[Lldb-commits] [lldb] [lldb][debugserver] Expedite the stopped frame's stack memory in jThreadsInfo (PR #212706)

[Yao Qi via lldb-commits]

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@@ -2733,6 +2733,76 @@ static void ReadStackMemory(nub_process_t pid, nub_thread_t tid,
   }
 }
 
+// The size of each per-side stack window we expedite.  512 is sized to cover
+// the common case (locals and params sit within a few hundred bytes) while
+// bounding the per-frame cost to 1K bytes regardless of frame size.
+static const nub_size_t k_expedite_stack_window = 512;
+
+// A single contiguous chunk of expedited memory.
+struct ExpeditedMemory {
+  nub_addr_t addr;
+  std::vector<uint8_t> bytes;
+};
+
+// Read the innermost frame's stack memory so that examining its local variables
+// at a public stop is served from the expedited cache instead of generating one
+// memory-read packet.
+//
+// We produce either:
+//
+//   - one chunk [$sp, $fp) for a small frame ($fp - $sp <=
+//   2*k_expedite_stack_window), which covers the whole frame with no gap, or
+//
+//   - two chunks [$sp, $sp + k_expedite_stack_window) and [$fp -
+//   k_expedite_stack_window, $fp) for a large frame, covering the params near
+//   $sp and the locals near $fp while leaving the (rarely-interesting) middle
+//   spill area out so the cost stays bounded.
+static void ReadFrameZeroStackMemory(nub_process_t pid, nub_thread_t tid,
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qiyao wrote:

It is a copy/paste from `ReadStackMemory`, fixed

https://github.com/llvm/llvm-project/pull/212706