diff --git a/src/alloy/backend/x64/lowering/lowering_sequences.cc b/src/alloy/backend/x64/lowering/lowering_sequences.cc
index 1d11baf4e..5b2cac041 100644
--- a/src/alloy/backend/x64/lowering/lowering_sequences.cc
+++ b/src/alloy/backend/x64/lowering/lowering_sequences.cc
@@ -60,6 +60,8 @@ void IssueCall(X64Emitter& e, FunctionInfo* symbol_info, uint32_t flags) {
     e.jmp(e.rax);
   } else {
     e.call(e.rax);
+    e.mov(e.rdx, e.qword[e.rsp + 8]);
+    e.mov(e.rcx, e.qword[e.rsp + 0]);
   }
 }
 
@@ -514,6 +516,8 @@ void alloy::backend::x64::lowering::RegisterSequences(LoweringTable* table) {
     e.mov(e.r8, (uint64_t)str_copy);
     e.mov(e.rax, (uint64_t)PrintString);
     e.call(e.rax);
+    e.mov(e.rdx, e.qword[e.rsp + 8]);
+    e.mov(e.rcx, e.qword[e.rsp + 0]);
     i = e.Advance(i);
     return true;
   });
@@ -624,18 +628,18 @@ void alloy::backend::x64::lowering::RegisterSequences(LoweringTable* table) {
   });
 
   table->AddSequence(OPCODE_RETURN, [](X64Emitter& e, Instr*& i) {
-    e.ret();
+    // If this is the last instruction in the last block, just let us
+    // fall through.
+    if (i->next || i->block->next) {
+      e.jmp("epilog");
+    }
     i = e.Advance(i);
     return true;
   });
 
   table->AddSequence(OPCODE_RETURN_TRUE, [](X64Emitter& e, Instr*& i) {
-    e.inLocalLabel();
     CheckBoolean(e, i->src1.value);
-    e.jne(".x", e.T_SHORT);
-    e.ret();
-    e.L(".x");
-    e.outLocalLabel();
+    e.je("epilog");
     i = e.Advance(i);
     return true;
   });
diff --git a/src/alloy/backend/x64/x64_code_cache.cc b/src/alloy/backend/x64/x64_code_cache.cc
index 76398989b..7bbf91f2a 100644
--- a/src/alloy/backend/x64/x64_code_cache.cc
+++ b/src/alloy/backend/x64/x64_code_cache.cc
@@ -214,7 +214,7 @@ void X64CodeChunk::AddTableEntry(uint8_t* code, size_t code_size) {
   offset += UNWIND_INFO_SIZE;
 
   // TODO(benvanik): take as parameters?
-  bool has_prolog = false;
+  bool has_prolog = true;
   uint8_t prolog_size = 4;
   uint8_t stack_bytes = 64;
 
diff --git a/src/alloy/backend/x64/x64_emitter.cc b/src/alloy/backend/x64/x64_emitter.cc
index 13c832621..3d6b3cfa3 100644
--- a/src/alloy/backend/x64/x64_emitter.cc
+++ b/src/alloy/backend/x64/x64_emitter.cc
@@ -119,11 +119,17 @@ int X64Emitter::Emit(HIRBuilder* builder) {
   // IMPORTANT: any changes to the prolog must be kept in sync with
   //     X64CodeCache, which dynamically generates exception information.
   //     Adding or changing anything here must be matched!
-  const bool emit_prolog = false;
+  const bool emit_prolog = true;
   const size_t stack_size = 64;
   if (emit_prolog) {
+    mov(qword[rsp + 16], rdx);
+    mov(qword[rsp + 8], rcx);
     sub(rsp, stack_size);
-    // TODO(benvanik): save registers.
+    mov(qword[rsp + 8 * 0], rbx);
+    mov(qword[rsp + 8 * 1], r12);
+    mov(qword[rsp + 8 * 2], r13);
+    mov(qword[rsp + 8 * 3], r14);
+    mov(qword[rsp + 8 * 4], r15);
   }
 
   auto lowering_table = backend_->lowering_table();
@@ -157,8 +163,12 @@ int X64Emitter::Emit(HIRBuilder* builder) {
   // Function epilog.
   L("epilog");
   if (emit_prolog) {
+    mov(rbx, qword[rsp + 8 * 0]);
+    mov(r12, qword[rsp + 8 * 1]);
+    mov(r13, qword[rsp + 8 * 2]);
+    mov(r14, qword[rsp + 8 * 3]);
+    mov(r15, qword[rsp + 8 * 4]);
     add(rsp, stack_size);
-    // TODO(benvanik): restore registers.
   }
   ret();