compiler: coerce `while` condition to bool.

Fixes #768.

artiq/compiler/transforms/artiq_ir_generator.py

@@ -451,6 +451,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
             self.current_block = head
             old_continue, self.continue_target = self.continue_target, head
             cond = self.visit(node.test)
+            cond = self.coerce_to_bool(cond)
             post_head = self.current_block
 
             break_block = self.add_block("while.break")

artiq/test/lit/integration/if.py

@@ -19,3 +19,9 @@ else:
 
 assert (0 if True else 1) == 0
 assert (0 if False else 1) == 1
+
+if 0:
+    assert True
+
+if 1:
+    assert True

artiq/test/lit/integration/while.py

@@ -53,3 +53,10 @@ while True:
     assert False
 else:
     assert False
+
+while 0:
+    assert False
+
+while 1:
+    assert True
+    break