# Note that we use "in ['darwin']" because of https://github.com/mypyc/mypyc/issues/761.
+IS_MIXED_32_64_BIT_BUILD = sys.platform in ['darwin'] and sys.version_info < (3, 6)  # type: Final
+
+# Maximum value for a short tagged integer.
+MAX_SHORT_INT = sys.maxsize >> 1  # type: Final
+
+# Maximum value for a short tagged integer represented as a C integer literal.
+#
+# Note: Assume that the compiled code uses the same bit width as mypyc, except for
+#       Python 3.5 on macOS.
+MAX_LITERAL_SHORT_INT = (sys.maxsize >> 1 if not IS_MIXED_32_64_BIT_BUILD
+                         else 2**30 - 1)  # type: Final
+
 # Runtime C library files
 RUNTIME_C_FILES = [
     'init.c',

mypyc/irbuild/expression.py

@@ -15,7 +15,7 @@
 )
 from mypy.types import TupleType, get_proper_type, Instance
 
-from mypyc.common import MAX_LITERAL_SHORT_INT
+from mypyc.common import MAX_SHORT_INT
 from mypyc.ir.ops import (
     Value, TupleGet, TupleSet, BasicBlock, Assign, LoadAddress
 )
@@ -373,7 +373,7 @@ def try_gen_slice_op(builder: IRBuilder, base: Value, index: SliceExpr) -> Optio
         else:
             # Replace missing end index with the largest short integer
             # (a sequence can't be longer).
-            end = builder.load_static_int(MAX_LITERAL_SHORT_INT)
+            end = builder.load_static_int(MAX_SHORT_INT)
         candidates = [list_slice_op, tuple_slice_op, str_slice_op]
         return builder.builder.matching_call_c(candidates, [base, begin, end], index.line)