Simplified MinOpts GC ref tracking. (#9231)

Simplified MinOpts GC ref tracking - when a method is compiled with MinOpts for targets with the 64-bit GC info encoder we mark all GC slots as untracked and we omit encoding call sites with no live tracked GC refs explicitly in the GC tables; this can be controlled using the new COMPlus_JitMinOptsTrackGCrefs environment flag.

1 files changed, 33 insertions, 22 deletions

diff --git a/src/vm/gcinfodecoder.cpp b/src/vm/gcinfodecoder.cpp
index 89f470499e..5dd52b9fe3 100644
--- a/src/vm/gcinfodecoder.cpp
+++ b/src/vm/gcinfodecoder.cpp
@@ -628,6 +628,8 @@ bool GcInfoDecoder::EnumerateLiveSlots(
 
 
 #ifdef PARTIALLY_INTERRUPTIBLE_GC_SUPPORTED
+    bool noTrackedRefs = false;
+
     if(m_SafePointIndex < m_NumSafePoints && !executionAborted)
     {
         // Skip interruptibility information
@@ -648,33 +650,40 @@ bool GcInfoDecoder::EnumerateLiveSlots(
         //
         if(!executionAborted)
         {
-            _ASSERTE(m_NumInterruptibleRanges);
+            if(m_NumInterruptibleRanges == 0)
+            {
+                // No ranges and no explicit safepoint - must be MinOpts with untracked refs.
+                noTrackedRefs = true;
+            }
         }
 
-        int countIntersections = 0;
-        UINT32 lastNormStop = 0;
-        for(UINT32 i=0; i<m_NumInterruptibleRanges; i++)
+        if(m_NumInterruptibleRanges != 0)
         {
-            UINT32 normStartDelta = (UINT32) m_Reader.DecodeVarLengthUnsigned( INTERRUPTIBLE_RANGE_DELTA1_ENCBASE );
-            UINT32 normStopDelta = (UINT32) m_Reader.DecodeVarLengthUnsigned( INTERRUPTIBLE_RANGE_DELTA2_ENCBASE ) + 1;
+            int countIntersections = 0;
+            UINT32 lastNormStop = 0;
+            for(UINT32 i=0; i<m_NumInterruptibleRanges; i++)
+            {
+                UINT32 normStartDelta = (UINT32) m_Reader.DecodeVarLengthUnsigned( INTERRUPTIBLE_RANGE_DELTA1_ENCBASE );
+                UINT32 normStopDelta = (UINT32) m_Reader.DecodeVarLengthUnsigned( INTERRUPTIBLE_RANGE_DELTA2_ENCBASE ) + 1;
 
-            UINT32 normStart = lastNormStop + normStartDelta;
-            UINT32 normStop = normStart + normStopDelta;
-            if(normBreakOffset >= normStart && normBreakOffset < normStop)
+                UINT32 normStart = lastNormStop + normStartDelta;
+                UINT32 normStop = normStart + normStopDelta;
+                if(normBreakOffset >= normStart && normBreakOffset < normStop)
+                {
+                    _ASSERTE(pseudoBreakOffset == 0);
+                    countIntersections++;
+                    pseudoBreakOffset = numInterruptibleLength + normBreakOffset - normStart;
+                }
+                numInterruptibleLength += normStopDelta;
+                lastNormStop = normStop;
+            }        
+            _ASSERTE(countIntersections <= 1);
+            if(countIntersections == 0)
             {
-                _ASSERTE(pseudoBreakOffset == 0);
-                countIntersections++;
-                pseudoBreakOffset = numInterruptibleLength + normBreakOffset - normStart;
+                _ASSERTE(executionAborted);
+                LOG((LF_GCROOTS, LL_INFO100000, "Not reporting this frame because it is aborted and not fully interruptible.\n"));
+                goto ExitSuccess;
             }
-            numInterruptibleLength += normStopDelta;
-            lastNormStop = normStop;
-        }        
-        _ASSERTE(countIntersections <= 1);
-        if(countIntersections == 0)
-        {
-            _ASSERTE(executionAborted);
-            LOG((LF_GCROOTS, LL_INFO100000, "Not reporting this frame because it is aborted and not fully interruptible.\n"));
-            goto ExitSuccess;
         }
     }        
 #else   // !PARTIALLY_INTERRUPTIBLE_GC_SUPPORTED
@@ -718,7 +727,7 @@ bool GcInfoDecoder::EnumerateLiveSlots(
 
         if(executionAborted)
         {
-            _ASSERTE(m_NumSafePoints == 0);
+            // Skip over safepoint info (if any is present).
             m_Reader.Skip(m_NumSafePoints * numSlots);
         }
         else if( m_SafePointIndex != m_NumSafePoints )
@@ -787,6 +796,8 @@ bool GcInfoDecoder::EnumerateLiveSlots(
         else
         {
             m_Reader.Skip(m_NumSafePoints * numSlots);
+            if(noTrackedRefs)
+                goto ReportUntracked;
         }
 #endif // PARTIALLY_INTERRUPTIBLE_GC_SUPPORTED