JIT: Set default value for JitExtDefaultPolicyProfTrust 0 (#55229)

2 files changed, 19 insertions, 2 deletions

diff --git a/src/coreclr/jit/inlinepolicy.cpp b/src/coreclr/jit/inlinepolicy.cpp
index c328233cdf5..fdf4ae19341 100644
--- a/src/coreclr/jit/inlinepolicy.cpp
+++ b/src/coreclr/jit/inlinepolicy.cpp
@@ -1648,7 +1648,15 @@ double ExtendedDefaultPolicy::DetermineMultiplier()
         const double profileTrustCoef = (double)JitConfig.JitExtDefaultPolicyProfTrust() / 10.0;
         const double profileScale     = (double)JitConfig.JitExtDefaultPolicyProfScale() / 10.0;
 
-        multiplier *= (1.0 - profileTrustCoef) + min(m_ProfileFrequency, 1.0) * profileScale;
+        if (m_RootCompiler->fgPgoSource == ICorJitInfo::PgoSource::Dynamic)
+        {
+            // For now we only "trust" dynamic profiles.
+            multiplier *= (1.0 - profileTrustCoef) + min(m_ProfileFrequency, 1.0) * profileScale;
+        }
+        else
+        {
+            multiplier *= min(m_ProfileFrequency, 1.0) * profileScale;
+        }
         JITDUMP("\nCallsite has profile data: %g.", m_ProfileFrequency);
     }
 
diff --git a/src/coreclr/jit/jitconfigvalues.h b/src/coreclr/jit/jitconfigvalues.h
index 7527fd49221..cc10adc0b88 100644
--- a/src/coreclr/jit/jitconfigvalues.h
+++ b/src/coreclr/jit/jitconfigvalues.h
@@ -462,8 +462,17 @@ CONFIG_STRING(JitInlineReplayFile, W("JitInlineReplayFile"))
 CONFIG_INTEGER(JitExtDefaultPolicy, W("JitExtDefaultPolicy"), 1)
 CONFIG_INTEGER(JitExtDefaultPolicyMaxIL, W("JitExtDefaultPolicyMaxIL"), 0x64)
 CONFIG_INTEGER(JitExtDefaultPolicyMaxBB, W("JitExtDefaultPolicyMaxBB"), 7)
-CONFIG_INTEGER(JitExtDefaultPolicyProfScale, W("JitExtDefaultPolicyProfScale"), 0x2A)
+
+// Inliner uses the following formula for PGO-driven decisions:
+//
+//    BM = BM * ((1.0 - ProfTrust) + ProfWeight * ProfScale)
+//
+// Where BM is a benefit multiplier composed from various observations (e.g. "const arg makes a branch foldable").
+// If a profile data can be trusted for 100% we can safely just give up on inlining anything inside cold blocks
+// (except the cases where inlining in cold blocks improves type info/escape analysis for the whole caller).
+// For now, it's only applied for dynamic PGO.
 CONFIG_INTEGER(JitExtDefaultPolicyProfTrust, W("JitExtDefaultPolicyProfTrust"), 0x7)
+CONFIG_INTEGER(JitExtDefaultPolicyProfScale, W("JitExtDefaultPolicyProfScale"), 0x2A)
 
 CONFIG_INTEGER(JitInlinePolicyModel, W("JitInlinePolicyModel"), 0)
 CONFIG_INTEGER(JitInlinePolicyProfile, W("JitInlinePolicyProfile"), 0)