Fix stepping away from the bottom-most frame of a virtual inlined cal…

…l stack. (llvm#114337)

The computation of 'Thread::IsVirtualStep" was wrong - it called being
at the bottom of a virtual call stack a "virtual step" but that is
actually when you've gotten to concrete code and need to step for real.

I also added a test for this.

lldb/source/Target/ThreadPlanStepInRange.cpp

@@ -489,7 +489,8 @@ bool ThreadPlanStepInRange::DoWillResume(lldb::StateType resume_state,
 bool ThreadPlanStepInRange::IsVirtualStep() {
   if (m_virtual_step == eLazyBoolCalculate) {
     Thread &thread = GetThread();
-    if (thread.GetCurrentInlinedDepth() == UINT32_MAX)
+    uint32_t cur_inline_depth = thread.GetCurrentInlinedDepth();
+    if (cur_inline_depth == UINT32_MAX || cur_inline_depth == 0)
       m_virtual_step = eLazyBoolNo;
     else
       m_virtual_step = eLazyBoolYes;

lldb/test/API/functionalities/inline-stepping/TestInlineStepping.py

@@ -364,7 +364,9 @@ def step_in_template(self):
         step_sequence = [["// In max_value specialized", "into"]]
         self.run_step_sequence(step_sequence)
 
-    def run_to_call_site_and_step(self, source_regex, func_name, start_pos):
+    def run_to_call_site_and_step(
+        self, source_regex, func_name, start_pos, one_more_step_loc=None
+    ):
         main_spec = lldb.SBFileSpec("calling.cpp")
         # Set the breakpoint by file and line, not sourced regex because
         # we want to make sure we can set breakpoints on call sites:
@@ -408,6 +410,14 @@ def run_to_call_site_and_step(self, source_regex, func_name, start_pos):
                 # stepping for this function...
                 break
 
+        if one_more_step_loc:
+            thread.StepInto()
+            frame_0 = thread.frame[0]
+            self.assertEqual(
+                frame_0.line_entry.line,
+                line_number(self.main_source, one_more_step_loc),
+                "Was able to step one more time",
+            )
         process.Kill()
         target.Clear()
 
@@ -420,3 +430,9 @@ def virtual_inline_stepping(self):
         self.run_to_call_site_and_step(
             "In caller_trivial_inline_2", "caller_trivial_inline_2", 3
         )
+        self.run_to_call_site_and_step(
+            "In caller_trivial_inline_3",
+            "caller_trivial_inline_3",
+            4,
+            "After caller_trivial_inline_3",
+        )

lldb/test/API/functionalities/inline-stepping/calling.cpp

@@ -95,7 +95,7 @@ void caller_trivial_inline_1() {
 
 void caller_trivial_inline_2() {
   caller_trivial_inline_3(); // In caller_trivial_inline_2.
-  inline_value += 1;
+  inline_value += 1;         // After caller_trivial_inline_3
 }
 
 void caller_trivial_inline_3() {