[10.0-preview6] Revert "Trust single-edge synthetic profile (#116054)" (#117403)

This reverts commit ffcd1c5.

Author: AndyAyersMS

src/coreclr/jit/compiler.h

@@ -6489,7 +6489,6 @@ class Compiler
     bool                                   fgPgoSynthesized;
     bool                                   fgPgoDynamic;
     bool                                   fgPgoConsistent;
-    bool                                   fgPgoSingleEdge = false;
 
 #ifdef DEBUG
     bool                                   fgPgoDeferredInconsistency;

src/coreclr/jit/fgprofile.cpp

@@ -89,11 +89,6 @@ bool Compiler::fgHaveSufficientProfileWeights()
         case ICorJitInfo::PgoSource::Blend:
             return true;
 
-        case ICorJitInfo::PgoSource::Synthesis:
-            // Single-edge methods always have sufficient profile data.
-            // Assuming we don't synthesize value and class profile data (which we don't currently).
-            return fgPgoSingleEdge;
-
         case ICorJitInfo::PgoSource::Static:
         {
             // We sometimes call this very early, eg evaluating the prejit root.
@@ -139,12 +134,6 @@ bool Compiler::fgHaveTrustedProfileWeights()
         case ICorJitInfo::PgoSource::Blend:
         case ICorJitInfo::PgoSource::Text:
             return true;
-
-        case ICorJitInfo::PgoSource::Synthesis:
-            // Single-edge methods with synthetic profile are trustful.
-            // Assuming we don't synthesize value and class profile data (which we don't currently).
-            return fgPgoSingleEdge;
-
         default:
             return false;
     }

src/coreclr/jit/fgprofilesynthesis.cpp

@@ -148,17 +148,6 @@ void ProfileSynthesis::Run(ProfileSynthesisOption option)
     m_comp->fgPgoSynthesized = true;
     m_comp->fgPgoConsistent  = !m_approximate;
 
-    // A simple check whether the current method has more than one edge.
-    m_comp->fgPgoSingleEdge = true;
-    for (BasicBlock* const block : m_comp->Blocks())
-    {
-        if (block->NumSucc() > 1)
-        {
-            m_comp->fgPgoSingleEdge = false;
-            break;
-        }
-    }
-
     m_comp->Metrics.ProfileSynthesizedBlendedOrRepaired++;
 
     if (m_approximate)