YJIT: jit_prepare_routine_call() for String#+@ missing

We saw SEGVs due to this when running with StackProf, which needs a
correct PC for RUBY_INTERNAL_EVENT_NEWOBJ, the same event used for
ObjectSpace allocation tracing.

[Bug #19444]

test/ruby/test_yjit.rb

@@ -1092,6 +1092,33 @@ class TestYJIT < Test::Unit::TestCase
     RUBY
   end
 
+  def test_tracing_str_uplus
+    assert_compiles(<<~RUBY, frozen_string_literal: true, result: :ok)
+      def str_uplus
+        _ = 1
+        _ = 2
+        ret = [+"frfr", __LINE__]
+        _ = 3
+        _ = 4
+
+        ret
+      end
+
+      str_uplus
+      require 'objspace'
+      ObjectSpace.trace_object_allocations_start
+
+      str, expected_line = str_uplus
+      alloc_line = ObjectSpace.allocation_sourceline(str)
+
+      if expected_line == alloc_line
+        :ok
+      else
+        [expected_line, alloc_line]
+      end
+    RUBY
+  end
+
   private
 
   def code_gc_helpers

yjit/src/codegen.rs

@@ -4157,7 +4157,7 @@ fn jit_rb_int_equal(
 
 /// If string is frozen, duplicate it to get a non-frozen string. Otherwise, return it.
 fn jit_rb_str_uplus(
-    _jit: &mut JITState,
+    jit: &mut JITState,
     ctx: &mut Context,
     asm: &mut Assembler,
     _ocb: &mut OutlinedCb,
@@ -4168,6 +4168,9 @@ fn jit_rb_str_uplus(
     _known_recv_class: *const VALUE,
 ) -> bool
 {
+    // We allocate when we dup the string
+    jit_prepare_routine_call(jit, ctx, asm);
+
     asm.comment("Unary plus on string");
     let recv_opnd = asm.load(ctx.stack_pop(1));
     let flags_opnd = asm.load(Opnd::mem(64, recv_opnd, RUBY_OFFSET_RBASIC_FLAGS));