JIT: prefer edge counts; keep class profiles even if tossing counts (#85406)

If there are both edge and block counts for a method, prefer to use the
edge counts (block counts are no longer the default, so are more likely
to be stale).

Sometimes we decide not to use count data because of correlation or
solver issues. When this happens, keep the class profile data viable
and let the code that deals with class profiles handle the possibility
of stale or mismatched data.

Addresses some aspects of #84446, though it's still not clear why we see
static profiles with both block and edge counts.

diff --git a/src/coreclr/jit/fgprofile.cpp b/src/coreclr/jit/fgprofile.cpp
index a856a72..39c16f1 100644 (file)
--- a/src/coreclr/jit/fgprofile.cpp
+++ b/src/coreclr/jit/fgprofile.cpp
@@ -2707,29 +2707,19 @@ PhaseStatus Compiler::fgIncorporateProfileData()
 
     if (fgPgoHaveWeights)
     {
-        // We expect not to have both block and edge counts. We may have other
-        // forms of profile data even if we do not have any counts.
+        // If for some reason we have both block and edge counts, prefer the edge counts.
         //
-        // As of 4/6/2023 the following invariant check turns out to no longer hold.
-        // Tracking issue: https://github.com/dotnet/runtime/issues/84446
-        //
-        // assert(!haveBlockCounts || !haveEdgeCounts);
-
         bool dataIsGood = false;
 
-        if (haveBlockCounts)
+        if (haveEdgeCounts)
         {
-            dataIsGood = fgIncorporateBlockCounts();
+            dataIsGood = fgIncorporateEdgeCounts();
         }
-        else if (haveEdgeCounts)
+        else if (haveBlockCounts)
         {
-            dataIsGood = fgIncorporateEdgeCounts();
+            dataIsGood = fgIncorporateBlockCounts();
         }
 
-        // Profile incorporation may have tossed out all PGO data if it
-        // encountered major issues. This is perhaps too drastic. Consider
-        // at least keeping the class profile data, or perhaps enable full synthesis.
-        //
         // If profile incorporation hit fixable problems, run synthesis in blend mode.
         //
         if (fgPgoHaveWeights && !dataIsGood)
@@ -3554,10 +3544,9 @@ void EfficientEdgeCountReconstructor::Propagate()
     //
     if (m_badcode || m_mismatch || m_failedToConverge || m_allWeightsZero)
     {
-        // Make sure nothing else in the jit looks at the profile data.
+        // Make sure nothing else in the jit looks at the count profile data.
         //
         m_comp->fgPgoHaveWeights = false;
-        m_comp->fgPgoSchema      = nullptr;
 
         if (m_badcode)
         {
@@ -3576,7 +3565,7 @@ void EfficientEdgeCountReconstructor::Propagate()
             m_comp->fgPgoFailReason = "PGO data available, profile data was all zero";
         }
 
-        JITDUMP("... discarding profile data: %s\n", m_comp->fgPgoFailReason);
+        JITDUMP("... discarding profile count data: %s\n", m_comp->fgPgoFailReason);
         return;
     }