I seem to relearn blr != return once every month or so.

src/alloy/hir/hir_builder.cc

@@ -642,6 +642,12 @@ void HIRBuilder::ReturnTrue(Value* cond) {
   EndBlock();
 }
 
+void HIRBuilder::SetReturnAddress(Value* value) {
+  Instr* i = AppendInstr(OPCODE_SET_RETURN_ADDRESS_info, 0);
+  i->set_src1(value);
+  i->src2.value = i->src3.value = NULL;
+}
+
 void HIRBuilder::Branch(Label* label, uint32_t branch_flags) {
   Instr* i = AppendInstr(OPCODE_BRANCH_info, branch_flags);
   i->src1.label = label;

src/alloy/hir/hir_builder.h

@@ -81,6 +81,7 @@ public:
   void CallExtern(runtime::FunctionInfo* symbol_info);
   void Return();
   void ReturnTrue(Value* cond);
+  void SetReturnAddress(Value* value);
 
   void Branch(Label* label, uint32_t branch_flags = 0);
   void Branch(Block* block, uint32_t branch_flags = 0);

src/alloy/hir/opcodes.h

@@ -18,7 +18,8 @@ namespace hir {
 
 
 enum CallFlags {
-  CALL_TAIL       = (1 << 1),
+  CALL_TAIL             = (1 << 1),
+  CALL_POSSIBLE_RETURN  = (1 << 2),
 };
 enum BranchFlags {
   BRANCH_LIKELY   = (1 << 1),
@@ -97,6 +98,7 @@ enum Opcode {
   OPCODE_CALL_EXTERN,
   OPCODE_RETURN,
   OPCODE_RETURN_TRUE,
+  OPCODE_SET_RETURN_ADDRESS,
 
   OPCODE_BRANCH,
   OPCODE_BRANCH_TRUE,

src/alloy/hir/opcodes.inl

@@ -92,6 +92,12 @@ DEFINE_OPCODE(
     OPCODE_SIG_X_V,
     OPCODE_FLAG_BRANCH);
 
+DEFINE_OPCODE(
+    OPCODE_SET_RETURN_ADDRESS,
+    "set_return_address",
+    OPCODE_SIG_X_V,
+    0);
+
 DEFINE_OPCODE(
     OPCODE_BRANCH,
     "branch",