[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, 193 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/MachineStableHash.cpp b/llvm/lib/CodeGen/MachineStableHash.cpp
new file mode 100644
index 0000000..7106d41
--- /dev/null
+++ b/llvm/lib/CodeGen/MachineStableHash.cpp
@@ -0,0 +1,193 @@
+//===- lib/CodeGen/MachineStableHash.cpp ----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Stable hashing for MachineInstr and MachineOperand. Useful or getting a
+// hash across runs, modules, etc.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MachineStableHash.h"
+#include "llvm/ADT/FoldingSet.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/Analysis/Loads.h"
+#include "llvm/Analysis/MemoryLocation.h"
+#include "llvm/CodeGen/MIRFormatter.h"
+#include "llvm/CodeGen/MIRPrinter.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineJumpTableInfo.h"
+#include "llvm/CodeGen/MachineOperand.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/StableHashing.h"
+#include "llvm/CodeGen/TargetInstrInfo.h"
+#include "llvm/CodeGen/TargetRegisterInfo.h"
+#include "llvm/Config/llvm-config.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRPrintingPasses.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/ModuleSlotTracker.h"
+#include "llvm/MC/MCDwarf.h"
+#include "llvm/Target/TargetIntrinsicInfo.h"
+#include "llvm/Target/TargetMachine.h"
+
+#define DEBUG_TYPE "machine-stable-hash"
+
+using namespace llvm;
+
+STATISTIC(StableHashBailingMachineBasicBlock,
+          "Number of encountered unsupported MachineOperands that were "
+          "MachineBasicBlocks while computing stable hashes");
+STATISTIC(StableHashBailingConstantPoolIndex,
+          "Number of encountered unsupported MachineOperands that were "
+          "ConstantPoolIndex while computing stable hashes");
+STATISTIC(StableHashBailingTargetIndexNoName,
+          "Number of encountered unsupported MachineOperands that were "
+          "TargetIndex with no name");
+STATISTIC(StableHashBailingGlobalAddress,
+          "Number of encountered unsupported MachineOperands that were "
+          "GlobalAddress while computing stable hashes");
+STATISTIC(StableHashBailingBlockAddress,
+          "Number of encountered unsupported MachineOperands that were "
+          "BlockAddress while computing stable hashes");
+STATISTIC(StableHashBailingMetadataUnsupported,
+          "Number of encountered unsupported MachineOperands that were "
+          "Metadata of an unsupported kind while computing stable hashes");
+
+stable_hash llvm::stableHashValue(const MachineOperand &MO) {
+  switch (MO.getType()) {
+  case MachineOperand::MO_Register:
+    if (Register::isVirtualRegister(MO.getReg())) {
+      const MachineRegisterInfo &MRI = MO.getParent()->getMF()->getRegInfo();
+      return MRI.getVRegDef(MO.getReg())->getOpcode();
+    }
+
+    // Register operands don't have target flags.
+    return stable_hash_combine(MO.getType(), MO.getReg(), MO.getSubReg(),
+                               MO.isDef());
+  case MachineOperand::MO_Immediate:
+    return stable_hash_combine(MO.getType(), MO.getTargetFlags(), MO.getImm());
+  case MachineOperand::MO_CImmediate:
+  case MachineOperand::MO_FPImmediate: {
+    auto Val = MO.isCImm() ? MO.getCImm()->getValue()
+                           : MO.getFPImm()->getValueAPF().bitcastToAPInt();
+    auto ValHash =
+        stable_hash_combine_array(Val.getRawData(), Val.getNumWords());
+    return hash_combine(MO.getType(), MO.getTargetFlags(), ValHash);
+  }
+
+  case MachineOperand::MO_MachineBasicBlock:
+    StableHashBailingMachineBasicBlock++;
+    return 0;
+  case MachineOperand::MO_ConstantPoolIndex:
+    StableHashBailingConstantPoolIndex++;
+    return 0;
+  case MachineOperand::MO_BlockAddress:
+    StableHashBailingBlockAddress++;
+    return 0;
+  case MachineOperand::MO_Metadata:
+    StableHashBailingMetadataUnsupported++;
+    return 0;
+  case MachineOperand::MO_GlobalAddress:
+    StableHashBailingGlobalAddress++;
+    return 0;
+  case MachineOperand::MO_TargetIndex: {
