Tune down inlining at Osize

This is obviously just a start. Don't inline into thunks and don't inline
methods.

Start off with half the benefit for removing a call.

Author: aschwaighofer

lib/SILOptimizer/Transforms/PerformanceInliner.cpp

@@ -108,6 +108,8 @@ class SILPerformanceInliner {
     DefaultApplyLength = 10
   };
 
+  SILOptions::SILOptMode OptMode;
+
 #ifndef NDEBUG
   SILFunction *LastPrintedCaller = nullptr;
   void dumpCaller(SILFunction *Caller) {
@@ -146,8 +148,10 @@ class SILPerformanceInliner {
 
 public:
   SILPerformanceInliner(InlineSelection WhatToInline, DominanceAnalysis *DA,
-                        SILLoopAnalysis *LA, SideEffectAnalysis *SEA)
-      : WhatToInline(WhatToInline), DA(DA), LA(LA), SEA(SEA), CBI(DA) {}
+                        SILLoopAnalysis *LA, SideEffectAnalysis *SEA,
+                        SILOptions::SILOptMode OptMode)
+      : WhatToInline(WhatToInline), DA(DA), LA(LA), SEA(SEA), CBI(DA),
+        OptMode(OptMode) {}
 
   bool inlineCallsIntoFunction(SILFunction *F);
 };
@@ -170,6 +174,22 @@ bool SILPerformanceInliner::isProfitableToInline(FullApplySite AI,
 
   assert(EnableSILInliningOfGenerics || !IsGeneric);
 
+  // Start with a base benefit.
+  int BaseBenefit = RemovedCallBenefit;
+
+  // Osize heuristic.
+  if (OptMode == SILOptions::SILOptMode::OptimizeForSize) {
+    // Don't inline into thunks.
+    if (AI.getFunction()->isThunk())
+      return false;
+
+    // Don't inline methods.
+    if (Callee->getRepresentation() == SILFunctionTypeRepresentation::Method)
+      return false;
+
+    BaseBenefit = BaseBenefit / 2;
+  }
+
   // Bail out if this generic call can be optimized by means of
   // the generic specialization, because we prefer generic specialization
   // to inlining of generics.
@@ -190,21 +210,16 @@ bool SILPerformanceInliner::isProfitableToInline(FullApplySite AI,
   int CalleeCost = 0;
   int Benefit = 0;
 
-  // Start with a base benefit.
-  int BaseBenefit = RemovedCallBenefit;
-
   SubstitutionMap CalleeSubstMap;
   if (IsGeneric) {
     CalleeSubstMap = Callee->getLoweredFunctionType()
       ->getGenericSignature()
       ->getSubstitutionMap(AI.getSubstitutions());
   }
 
-  const SILOptions &Opts = Callee->getModule().getOptions();
-
   // For some reason -Ounchecked can accept a higher base benefit without
   // increasing the code size too much.
-  if (Opts.Optimization == SILOptions::SILOptMode::OptimizeUnchecked)
+  if (OptMode == SILOptions::SILOptMode::OptimizeUnchecked)
     BaseBenefit *= 2;
 
   CallerWeight.updateBenefit(Benefit, BaseBenefit);
@@ -696,7 +711,9 @@ class SILPerformanceInlinerPass : public SILFunctionTransform {
       return;
     }
 
-    SILPerformanceInliner Inliner(WhatToInline, DA, LA, SEA);
+    auto OptMode = getFunction()->getModule().getOptions().Optimization;
+
+    SILPerformanceInliner Inliner(WhatToInline, DA, LA, SEA, OptMode);
 
     assert(getFunction()->isDefinition() &&
            "Expected only functions with bodies!");