JIT: boost inlining when callee unboxes an arg

src/coreclr/jit/fgbasic.cpp

@@ -1056,6 +1056,24 @@ void Compiler::fgFindJumpTargets(const BYTE* codeAddr, IL_OFFSET codeSize, Fixed
                 break;
             }
 
+            case CEE_UNBOX:
+            case CEE_UNBOX_ANY:
+            {
+                if (makeInlineObservations)
+                {
+                    FgStack::FgSlot slot = pushedStack.Top();
+                    if (FgStack::IsExactArgument(slot, impInlineInfo))
+                    {
+                        compInlineResult->Note(InlineObservation::CALLSITE_UNBOX_EXACT_ARG);
+                    }
+                    else if (FgStack::IsArgument(slot))
+                    {
+                        compInlineResult->Note(InlineObservation::CALLEE_UNBOX_ARG);
+                    }
+                }
+                break;
+            }
+
             case CEE_CASTCLASS:
             case CEE_ISINST:
             {

src/coreclr/jit/inline.def

@@ -106,6 +106,7 @@ INLINE_OBSERVATION(NUMBER_OF_ARGUMENTS,       int,    "number of arguments",
 INLINE_OBSERVATION(NUMBER_OF_BASIC_BLOCKS,    int,    "number of basic blocks",               INFORMATION, CALLEE)
 INLINE_OBSERVATION(NUMBER_OF_LOCALS,          int,    "number of locals",                     INFORMATION, CALLEE)
 INLINE_OBSERVATION(RANDOM_ACCEPT,             bool,   "random accept",                        INFORMATION, CALLEE)
+INLINE_OBSERVATION(UNBOX_ARG,                 int,    "callee unboxes arg",                   INFORMATION, CALLEE)
 INLINE_OBSERVATION(UNSUPPORTED_OPCODE,        bool,   "unsupported opcode",                   INFORMATION, CALLEE)
 
 // ------ Caller Correctness -------
@@ -194,6 +195,7 @@ INLINE_OBSERVATION(LOG_REPLAY_ACCEPT,         bool,   "accepted by log replay",
 INLINE_OBSERVATION(PROFILE_FREQUENCY,         double, "frequency from profile data",          INFORMATION, CALLSITE)
 INLINE_OBSERVATION(RANDOM_ACCEPT,             bool,   "random accept",                        INFORMATION, CALLSITE)
 INLINE_OBSERVATION(WEIGHT,                    int,    "frequency from block weight",          INFORMATION, CALLSITE)
+INLINE_OBSERVATION(UNBOX_EXACT_ARG,           int,    "unbox of arg with exact class",        INFORMATION, CALLSITE)
 
 // ------ Final Sentinel -------
 

src/coreclr/jit/inlinepolicy.cpp

@@ -1362,6 +1362,14 @@ void ExtendedDefaultPolicy::NoteBool(InlineObservation obs, bool value)
             m_IsCallsiteInNoReturnRegion = value;
             break;
 
+        case InlineObservation::CALLEE_UNBOX_ARG:
+            m_ArgUnbox++;
+            break;
+
+        case InlineObservation::CALLSITE_UNBOX_EXACT_ARG:
+            m_ArgUnboxExact++;
+            break;
+
         default:
             DefaultPolicy::NoteBool(obs, value);
             break;
@@ -1716,6 +1724,30 @@ double ExtendedDefaultPolicy::DetermineMultiplier()
         JITDUMP("\nPrejit root candidate has arg that feeds a conditional.  Multiplier increased to %g.", multiplier);
     }
 
+    if (m_ArgUnboxExact > 0)
+    {
+        // Callee has unbox(arg), caller supplies exact type (a box)
+        // We can likely optimize
+        multiplier += 4.0;
+        JITDUMP("\nInline candidate has %d exact arg unboxes.  Multiplier increased to %g.", m_ArgUnboxExact,
+                multiplier);
+    }
+
+    if (m_ArgUnbox > 0)
+    {
+        // Callee has unbox(arg), caller arg not known type
+        if (m_IsPrejitRoot)
+        {
+            // Assume these might be met with exact type args
+            multiplier += 4.0;
+        }
+        else
+        {
+            multiplier += 1.0;
+        }
+        JITDUMP("\nInline candidate has %d arg unboxes.  Multiplier increased to %g.", m_ArgUnboxExact, multiplier);
+    }
+
     switch (m_CallsiteFrequency)
     {
         case InlineCallsiteFrequency::RARE:

src/coreclr/jit/inlinepolicy.h

@@ -219,6 +219,8 @@ class ExtendedDefaultPolicy : public DefaultPolicy
         , m_UnrollableMemop(0)
         , m_Switch(0)
         , m_DivByCns(0)
+        , m_ArgUnbox(0)
+        , m_ArgUnboxExact(0)
         , m_ReturnsStructByValue(false)
         , m_IsFromValueClass(false)
         , m_NonGenericCallsGeneric(false)
@@ -272,6 +274,8 @@ class ExtendedDefaultPolicy : public DefaultPolicy
     unsigned m_UnrollableMemop;
     unsigned m_Switch;
     unsigned m_DivByCns;
+    unsigned m_ArgUnbox;
+    unsigned m_ArgUnboxExact;
     bool     m_ReturnsStructByValue       : 1;
     bool     m_IsFromValueClass           : 1;
     bool     m_NonGenericCallsGeneric     : 1;