[NFC] Add a ConstantInitBuilder method to add a UniqueHash

structure for a string

Author: rjmccall

lib/IRGen/ConstantBuilder.h

@@ -156,6 +156,10 @@ class ConstantAggregateBuilderBase
   void addSignedPointer(llvm::Constant *pointer,
                         const clang::PointerAuthSchema &schema,
                         uint16_t otherDiscriminator);
+
+  /// Add a UniqueHash metadata structure to this builder which stores
+  /// a hash of the given string.
+  void addUniqueHash(StringRef ofString);
 };
 
 class ConstantArrayBuilder

lib/IRGen/GenConstant.cpp

@@ -23,8 +23,10 @@
 #include "TypeInfo.h"
 #include "StructLayout.h"
 #include "Callee.h"
+#include "ConstantBuilder.h"
 #include "swift/Basic/Range.h"
 #include "swift/SIL/SILModule.h"
+#include "llvm/Support/BLAKE3.h"
 
 using namespace swift;
 using namespace irgen;
@@ -282,3 +284,11 @@ llvm::Constant *irgen::emitConstantObject(IRGenModule &IGM, ObjectInst *OI,
   insertPadding(elts, sTy);
   return llvm::ConstantStruct::get(sTy, elts);
 }
+
+void ConstantAggregateBuilderBase::addUniqueHash(StringRef data) {
+  llvm::BLAKE3 hasher;
+  hasher.update(data);
+  auto rawHash = hasher.final();
+  auto truncHash = llvm::makeArrayRef(rawHash).slice(0, NumBytes_UniqueHash);
+  add(llvm::ConstantDataArray::get(IGM().getLLVMContext(), truncHash));
+}