Try to clarify this comment some.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152221 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index 3dbfda6..4a68067 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -1850,10 +1850,13 @@
// MachineOperand, but currently that doesn't work because there are many
// different ideas of "equality" and thus different sets of information that
// contribute to the hash code. This one happens to want to take a specific
- // subset. It's not clear that this routine uses the correct set of
- // information, it would be good to somehow ensure this function is
- // MachineInstr::isIdenticalTo with the 'IgnoreVRegDefs' filter look at the
- // same bits.
+ // subset. And it's still not clear that this routine uses the *correct*
+ // subset of information when computing the hash code. The goal is to use the
+ // same inputs for the hash code here that MachineInstr::isIdenticalTo uses to
+ // test for equality when passed the 'IgnoreVRegDefs' filter flag. It would
+ // be very useful to factor the selection of relevant inputs out of the two
+ // functions and into a common routine, but it's not clear how that can be
+ // done.
SmallVector<size_t, 8> HashComponents;
HashComponents.reserve(MI->getNumOperands() + 1);
HashComponents.push_back(MI->getOpcode());