[llvm-branch-commits] [llvm] [StructuralHash] Support Differences (PR #112638)

[Ellis Hoag via llvm-branch-commits]

================
@@ -47,24 +60,140 @@ class StructuralHashImpl {
 
 public:
   StructuralHashImpl() = delete;
-  explicit StructuralHashImpl(bool DetailedHash) : DetailedHash(DetailedHash) {}
+  explicit StructuralHashImpl(bool DetailedHash,
+                              IgnoreOperandFunc IgnoreOp = nullptr)
+      : DetailedHash(DetailedHash), IgnoreOp(IgnoreOp) {
+    if (IgnoreOp) {
+      IndexInstruction = std::make_unique<IndexInstrMap>();
+      IndexOperandHashMap = std::make_unique<IndexOperandHashMapType>();
+    }
+  }
 
-  stable_hash hashConstant(Constant *C) {
+  stable_hash hashAPInt(const APInt &I) {
     SmallVector<stable_hash> Hashes;
-    // TODO: hashArbitaryType() is not stable.
-    if (ConstantInt *ConstInt = dyn_cast<ConstantInt>(C)) {
-      Hashes.emplace_back(hashArbitaryType(ConstInt->getValue()));
-    } else if (ConstantFP *ConstFP = dyn_cast<ConstantFP>(C)) {
-      Hashes.emplace_back(hashArbitaryType(ConstFP->getValue()));
-    } else if (Function *Func = dyn_cast<Function>(C))
-      // Hashing the name will be deterministic as LLVM's hashing infrastructure
-      // has explicit support for hashing strings and will not simply hash
-      // the pointer.
-      Hashes.emplace_back(hashArbitaryType(Func->getName()));
+    Hashes.emplace_back(I.getBitWidth());
+    for (unsigned J = 0; J < I.getNumWords(); ++J)
+      Hashes.emplace_back((I.getRawData())[J]);
----------------
ellishg wrote:

I also wonder what the difference is between `getNumWords()` and `getActiveWords()`.

```suggestion
    for (unsigned Byte : ArrayRef(I.getRawData(), I.getNumWords()))
      Hashes.emplace_back(Byte);
```

Actually, I wonder if this will work since `ArrayRef` can become a `SmallVector`. Or maybe I'm just being too fancy :)
```
Hashes.append(ArrayRef(I.getRawData(), I.getNumWords()));
```

https://github.com/llvm/llvm-project/pull/112638