From e4ffd81852d297b77847cc4fae05e1ba741769e7 Mon Sep 17 00:00:00 2001
From: Andreas Kloeckner <inform@tiker.net>
Date: Mon, 19 Aug 2019 20:17:23 -0500
Subject: [PATCH] Add C Integer semantics experiment
---
contrib/c-integer-semantics.py | 145 +++++++++++++++++++++++++++++++++
1 file changed, 145 insertions(+)
create mode 100644 contrib/c-integer-semantics.py
diff --git a/contrib/c-integer-semantics.py b/contrib/c-integer-semantics.py
new file mode 100644
index 000000000..ffdeecc85
--- /dev/null
+++ b/contrib/c-integer-semantics.py
@@ -0,0 +1,145 @@
+#!/usr/bin/env python
+# coding: utf-8
+
+from os import system
+import ctypes
+
+C_SRC = """
+#include <stdlib.h>
+#include <stdint.h>
+
+int64_t cdiv(int64_t a, int64_t b)
+{
+ return a/b;
+}
+
+int64_t cmod(int64_t a, int64_t b)
+{
+ return a%b;
+}
+
+#define LOOPY_CALL_WITH_INTEGER_TYPES(MACRO_NAME) \
+ MACRO_NAME(short) \
+ MACRO_NAME(int) \
+ MACRO_NAME(long) \
+ MACRO_NAME(int64_t)
+
+#define LOOPY_DEFINE_FLOOR_DIV(TYPE) \
+ TYPE loopy_floor_div_##TYPE(TYPE a, TYPE b) \
+ { \
+ if ((a<0) != (b<0)) \
+ a = a - (b + (b<0) - (b>=0)); \
+ return a/b; \
+ }
+
+LOOPY_CALL_WITH_INTEGER_TYPES(LOOPY_DEFINE_FLOOR_DIV)
+#undef LOOPY_DEFINE_FLOOR_DIV
+
+#define LOOPY_DEFINE_FLOOR_DIV_POS_B(TYPE) \
+ TYPE loopy_floor_div_pos_b_##TYPE(TYPE a, TYPE b) \
+ { \
+ if (a<0) \
+ a = a - (b-1); \
+ return a/b; \
+ }
+
+LOOPY_CALL_WITH_INTEGER_TYPES(LOOPY_DEFINE_FLOOR_DIV_POS_B)
+#undef LOOPY_DEFINE_FLOOR_DIV_POS_B
+
+
+#define LOOPY_DEFINE_MOD_POS_B(TYPE) \
+ TYPE loopy_mod_pos_b_##TYPE(TYPE a, TYPE b) \
+ { \
+ TYPE result = a%b; \
+ if (result < 0) \
+ result += b; \
+ return result; \
+ }
+
+LOOPY_CALL_WITH_INTEGER_TYPES(LOOPY_DEFINE_MOD_POS_B)
+#undef LOOPY_DEFINE_MOD_POS_B
+
+#define LOOPY_DEFINE_MOD(TYPE) \
+ TYPE loopy_mod_##TYPE(TYPE a, TYPE b) \
+ { \
+ TYPE result = a%b; \
+ if (result < 0 && b > 0) \
+ result += b; \
+ if (result > 0 && b < 0) \
+ result = result + b; \
+ return result; \
+ }
+
+LOOPY_CALL_WITH_INTEGER_TYPES(LOOPY_DEFINE_MOD)
+#undef LOOPY_DEFINE_MOD
+
+
+"""
+
+
+def main():
+ with open("int-experiments.c", "w") as outf:
+ outf.write(C_SRC)
+
+ system('gcc -Wall -shared int-experiments.c -o int-experiments.so')
+
+ int_exp = ctypes.CDLL("int-experiments.so")
+ for func in [
+ int_exp.cdiv,
+ int_exp.cmod,
+ int_exp.loopy_floor_div_int64_t,
+ int_exp.loopy_floor_div_pos_b_int64_t,
+ int_exp.loopy_mod_pos_b_int64_t,
+ int_exp.loopy_mod_int64_t,
+ ]:
+ func.argtypes = [ctypes.c_longlong, ctypes.c_longlong]
+ func.restype = ctypes.c_longlong
+
+ cdiv = int_exp.cdiv # noqa
+ cmod = int_exp.cmod # noqa
+ int_floor_div = int_exp.loopy_floor_div_int64_t
+ int_floor_div_pos_b = int_exp.loopy_floor_div_pos_b_int64_t
+ int_mod_pos_b = int_exp.loopy_mod_pos_b_int64_t
+ int_mod = int_exp.loopy_mod_int64_t
+
+ m = 50
+
+ for a in range(-m, m):
+ for b in range(1, m):
+ cresult = int_floor_div_pos_b(a, b)
+ presult = a // b
+ assert cresult == presult
+ if cresult != presult:
+ print(a, b, cresult, presult)
+
+ for a in range(-m, m):
+ for b in range(-m, m):
+ if b == 0:
+ continue
+
+ cresult = int_floor_div(a, b)
+ presult = a // b
+ assert cresult == presult
+ if cresult != presult:
+ print(a, b, cresult, presult)
+
+ for a in range(-m, m):
+ for b in range(1, m):
+ cresult = int_mod_pos_b(a, b)
+ presult = a % b
+ assert cresult == presult
+
+ for a in range(-m, m):
+ for b in range(-m, m):
+ if b == 0:
+ continue
+
+ cresult = int_mod(a, b)
+ presult = a % b
+ assert cresult == presult
+ if cresult != presult:
+ print(a, b, cresult, presult)
+
+
+if __name__ == "__main__":
+ main()
--
GitLab