cute test working

define i64 @main() {entry:  %a3 = alloca i64  %a4 = load i64, i64* %a3  %c8 = alloca i64  %c9 = load i64, i64* %c8  %b14 = alloca i64  %b15 = load i64, i64* %b14  br label %body0body0:  br label %if.cond1if.cond1:  %imm_store5 = add i64 1, 0  %_6 = icmp eq i64 %a4, %imm_store5  br i1 %_6, label %then.body2, label %if.exit4then.body2:  br label %then.exit3then.exit3:  br label %if.exit4if.exit4:  %b0 = phi i64 [ %b15, %if.cond1 ], [ %c9, %then.exit3 ]  br label %exitexit:  %return_reg12 = phi i64 [ %a4, %if.exit4 ]  ret i64 %return_reg12}

.auto_run_cmd.file

@@ -0,0 +1 @@
+zig test --main-pkg-path ./ ./src/ir/phi.zig

src/ir/ir_phi.zig

@@ -203,6 +203,7 @@ pub const Function = struct {
     regs: LookupTable(Register.ID, Register, Register.getID),
     cfg: CfgFunction,
     exitBBID: BasicBlock.ID,
+    retRegUsed: bool = false,
 
     /// a list of the instructions that are within the fuction
     /// the basic blocks have a list of instructions that they use,
@@ -415,7 +416,16 @@ pub const Function = struct {
 
     pub const NotFoundError = error{ OutOfMemory, UnboundIdentifier, AllocFailed };
 
-    pub fn getNamedRef(self: *Function, ir: *const IR, name: StrID, bb: IR.BasicBlock.ID) NotFoundError!Ref {
+    pub fn getNamedRef(self: *Function, ir: *const IR, name: StrID, bb: BasicBlock.ID) NotFoundError!Ref {
+        const namedRef = try self.getNamedRefInner(ir, name, bb);
+        if (self.returnReg == null) return namedRef;
+        if (namedRef.i == self.returnReg.?) {
+            self.retRegUsed = true;
+        }
+        return namedRef;
+    }
+
+    pub fn getNamedRefInner(self: *Function, ir: *const IR, name: StrID, bb: IR.BasicBlock.ID) NotFoundError!Ref {
         if (name != IR.InternPool.NULL) {
             std.debug.print("getting ref for {s}\n", .{ir.getIdent(name)});
         } else {
@@ -2112,6 +2122,11 @@ pub fn OrderedList(comptime T: type) type {
         pub fn append(self: *Self, item: T) !void {
             _ = try self.add(item);
         }
+
+        pub fn orderedRemove(self: *Self, idx: u32) T {
+            self.len -= 1;
+            return self.list.orderedRemove(idx);
+        }
     };
 }
 

src/ir/phi.zig

@@ -312,6 +312,10 @@ pub fn gen_function(
         _ = try fun.addInst(fun.exitBBID, Inst.retVoid(), .void);
     }
 
+    if (fun.retRegUsed == false and fun.returnType != .void) {
+        _ = fun.bbs.get(IR.Function.entryBBID).insts.orderedRemove(0);
+    }
+
     try fun.addCtrlFlowInst(entryBB, Inst.jmp(IR.Ref.label(fun.cfgToBBs.get(0).?)));
     return fun;
 }