[globalisel][legalizerinfo] Follow up on post-commit review comments after r323681

* Document most API's
* Delete a useless function call
* Fix a discrepancy between the single and multi-opcode variants of
  getActionDefinitions().
  The multi-opcode variant now requires that more than one opcode is requested.
  Previously it acted much like the single-opcode form but unnecessarily
  enforced the requirements of the multi-opcode form.

llvm-svn: 325067

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
index 3b8eb103297..6b2c3644749 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
@@ -261,6 +261,10 @@ LegalizeRuleSet &LegalizerInfo::getActionDefinitionsBuilder(
     std::initializer_list<unsigned> Opcodes) {
   unsigned Representative = *Opcodes.begin();
 
+  assert(Opcodes.begin() != Opcodes.end() &&
+         Opcodes.begin() + 1 != Opcodes.end() &&
+         "Initializer list must have at least two opcodes");
+
   for (auto I = Opcodes.begin() + 1, E = Opcodes.end(); I != E; ++I)
     aliasActionDefinitions(Representative, *I);