+    if (const char *Name = MO.getTargetIndexName())
+      return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
+                                 stable_hash_combine_string(Name),
+                                 MO.getOffset());
+    StableHashBailingTargetIndexNoName++;
+    return 0;
+  }
+
+  case MachineOperand::MO_FrameIndex:
+  case MachineOperand::MO_JumpTableIndex:
+    return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
+                               MO.getIndex());
+
+  case MachineOperand::MO_ExternalSymbol:
+    return hash_combine(MO.getType(), MO.getTargetFlags(), MO.getOffset(),
+                        stable_hash_combine_string(MO.getSymbolName()));
+
+  case MachineOperand::MO_RegisterMask:
+  case MachineOperand::MO_RegisterLiveOut:
+    return hash_combine(MO.getType(), MO.getTargetFlags(), MO.getRegMask());
+
+  case MachineOperand::MO_ShuffleMask: {
+    std::vector<llvm::stable_hash> ShuffleMaskHashes;
+
+    llvm::transform(
+        MO.getShuffleMask(), std::back_inserter(ShuffleMaskHashes),
+        [](int S) -> llvm::stable_hash { return llvm::stable_hash(S); });
+
+    return hash_combine(MO.getType(), MO.getTargetFlags(),
+                        stable_hash_combine_array(ShuffleMaskHashes.data(),
+                                                  ShuffleMaskHashes.size()));
+  }
+  case MachineOperand::MO_MCSymbol: {
+    auto SymbolName = MO.getMCSymbol()->getName();
+    return hash_combine(MO.getType(), MO.getTargetFlags(),
+                        stable_hash_combine_string(SymbolName));
+  }
+  case MachineOperand::MO_CFIIndex:
+    return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
+                               MO.getCFIIndex());
+  case MachineOperand::MO_IntrinsicID:
+    return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
+                               MO.getIntrinsicID());
+  case MachineOperand::MO_Predicate:
+    return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
+                               MO.getPredicate());
+  }
+  llvm_unreachable("Invalid machine operand type");
+}
+
+/// A stable hash value for machine instructions.
+/// Returns 0 if no stable hash could be computed.
+/// The hashing and equality testing functions ignore definitions so this is
+/// useful for CSE, etc.
+stable_hash llvm::stableHashValue(const MachineInstr &MI, bool HashVRegs,
+                                  bool HashConstantPoolIndices,
+                                  bool HashMemOperands) {
+  // Build up a buffer of hash code components.
+  SmallVector<stable_hash, 16> HashComponents;
+  HashComponents.reserve(MI.getNumOperands() + MI.getNumMemOperands() + 2);
+  HashComponents.push_back(MI.getOpcode());
+  HashComponents.push_back(MI.getFlags());
+  for (const MachineOperand &MO : MI.operands()) {
+    if (!HashVRegs && MO.isReg() && MO.isDef() &&
+        Register::isVirtualRegister(MO.getReg()))
+      continue; // Skip virtual register defs.
+
+    if (MO.isCPI()) {
+      HashComponents.push_back(stable_hash_combine(
+          MO.getType(), MO.getTargetFlags(), MO.getIndex()));
+      continue;
+    }
+
+    stable_hash StableHash = stableHashValue(MO);
+    if (!StableHash)
+      return 0;
+    HashComponents.push_back(StableHash);
+  }
+
+  for (const auto *Op : MI.memoperands()) {
+    if (!HashMemOperands)
+      break;
+    HashComponents.push_back(static_cast<unsigned>(Op->getSize()));
+    HashComponents.push_back(static_cast<unsigned>(Op->getFlags()));
+    HashComponents.push_back(static_cast<unsigned>(Op->getOffset()));
+    HashComponents.push_back(static_cast<unsigned>(Op->getOrdering()));
+    HashComponents.push_back(static_cast<unsigned>(Op->getAddrSpace()));
+    HashComponents.push_back(static_cast<unsigned>(Op->getSyncScopeID()));
+    HashComponents.push_back(static_cast<unsigned>(Op->getBaseAlign().value()));
+    HashComponents.push_back(static_cast<unsigned>(Op->getFailureOrdering()));
+  }
+
+  return stable_hash_combine_range(HashComponents.begin(),
+                                   HashComponents.end());
+}