diff --git a/llvm/include/llvm/CodeGen/Passes.h b/llvm/include/llvm/CodeGen/Passes.h
--- a/llvm/include/llvm/CodeGen/Passes.h
+++ b/llvm/include/llvm/CodeGen/Passes.h
@@ -578,6 +578,9 @@
   /// otherwise this does nothing
   FunctionPass *createRegAllocScoringPass();
 
+  // When learning an eviction policy, export basic blocks and profile info
+  FunctionPass *createRegAllocBBProfileDumpPass();
+
   /// JMC instrument pass.
   ModulePass *createJMCInstrumenterPass();
 
diff --git a/llvm/include/llvm/InitializePasses.h b/llvm/include/llvm/InitializePasses.h
--- a/llvm/include/llvm/InitializePasses.h
+++ b/llvm/include/llvm/InitializePasses.h
@@ -337,6 +337,7 @@
 void initializeRegAllocFastPass(PassRegistry&);
 void initializeRegAllocPriorityAdvisorAnalysisPass(PassRegistry &);
 void initializeRegAllocScoringPass(PassRegistry &);
+void initializeRegAllocBBProfileDumpPass(PassRegistry &);
 void initializeRegBankSelectPass(PassRegistry&);
 void initializeRegToMemLegacyPass(PassRegistry&);
 void initializeRegUsageInfoCollectorPass(PassRegistry&);
diff --git a/llvm/lib/CodeGen/MLRegallocEvictAdvisor.cpp b/llvm/lib/CodeGen/MLRegallocEvictAdvisor.cpp
--- a/llvm/lib/CodeGen/MLRegallocEvictAdvisor.cpp
+++ b/llvm/lib/CodeGen/MLRegallocEvictAdvisor.cpp
@@ -70,6 +70,10 @@
     cl::desc("Whether or not to enable features under development for the ML "
              "regalloc advisor"));
 
+static cl::opt<std::string> BasicBlockProfileDump(
+    "regalloc-bb-profile-dump", cl::Hidden,
+    cl::desc("Basic block profile dump for external cost modelling"));
+
 #else
 static const bool EnableDevelopmentFeatures = false;
 #endif // #ifdef LLVM_HAVE_TFLITE
@@ -115,6 +119,55 @@
 INITIALIZE_PASS(RegAllocScoring, "regallocscoringpass",
                 "Register Allocation Scoring Pass", false, false)
 
+// The BB frequency/mc dump pass.
+// This dumps the basic blocks along with some frequency info right before
+// assembly printing time so that they can be processed by an external cost
+// model.
+// This only happens in development mode with a flag. It's a no-op otherwise.
+namespace llvm {
+class RegAllocBBProfileDump : public MachineFunctionPass {
+public:
+  static char ID;
+  std::unique_ptr<raw_fd_ostream> FileOutput;
+
+  RegAllocBBProfileDump() : MachineFunctionPass(ID) {
+    initializeRegAllocBBProfileDumpPass(*PassRegistry::getPassRegistry());
+    if(!BasicBlockProfileDump.empty()) {
+      std::error_code PossibleFileError;
+      FileOutput = std::make_unique<raw_fd_ostream>(BasicBlockProfileDump,
+                                                    PossibleFileError);
+    }
+  }
+
+  ~RegAllocBBProfileDump() override {
+    if(FileOutput) {
+      FileOutput->close(); 
+    }
+  }
+
+  StringRef getPassName() const override {
+    return "Register Allocation BB Profile Dump";
+  }
+
+  // Analysis usage
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesAll();
+    AU.addRequired<MachineBlockFrequencyInfo>();
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+
+  // Perform the pass
+  bool runOnMachineFunction(MachineFunction &) override;
+};
+
+char RegAllocBBProfileDump::ID = 0;
+FunctionPass *createRegAllocBBProfileDumpPass() { return new RegAllocBBProfileDump(); }
+
+} // namespace llvm
+
+INITIALIZE_PASS(RegAllocBBProfileDump, "regallocbbdump", "Register Allocation BB Dump",
+                false, false)
+
 // ===================================
 // Common ML Advisor declarations
 // ===================================
@@ -1128,6 +1181,18 @@
                                                                    GetReward);
   return false;
 }
+
+bool RegAllocBBProfileDump::runOnMachineFunction(MachineFunction &MF) {
+  if (!BasicBlockProfileDump.empty()) {
+    MachineBlockFrequencyInfo &MBFI = getAnalysis<MachineBlockFrequencyInfo>();
+    for (auto &MBB : MF) {
+      *FileOutput.get() << MF.getName() << ","
+                        << MBB.getNumber() << ","
+                        << MBFI.getBlockFreqRelativeToEntryBlock(&MBB) << "\n";
+    }
+  }
+  return false;
+}
 #endif // #ifdef LLVM_HAVE_TFLITE
 
 RegAllocEvictionAdvisorAnalysis *llvm::createReleaseModeAdvisor() {
@@ -1137,4 +1202,5 @@
 // In all cases except development mode, we don't need scoring.
 #if !defined(LLVM_HAVE_TFLITE)
 bool RegAllocScoring::runOnMachineFunction(MachineFunction &) { return false; }
+bool RegAllocBBProfileDump::runOnMachineFunction(MachineFunction &) { return false; }
 #endif
diff --git a/llvm/lib/CodeGen/TargetPassConfig.cpp b/llvm/lib/CodeGen/TargetPassConfig.cpp
--- a/llvm/lib/CodeGen/TargetPassConfig.cpp
+++ b/llvm/lib/CodeGen/TargetPassConfig.cpp
@@ -1273,6 +1273,9 @@
   // Add passes that directly emit MI after all other MI passes.
   addPreEmitPass2();
 
+  // Export basic blocks for training ML Regalloc models
+  addPass(createRegAllocBBProfileDumpPass());
+
   AddingMachinePasses = false;
 }
 
diff --git a/llvm/test/CodeGen/MLRegalloc/bb-profile-dump.ll b/llvm/test/CodeGen/MLRegalloc/bb-profile-dump.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/MLRegalloc/bb-profile-dump.ll
@@ -0,0 +1,21 @@
+; REQUIRES: have_tflite
+; REQUIRES: default_triple
+;
+; Check that the basic block profile dump outputs data and in the correct
+; format.
+;
+; RUN: llc -o /dev/null -regalloc-enable-advisor=release -regalloc-bb-profile-dump=%t %s
+; RUN: FileCheck --input-file %t %s
+
+define i64 @f2(i64 %a, i64 %b) {
+    %sum = add i64 %a, %b
+    ret i64 %sum
+}
+
+define i64 @f1() {
+    %sum = call i64 @f2(i64 2, i64 2)
+    ret i64 %sum
+}
+
+; CHECK: f2,0,1.000000e+00
+; CHECK-NEXT: f1,0,1.000000e+00