[MIRVRegNamer] Experimental MachineInstr stable hashing (Fowler-Noll-Vo)

This hashing scheme has been useful out of tree, and I want to start
experimenting with it. Specifically I want to experiment on the
MIRVRegNamer, MIRCanononicalizer, and eventually the MachineOutliner.

This diff is a first step, that optionally brings stable hashing to the
MIRVRegNamer (and as a result, the MIRCanonicalizer).  We've tested this
hashing scheme on a lot of MachineOperand types that llvm::hash_value
can not handle in a stable manner.

This stable hashing was also the basis for

"Global Machine Outliner for ThinLTO" in EuroLLVM 2020

http://llvm.org/devmtg/2020-04/talks.html#TechTalk_58

Credits: Kyungwoo Lee, Nikolai Tillmann

Differential Revision: https://reviews.llvm.org/D86952

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineOperand.cpp b/llvm/lib/CodeGen/MachineOperand.cpp
index cece914..ce33cdb 100644
--- a/llvm/lib/CodeGen/MachineOperand.cpp
+++ b/llvm/lib/CodeGen/MachineOperand.cpp
@@ -415,6 +415,11 @@ static const char *getTargetIndexName(const MachineFunction &MF, int Index) {
   return nullptr;
 }
 
+const char *MachineOperand::getTargetIndexName() const {
+  const MachineFunction *MF = getMFIfAvailable(*this);
+  return MF ? ::getTargetIndexName(*MF, this->getIndex()) : nullptr;
+}
+
 static const char *getTargetFlagName(const TargetInstrInfo *TII, unsigned TF) {
   auto Flags = TII->getSerializableDirectMachineOperandTargetFlags();
   for (const auto &I : Flags) {
@@ -823,7 +828,7 @@ void MachineOperand::print(raw_ostream &OS, ModuleSlotTracker &MST,
     OS << "target-index(";
     const char *Name = "<unknown>";
     if (const MachineFunction *MF = getMFIfAvailable(*this))
-      if (const auto *TargetIndexName = getTargetIndexName(*MF, getIndex()))
+      if (const auto *TargetIndexName = ::getTargetIndexName(*MF, getIndex()))
         Name = TargetIndexName;
     OS << Name << ')';
     printOperandOffset(OS, getOffset());