[StableHashing] Hash machine basic blocks and functions

This adds very basic support for hashing MachineBasicBlock
and MachineFunction, for use in MachineFunctionPass to
detect passes that modify the MachineFunction wrongly.

Differential Revision: https://reviews.llvm.org/D120122

llvm/include/llvm/CodeGen/MachineStableHash.h

@@ -17,6 +17,8 @@
 #include "llvm/CodeGen/StableHashing.h"
 
 namespace llvm {
+class MachineBasicBlock;
+class MachineFunction;
 class MachineInstr;
 class MachineOperand;
 
@@ -24,6 +26,8 @@ stable_hash stableHashValue(const MachineOperand &MO);
 stable_hash stableHashValue(const MachineInstr &MI, bool HashVRegs = false,
                             bool HashConstantPoolIndices = false,
                             bool HashMemOperands = false);
+stable_hash stableHashValue(const MachineBasicBlock &MBB);
+stable_hash stableHashValue(const MachineFunction &MF);
 
 } // namespace llvm
 

llvm/lib/CodeGen/MachineStableHash.cpp

@@ -195,3 +195,21 @@ stable_hash llvm::stableHashValue(const MachineInstr &MI, bool HashVRegs,
   return stable_hash_combine_range(HashComponents.begin(),
                                    HashComponents.end());
 }
+
+stable_hash llvm::stableHashValue(const MachineBasicBlock &MBB) {
+  SmallVector<stable_hash> HashComponents;
+  // TODO: Hash more stuff like block alignment and branch probabilities.
+  for (auto &MI : MBB)
+    HashComponents.push_back(stableHashValue(MI));
+  return stable_hash_combine_range(HashComponents.begin(),
+                                   HashComponents.end());
+}
+
+stable_hash llvm::stableHashValue(const MachineFunction &MF) {
+  SmallVector<stable_hash> HashComponents;
+  // TODO: Hash lots more stuff like function alignment and stack objects.
+  for (auto &MBB : MF)
+    HashComponents.push_back(stableHashValue(MBB));
+  return stable_hash_combine_range(HashComponents.begin(),
+                                   HashComponents.end());
+}