[llvm] [Dexter] Implement DexStepFunction and DexContinue (PR #152721)

[Orlando Cazalet-Hyams via llvm-commits]

================
@@ -208,17 +294,96 @@ def _run_debugger_custom(self, cmdline):
                         exit_desired = True
                     bp_to_delete.append(bp_id)
                     del self._leading_bp_handles[bp_id]
-                # Add a range of trailing breakpoints covering the lines
-                # requested in the DexLimitSteps command. Ignore first line as
-                # that's covered by the leading bp we just hit and include the
-                # final line.
-                for line in range(bpr.range_from + 1, bpr.range_to + 1):
-                    self.debugger.add_breakpoint(bpr.path, line)
+
+                if bpr.function is not None:
+                    if step_info.frames:
+                        # Add this backtrace to the stack. While the current
+                        # backtrace matches the top of the stack we'll step,
+                        # and while there's a backtrace in the stack that
+                        # is a subset of the current backtrace we'll step-out.
+                        if (
+                            len(step_function_backtraces) == 0
+                            or backtrace != step_function_backtraces[-1]
+                        ):
+                            step_function_backtraces.append(backtrace)
+
+                            # Add an address breakpoint so we don't fall out
+                            # the end of nested DexStepFunctions with a DexContinue.
+                            addr = self.debugger.get_pc(frame_idx=1)
+                            instr_id = self.debugger.add_instruction_breakpoint(addr)
+                            # Note the breakpoint so we don't log the source location
+                            # it in the trace later.
+                            self.instr_bp_ids.add(instr_id)
+
+                elif bpr.is_continue:
+                    debugger_continue = True
+                    if bpr.range_to is not None:
+                        self.debugger.add_breakpoint(bpr.path, bpr.range_to)
+
+                else:
+                    # Add a range of trailing breakpoints covering the lines
+                    # requested in the DexLimitSteps command. Ignore first line as
+                    # that's covered by the leading bp we just hit and include the
+                    # final line.
+                    for line in range(bpr.range_from + 1, bpr.range_to + 1):
+                        id = self.debugger.add_breakpoint(bpr.path, line)
+                        self.context.logger.warning(
+                            f"Set trailing breakpoint {id} at {line}"
+                        )
----------------
OCHyams wrote:

```suggestion
                    for line in range(bpr.range_from + 1, bpr.range_to + 1):
                        id = self.debugger.add_breakpoint(bpr.path, line)
```

https://github.com/llvm/llvm-project/pull/152721