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

1 files changed, 105 insertions, 71 deletions

diff --git a/lib/Analysis/InlineCost.cpp b/lib/Analysis/InlineCost.cpp
index 0da5413463..458e25503d 100644
--- a/lib/Analysis/InlineCost.cpp
+++ b/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;
   }
 
@@ -805,70 +801,69 @@ 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) {
-    // 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.
-    assert(NumInstructions == 0);
-    assert(NumVectorInstructions == 0);
-    FiftyPercentVectorBonus = Threshold;
-    TenPercentVectorBonus = Threshold / 2;
-
-    // Give out bonuses per argument, as the instructions setting them up will
-    // be gone after inlining.
-    for (unsigned I = 0, E = CS.arg_size(); I != E; ++I) {
-      if (TD && CS.isByValArgument(I)) {
-        // We approximate the number of loads and stores needed by dividing the
-        // size of the byval type by the target's pointer size.
-        PointerType *PTy = cast<PointerType>(CS.getArgument(I)->getType());
-        unsigned TypeSize = TD->getTypeSizeInBits(PTy->getElementType());
-        unsigned PointerSize = TD->getPointerSizeInBits();
-        // Ceiling division.
-        unsigned NumStores = (TypeSize + PointerSize - 1) / PointerSize;
-
-        // If it generates more than 8 stores it is likely to be expanded as an
-        // inline memcpy so we take that as an upper bound. Otherwise we assume
-        // one load and one store per word copied.
-        // FIXME: The maxStoresPerMemcpy setting from the target should be used
-        // here instead of a magic number of 8, but it's not available via
-        // DataLayout.
-        NumStores = std::min(NumStores, 8U);
-
-        Cost -= 2 * NumStores * InlineConstants::InstrCost;
-      } else {
-        // For non-byval arguments subtract off one instruction per call
-        // argument.
-        Cost -= InlineConstants::InstrCost;
-      }
+  // 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.
+  assert(NumInstructions == 0);
+  assert(NumVectorInstructions == 0);
+  FiftyPercentVectorBonus = Threshold;
+  TenPercentVectorBonus = Threshold / 2;
+
+  // Give out bonuses per argument, as the instructions setting them up will
+  // be gone after inlining.
+  for (unsigned I = 0, E = CS.arg_size(); I != E; ++I) {
+    if (TD && CS.isByValArgument(I)) {
+      // We approximate the number of loads and stores needed by dividing the
+      // size of the byval type by the target's pointer size.
+      PointerType *PTy = cast<PointerType>(CS.getArgument(I)->getType());
+      unsigned TypeSize = TD->getTypeSizeInBits(PTy->getElementType());
+      unsigned PointerSize = TD->getPointerSizeInBits();
+      // Ceiling division.
+      unsigned NumStores = (TypeSize + PointerSize - 1) / PointerSize;
+
+      // If it generates more than 8 stores it is likely to be expanded as an
+      // inline memcpy so we take that as an upper bound. Otherwise we assume
+      // one load and one store per word copied.
+      // FIXME: The maxStoresPerMemcpy setting from the target should be used
+      // here instead of a magic number of 8, but it's not available via
+      // DataLayout.
+      NumStores = std::min(NumStores, 8U);
+
+      Cost -= 2 * NumStores * InlineConstants::InstrCost;
+    } else {
+      // For non-byval arguments subtract off one instruction per call
+      // argument.
+      Cost -= InlineConstants::InstrCost;
     }
+  }
 
-    // If there is only one call of the function, and it has internal linkage,
-    // the cost of inlining it drops dramatically.
-    if (F.hasLocalLinkage() && F.hasOneUse() && &F == CS.getCalledFunction())
-      Cost += InlineConstants::LastCallToStaticBonus;
-
-    // If the instruction after the call, or if the normal destination of the
-    // invoke is an unreachable instruction, the function is noreturn. As such,
-    // there is little point in inlining this unless there is literally zero
-    // cost.
-    Instruction *Instr = CS.getInstruction();
-    if (InvokeInst *II = dyn_cast<InvokeInst>(Instr)) {
-      if (isa<UnreachableInst>(II->getNormalDest()->begin()))
-        Threshold = 1;
-    } else if (isa<UnreachableInst>(++BasicBlock::iterator(Instr)))
+  // If there is only one call of the function, and it has internal linkage,
+  // the cost of inlining it drops dramatically.
+  if (F.hasLocalLinkage() && F.hasOneUse() && &F == CS.getCalledFunction())
+    Cost += InlineConstants::LastCallToStaticBonus;
+
+  // If the instruction after the call, or if the normal destination of the
+  // invoke is an unreachable instruction, the function is noreturn. As such,
+  // there is little point in inlining this unless there is literally zero
+  // cost.
+  Instruction *Instr = CS.getInstruction();
+  if (InvokeInst *II = dyn_cast<InvokeInst>(Instr)) {
+    if (isa<UnreachableInst>(II->getNormalDest()->begin()))
       Threshold = 1;
+  } else if (isa<UnreachableInst>(++BasicBlock::iterator(Instr)))
+    Threshold = 1;
 
-    // If this function uses the coldcc calling convention, prefer not to inline
-    // it.
-    if (F.getCallingConv() == CallingConv::Cold)
-      Cost += InlineConstants::ColdccPenalty;
+  // If this function uses the coldcc calling convention, prefer not to inline
+  // it.
+  if (F.getCallingConv() == CallingConv::Cold)
+    Cost += InlineConstants::ColdccPenalty;
 
-    // Check if we're done. This can happen due to bonuses and penalties.
-    if (Cost > Threshold)
-      return false;
-  }
+  // 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;
+}