compiler: Catch escaping numpy.{array, full, transpose}() results

Function calls in general can still be used to hide escaping
allocations from the compiler (issue #1497), but these calls in
particular always allocate, so we can easily and accurately handle
them.

artiq/compiler/validators/escape.py

@@ -102,7 +102,19 @@ class RegionOf(algorithm.Visitor):
         if types.is_external_function(node.func.type, "cache_get"):
             # The cache is borrow checked dynamically
             return Global()
-        else:
+
+        if (types.is_builtin_function(node.func.type, "array")
+              or types.is_builtin_function(node.func.type, "make_array")
+              or types.is_builtin_function(node.func.type, "numpy.transpose")):
+            # While lifetime tracking across function calls in general is currently
+            # broken (see below), these special builtins that allocate an array on
+            # the stack of the caller _always_ allocate regardless of the parameters,
+            # and we can thus handle them without running into the precision issue
+            # mentioned in commit ae999db.
+            return self.visit_allocating(node)
+
+        # FIXME: Return statement missing here, but see m-labs/artiq#1497 and
+        # commit ae999db.
         self.visit_sometimes_allocating(node)
 
     # Value lives as long as the object/container, if it's mutable,

artiq/test/lit/escape/error_numpy_array.py

@@ -0,0 +1,15 @@
+# RUN: %python -m artiq.compiler.testbench.embedding +diag %s 2>%t
+# RUN: OutputCheck %s --file-to-check=%t
+
+from artiq.experiment import *
+import numpy as np
+
+@kernel
+def a():
+    # CHECK-L: ${LINE:+2}: error: cannot return an allocated value that does not live forever
+    # CHECK-L: ${LINE:+1}: note: ... to this point
+    return np.array([0, 1])
+
+@kernel
+def entrypoint():
+    a()

artiq/test/lit/escape/error_numpy_full.py

@@ -0,0 +1,16 @@
+# RUN: %python -m artiq.compiler.testbench.embedding +diag %s 2>%t
+# RUN: OutputCheck %s --file-to-check=%t
+
+from artiq.experiment import *
+import numpy as np
+
+@kernel
+def a():
+    # CHECK-L: ${LINE:+2}: error: cannot return an allocated value that does not live forever
+    # CHECK-L: ${LINE:+1}: note: ... to this point
+    return np.full(10, 42.0)
+
+
+@kernel
+def entrypoint():
+    a()

artiq/test/lit/escape/error_numpy_transpose.py

@@ -0,0 +1,17 @@
+# RUN: %python -m artiq.compiler.testbench.embedding +diag %s 2>%t
+# RUN: OutputCheck %s --file-to-check=%t
+
+from artiq.experiment import *
+import numpy as np
+
+data = np.array([[0, 1], [2, 3]])
+
+@kernel
+def a():
+    # CHECK-L: ${LINE:+2}: error: cannot return an allocated value that does not live forever
+    # CHECK-L: ${LINE:+1}: note: ... to this point
+    return np.transpose(data)
+
+@kernel
+def entrypoint():
+    a()

doc/manual/compiler.rst

@@ -95,24 +95,6 @@ tracked across function calls (see `#1497 <https://github.com/m-labs/artiq/issue
         def run(self):
             # results in memory corruption
             return func([1, 2, 3])
-or if the return value is obfuscated by an if-statement like here: ::
-
-    class ProblemReturn2(EnvExperiment):
-        def build(self):
-            self.setattr_device("core")
-
-        @kernel
-        def meth(self):
-            # if statement for obfuscation
-            if self.core.get_rtio_counter_mu() % 2:
-                return np.array([1,2,3])
-            else:
-                return np.array([4,5,6])
-
-        @kernel
-        def run(self):
-            # also results in memory corrption
-            return self.meth()
 
 This results in memory corruption at runtime.