From 8deb9196ce27d08337d1c5d9c00ab20f310b37bd Mon Sep 17 00:00:00 2001
From: Andrew Au <andrewau@microsoft.com>
Date: Tue, 12 Apr 2022 18:47:04 -0700
Subject: [PATCH 1/2] Report SIP survivors

---
 src/coreclr/gc/gc.cpp   | 52 +++++++++++++++++++++++++++++++++--------
 src/coreclr/gc/gcpriv.h |  5 +++-
 2 files changed, 46 insertions(+), 11 deletions(-)

diff --git a/src/coreclr/gc/gc.cpp b/src/coreclr/gc/gc.cpp
index 9a594fbc2d4721..e280ceaaa243e9 100644
--- a/src/coreclr/gc/gc.cpp
+++ b/src/coreclr/gc/gc.cpp
@@ -32150,11 +32150,7 @@ void gc_heap::walk_relocation (void* profiling_context, record_surv_fn fn)
         generation* condemned_gen = generation_of (i);
         heap_segment*  current_heap_segment = heap_segment_rw (generation_start_segment (condemned_gen));
 #ifdef USE_REGIONS
-        while (current_heap_segment && heap_segment_swept_in_plan (current_heap_segment))
-        {
-            // TODO: Walk the heap segment and report the plugs.
-            current_heap_segment = heap_segment_next_rw (current_heap_segment);
-        }
+        current_heap_segment = walk_relocation_sip (current_heap_segment, profiling_context, fn);
         if (!current_heap_segment)
             continue;
 #endif // USE_REGIONS
@@ -32187,11 +32183,7 @@ void gc_heap::walk_relocation (void* profiling_context, record_surv_fn fn)
                 }
                 current_heap_segment = heap_segment_next_rw (current_heap_segment);
 #ifdef USE_REGIONS
-                while (current_heap_segment && heap_segment_swept_in_plan (current_heap_segment))
-                {
-                    // TODO: Walk the heap segment and report the plugs.
-                    current_heap_segment = heap_segment_next_rw (current_heap_segment);
-                }
+                current_heap_segment = walk_relocation_sip (current_heap_segment, profiling_context, fn);
 #endif // USE_REGIONS
                 if (current_heap_segment)
                 {
@@ -32218,6 +32210,46 @@ void gc_heap::walk_relocation (void* profiling_context, record_surv_fn fn)
     }
 }
 
+#ifdef USE_REGIONS
+heap_segment* gc_heap::walk_relocation_sip (heap_segment* current_heap_segment, void* profiling_context, record_surv_fn fn)
+{
+    while (current_heap_segment && heap_segment_swept_in_plan (current_heap_segment))
+    {
+        uint8_t* start = heap_segment_mem (current_heap_segment);
+        uint8_t* end = heap_segment_allocated (current_heap_segment);
+        uint8_t* obj = start;
+        uint8_t* plug_start = nullptr;
+        while (obj < end)
+        {
+            uint8_t* next_obj = obj + Align (size (obj));
+            BOOL isFree = ((CObjectHeader*)obj)->IsFree();
+            if (plug_start == nullptr)
+            {
+                if (!isFree)
+                {
+                    plug_start = obj;
+                }
+            }
+            else
+            {
+                if (isFree)
+                {
+                    fn (plug_start, obj, 0, profiling_context, false, false);
+                    plug_start = nullptr;
+                }
+            }
+            obj = next_obj;
+        }
+        if (plug_start)
+        {
+            fn (plug_start, end, 0, profiling_context, false, false);
+        }
+        current_heap_segment = heap_segment_next_rw (current_heap_segment);
+    }
+    return current_heap_segment;
+}
+#endif // USE_REGIONS
+
 void gc_heap::walk_survivors (record_surv_fn fn, void* context, walk_surv_type type)
 {
     if (type == walk_for_gc)
diff --git a/src/coreclr/gc/gcpriv.h b/src/coreclr/gc/gcpriv.h
index 0f042baa6018f1..8b364071286e0c 100644
--- a/src/coreclr/gc/gcpriv.h
+++ b/src/coreclr/gc/gcpriv.h
@@ -1647,7 +1647,10 @@ class gc_heap
 
     PER_HEAP
     void walk_relocation (void* profiling_context, record_surv_fn fn);
-
+#ifdef USE_REGIONS
+    PER_HEAP
+    heap_segment* walk_relocation_sip (heap_segment* current_heap_segment, void* profiling_context, record_surv_fn fn);
+#endif // USE_REGIONS
     PER_HEAP
     void walk_relocation_in_brick (uint8_t* tree, walk_relocate_args* args);
 

From 1ce3b374fffadc66d43e26b29ba91b6f740e0342 Mon Sep 17 00:00:00 2001
From: Andrew Au <andrewau@microsoft.com>
Date: Thu, 14 Apr 2022 08:23:41 -0700
Subject: [PATCH 2/2] Code review feedback

---
 src/coreclr/gc/gc.cpp | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/src/coreclr/gc/gc.cpp b/src/coreclr/gc/gc.cpp
index e280ceaaa243e9..64ef8a56d20e5f 100644
--- a/src/coreclr/gc/gc.cpp
+++ b/src/coreclr/gc/gc.cpp
@@ -32221,24 +32221,23 @@ heap_segment* gc_heap::walk_relocation_sip (heap_segment* current_heap_segment,
         uint8_t* plug_start = nullptr;
         while (obj < end)
         {
-            uint8_t* next_obj = obj + Align (size (obj));
-            BOOL isFree = ((CObjectHeader*)obj)->IsFree();
-            if (plug_start == nullptr)
+            if (((CObjectHeader*)obj)->IsFree())
             {
-                if (!isFree)
+                if (plug_start)
                 {
-                    plug_start = obj;
+                    fn (plug_start, obj, 0, profiling_context, false, false);
+                    plug_start = nullptr;
                 }
             }
             else
             {
-                if (isFree)
+                if (!plug_start) 
                 {
-                    fn (plug_start, obj, 0, profiling_context, false, false);
-                    plug_start = nullptr;
+                    plug_start = obj;
                 }
             }
-            obj = next_obj;
+
+            obj += Align (size (obj));
         }
         if (plug_start)
         {