From f8c2709943587caf90d9d023b47a9e948646ed15 Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Thu, 23 Jul 2015 01:26:50 +0300
Subject: [PATCH] Make division by zero raise an exception.

---
 artiq/compiler/builtins.py                    |  7 ++++++
 artiq/compiler/prelude.py                     | 25 ++++++++++---------
 .../compiler/transforms/artiq_ir_generator.py |  5 +++-
 3 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/artiq/compiler/builtins.py b/artiq/compiler/builtins.py
index dde80af12..73035600d 100644
--- a/artiq/compiler/builtins.py
+++ b/artiq/compiler/builtins.py
@@ -83,6 +83,10 @@ class TValueError(TException):
     def __init__(self):
         super().__init__("ValueError")
 
+class TZeroDivisionError(TException):
+    def __init__(self):
+        super().__init__("ZeroDivisionError")
+
 def fn_bool():
     return types.TConstructor("bool")
 
@@ -107,6 +111,9 @@ def fn_IndexError():
 def fn_ValueError():
     return types.TExceptionConstructor("ValueError")
 
+def fn_ZeroDivisionError():
+    return types.TExceptionConstructor("ZeroDivisionError")
+
 def fn_range():
     return types.TBuiltinFunction("range")
 
diff --git a/artiq/compiler/prelude.py b/artiq/compiler/prelude.py
index bed44af6c..600b7a800 100644
--- a/artiq/compiler/prelude.py
+++ b/artiq/compiler/prelude.py
@@ -7,16 +7,17 @@ from . import builtins
 
 def globals():
     return {
-        "bool":         builtins.fn_bool(),
-        "int":          builtins.fn_int(),
-        "float":        builtins.fn_float(),
-        "list":         builtins.fn_list(),
-        "range":        builtins.fn_range(),
-        "Exception":    builtins.fn_Exception(),
-        "IndexError":   builtins.fn_IndexError(),
-        "ValueError":   builtins.fn_ValueError(),
-        "len":          builtins.fn_len(),
-        "round":        builtins.fn_round(),
-        "print":        builtins.fn_print(),
-        "syscall":      builtins.fn_syscall(),
+        "bool":                 builtins.fn_bool(),
+        "int":                  builtins.fn_int(),
+        "float":                builtins.fn_float(),
+        "list":                 builtins.fn_list(),
+        "range":                builtins.fn_range(),
+        "Exception":            builtins.fn_Exception(),
+        "IndexError":           builtins.fn_IndexError(),
+        "ValueError":           builtins.fn_ValueError(),
+        "ZeroDivisionError":    builtins.fn_ZeroDivisionError(),
+        "len":                  builtins.fn_len(),
+        "round":                builtins.fn_round(),
+        "print":                builtins.fn_print(),
+        "syscall":              builtins.fn_syscall(),
     }
diff --git a/artiq/compiler/transforms/artiq_ir_generator.py b/artiq/compiler/transforms/artiq_ir_generator.py
index 502ad651a..1c49508e2 100644
--- a/artiq/compiler/transforms/artiq_ir_generator.py
+++ b/artiq/compiler/transforms/artiq_ir_generator.py
@@ -899,13 +899,16 @@ class ARTIQIRGenerator(algorithm.Visitor):
 
     def visit_BinOpT(self, node):
         if builtins.is_numeric(node.type):
-            # TODO: check for division by zero
             rhs = self.visit(node.right)
             if isinstance(node.op, (ast.LShift, ast.RShift)):
                 # Check for negative shift amount.
                 self._make_check(self.append(ir.Compare(ast.GtE(loc=None), rhs,
                                                         ir.Constant(0, rhs.type))),
                                  lambda: self.append(ir.Alloc([], builtins.TValueError())))
+            elif isinstance(node.op, (ast.Div, ast.FloorDiv)):
+                self._make_check(self.append(ir.Compare(ast.NotEq(loc=None), rhs,
+                                                        ir.Constant(0, rhs.type))),
+                                 lambda: self.append(ir.Alloc([], builtins.TZeroDivisionError())))
 
             return self.append(ir.Arith(node.op, self.visit(node.left), rhs))
         elif isinstance(node.op, ast.Add): # list + list, tuple + tuple