Clarify rules for names of HloInstructions and HloOpcodes.

- The name of an HloInstruction may not contain "::", as this is used as a
  separator in fully qualified names.
- The name of an HloOpcode may not contain ':', as this is used as a separator
  in extended opcode strings.

PiperOrigin-RevId: 160894413

1 files changed, 7 insertions, 0 deletions

diff --git a/tensorflow/compiler/xla/service/hlo_opcode.cc b/tensorflow/compiler/xla/service/hlo_opcode.cc
index 4d68d0d088..53a93f3dac 100644
--- a/tensorflow/compiler/xla/service/hlo_opcode.cc
+++ b/tensorflow/compiler/xla/service/hlo_opcode.cc
@@ -19,6 +19,13 @@ limitations under the License.
 namespace xla {
 
 string HloOpcodeString(HloOpcode opcode) {
+  // Note: Do not use ':' in opcode strings. It is used as a special character
+  // in these places:
+  // - In extended opcode strings (HloInstruction::ExtendedOpcodeString()), to
+  //   separate the opcode from the fusion kind
+  // - In fully qualified names (HloInstruction::FullyQualifiedName()), to
+  //   separate the qualifiers (name of the computation and potentially the
+  //   fusion instruction) from the name
   switch (opcode) {
     case HloOpcode::kAbs:
       return "abs";