Clean up handling of always-inline functions in the inliner.

This patch moves the isInlineViable function from the InlineAlways pass into
the InlineCostAnalyzer and then changes the InlineCost computation to use that
simple check for always-inline functions. All the special-case checks for
AlwaysInline in the CallAnalyzer can then go away.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168300 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/InlineCost.h

@@ -129,6 +129,9 @@ namespace llvm {
     //  Note: This is used by out-of-tree passes, please do not remove without
     //  adding a replacement API.
     InlineCost getInlineCost(CallSite CS, Function *Callee, int Threshold);
+
+    /// \brief Minimal filter to detect invalid constructs for inlining.
+    bool isInlineViable(Function &Callee);
   };
 }
 

lib/Analysis/InlineCost.cpp

@@ -49,7 +49,6 @@ class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
 
   int Threshold;
   int Cost;
-  const bool AlwaysInline;
 
   bool IsCallerRecursive;
   bool IsRecursiveCall;
@@ -128,7 +127,6 @@ class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
 public:
   CallAnalyzer(const DataLayout *TD, Function &Callee, int Threshold)
     : TD(TD), F(Callee), Threshold(Threshold), Cost(0),
-      AlwaysInline(F.getFnAttributes().hasAttribute(Attributes::AlwaysInline)),
       IsCallerRecursive(false), IsRecursiveCall(false),
       ExposesReturnsTwice(false), HasDynamicAlloca(false), AllocatedSize(0),
       NumInstructions(0), NumVectorInstructions(0),
@@ -142,7 +140,6 @@ public:
 
   int getThreshold() { return Threshold; }
   int getCost() { return Cost; }
-  bool isAlwaysInline() { return AlwaysInline; }
 
   // Keep a bunch of stats about the cost savings found so we can print them
   // out when debugging.
@@ -281,9 +278,8 @@ bool CallAnalyzer::visitAlloca(AllocaInst &I) {
                       Ty->getPrimitiveSizeInBits());
   }
 
-  // We will happily inline static alloca instructions or dynamic alloca
-  // instructions in always-inline situations.
-  if (AlwaysInline || I.isStaticAlloca())
+  // We will happily inline static alloca instructions.
+  if (I.isStaticAlloca())
     return Base::visitAlloca(I);
 
   // FIXME: This is overly conservative. Dynamic allocas are inefficient for
@@ -743,7 +739,7 @@ bool CallAnalyzer::analyzeBlock(BasicBlock *BB) {
 
     // Check if we've past the threshold so we don't spin in huge basic
     // blocks that will never inline.
-    if (!AlwaysInline && Cost > (Threshold + VectorBonus))
+    if (Cost > (Threshold + VectorBonus))
       return false;
   }
 
@@ -805,9 +801,9 @@ bool CallAnalyzer::analyzeCall(CallSite CS) {
   int SingleBBBonus = Threshold / 2;
   Threshold += SingleBBBonus;
 
-  // Unless we are always-inlining, perform some tweaks to the cost and
-  // threshold based on the direct callsite information.
-  if (!AlwaysInline) {
+  // Perform some tweaks to the cost and threshold based on the direct
+  // callsite information.
+
   // We want to more aggressively inline vector-dense kernels, so up the
   // threshold, and we'll lower it if the % of vector instructions gets too
   // low.
@@ -868,7 +864,6 @@ bool CallAnalyzer::analyzeCall(CallSite CS) {
   // Check if we're done. This can happen due to bonuses and penalties.
   if (Cost > Threshold)
     return false;
-  }
 
   if (F.empty())
     return true;
@@ -930,7 +925,7 @@ bool CallAnalyzer::analyzeCall(CallSite CS) {
   for (unsigned Idx = 0; Idx != BBWorklist.size(); ++Idx) {
     // Bail out the moment we cross the threshold. This means we'll under-count
     // the cost, but only when undercounting doesn't matter.
-    if (!AlwaysInline && Cost > (Threshold + VectorBonus))
+    if (Cost > (Threshold + VectorBonus))
       break;
 
     BasicBlock *BB = BBWorklist[Idx];
@@ -1015,7 +1010,7 @@ bool CallAnalyzer::analyzeCall(CallSite CS) {
 
   Threshold += VectorBonus;
 
-  return AlwaysInline || Cost < Threshold;
+  return Cost < Threshold;
 }
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
@@ -1040,10 +1035,22 @@ InlineCost InlineCostAnalyzer::getInlineCost(CallSite CS, int Threshold) {
 
