Subzero: Update tests and build scripts for sandboxing.

runtime/szrt.c

Index: runtime/szrt.c
diff --git a/runtime/szrt.c b/runtime/szrt.c
index 472175860b7bb1ea8c33f6c8973b7150038252b4..8e094bc58a19c556860aa047053a208bd6b5a74f 100644
--- a/runtime/szrt.c
+++ b/runtime/szrt.c
@@ -7,17 +7,37 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This file implements the runtime helper routines that are needed by
-// Subzero.  This needs to be compiled by some non-Subzero compiler.
+// This file implements wrappers for particular bitcode instructions
+// that are too uncommon and complex for a particular target to bother
+// implementing directly in Subzero target lowering.  This needs to be
+// compiled by some non-Subzero compiler.
 //
 //===----------------------------------------------------------------------===//
 
 #include <stdint.h>
 #include <stdlib.h>
 
-uint32_t cvtftoui32(float value) { return (uint32_t)value; }
+// TODO(stichnot): The various NaN cross tests try to map Subzero's
+// undefined behavior to the same as llc's undefined behavior, as
+// observed by the cross tests.  This will have to be kept up to date
+// with any future changes to llc, and may also have to be different
+// for different targets.  It would be better to find a more
+// appropriate set of llc options when building the Subzero runtime.
+//
+// We test for NaN using "value==value" instead of using isnan(value)
+// to avoid an external dependency on fpclassify().
+
+uint32_t cvtftoui32(float value) {
+  if (value == value) // NaNaN
+    return (uint32_t)value;
+  return 0x80000000;
+}
 
-uint32_t cvtdtoui32(double value) { return (uint32_t)value; }
+uint32_t cvtdtoui32(double value) {
+  if (value == value) // NaNaN
+    return (uint32_t)value;
+  return 0x80000000;
+}
 
 int64_t cvtftosi64(float value) { return (int64_t)value; }