 InlineCost InlineCostAnalyzer::getInlineCost(CallSite CS, Function *Callee,
                                              int Threshold) {
+  // Cannot inline indirect calls.
+  if (!Callee)
+    return llvm::InlineCost::getNever();
+
+  // Calls to functions with always-inline attributes should be inlined
+  // whenever possible.
+  if (Callee->getFnAttributes().hasAttribute(Attributes::AlwaysInline)) {
+    if (isInlineViable(*Callee))
+      return llvm::InlineCost::getAlways();
+    return llvm::InlineCost::getNever();
+  }
+
   // Don't inline functions which can be redefined at link-time to mean
   // something else.  Don't inline functions marked noinline or call sites
   // marked noinline.
-  if (!Callee || Callee->mayBeOverridden() ||
+  if (Callee->mayBeOverridden() ||
       Callee->getFnAttributes().hasAttribute(Attributes::NoInline) ||
       CS.isNoInline())
     return llvm::InlineCost::getNever();
@@ -1059,9 +1066,36 @@ InlineCost InlineCostAnalyzer::getInlineCost(CallSite CS, Function *Callee,
   // Check if there was a reason to force inlining or no inlining.
   if (!ShouldInline && CA.getCost() < CA.getThreshold())
     return InlineCost::getNever();
-  if (ShouldInline && (CA.isAlwaysInline() ||
-                       CA.getCost() >= CA.getThreshold()))
+  if (ShouldInline && CA.getCost() >= CA.getThreshold())
     return InlineCost::getAlways();
 
   return llvm::InlineCost::get(CA.getCost(), CA.getThreshold());
 }
+
+bool InlineCostAnalyzer::isInlineViable(Function &F) {
+  bool ReturnsTwice =F.getFnAttributes().hasAttribute(Attributes::ReturnsTwice);
+  for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
+    // Disallow inlining of functions which contain an indirect branch.
+    if (isa<IndirectBrInst>(BI->getTerminator()))
+      return false;
+
+    for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;
+         ++II) {
+      CallSite CS(II);
+      if (!CS)
+        continue;
+
+      // Disallow recursive calls.
+      if (&F == CS.getCalledFunction())
+        return false;
+
+      // Disallow calls which expose returns-twice to a function not previously
+      // attributed as such.
+      if (!ReturnsTwice && CS.isCall() &&
+          cast<CallInst>(CS.getInstruction())->canReturnTwice())
+        return false;
+    }
+  }
+
+  return true;
+}

lib/Transforms/IPO/InlineAlways.cpp

@@ -32,6 +32,7 @@ namespace {
 
   // AlwaysInliner only inlines functions that are mark as "always inline".
   class AlwaysInliner : public Inliner {
+    InlineCostAnalyzer CA;
   public:
     // Use extremely low threshold.
     AlwaysInliner() : Inliner(ID, -2000000000, /*InsertLifetime*/true) {
@@ -63,35 +64,6 @@ Pass *llvm::createAlwaysInlinerPass(bool InsertLifetime) {
   return new AlwaysInliner(InsertLifetime);
 }
 
-/// \brief Minimal filter to detect invalid constructs for inlining.
-static bool isInlineViable(Function &F) {
-  bool ReturnsTwice =F.getFnAttributes().hasAttribute(Attributes::ReturnsTwice);
-  for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
-    // Disallow inlining of functions which contain an indirect branch.
-    if (isa<IndirectBrInst>(BI->getTerminator()))
-      return false;
-
-    for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;
-         ++II) {
-      CallSite CS(II);
-      if (!CS)
-        continue;
-
-      // Disallow recursive calls.
-      if (&F == CS.getCalledFunction())
-        return false;
-
-      // Disallow calls which expose returns-twice to a function not previously
-      // attributed as such.
-      if (!ReturnsTwice && CS.isCall() &&
-          cast<CallInst>(CS.getInstruction())->canReturnTwice())
-        return false;
-    }
-  }
-
-  return true;
-}
-
 /// \brief Get the inline cost for the always-inliner.
 ///
 /// The always inliner *only* handles functions which are marked with the
@@ -106,27 +78,21 @@ static bool isInlineViable(Function &F) {
 /// likely not worth it in practice.
 InlineCost AlwaysInliner::getInlineCost(CallSite CS) {
   Function *Callee = CS.getCalledFunction();
-  // We assume indirect calls aren't calling an always-inline function.
-  if (!Callee) return InlineCost::getNever();
 
-  // We can't inline calls to external functions.
-  // FIXME: We shouldn't even get here.
-  if (Callee->isDeclaration()) return InlineCost::getNever();
-
-  // Return never for anything not marked as always inline.
-  if (!Callee->getFnAttributes().hasAttribute(Attributes::AlwaysInline))
-    return InlineCost::getNever();
-
-  // Do some minimal analysis to preclude non-viable functions.
-  if (!isInlineViable(*Callee))
-    return InlineCost::getNever();
-
-  // Otherwise, force inlining.
+  // Only inline direct calls to functions with always-inline attributes
+  // that are viable for inlining. FIXME: We shouldn't even get here for
+  // declarations.
+  if (Callee && !Callee->isDeclaration() &&
+      Callee->getFnAttributes().hasAttribute(Attributes::AlwaysInline) &&
+      CA.isInlineViable(*Callee))
     return InlineCost::getAlways();
+
+  return InlineCost::getNever();
 }
 
 // doInitialization - Initializes the vector of functions that have not
 // been annotated with the "always inline" attribute.
 bool AlwaysInliner::doInitialization(CallGraph &CG) {
+  CA.setDataLayout(getAnalysisIfAvailable<DataLayout>());
   return false;
 }