1 files changed, 73 insertions, 29 deletions

diff --git a/lib/Transforms/IPO/InlineAlways.cpp b/lib/Transforms/IPO/InlineAlways.cpp
index c0426da..664ddf6 100644
--- a/lib/Transforms/IPO/InlineAlways.cpp
+++ b/lib/Transforms/IPO/InlineAlways.cpp
@@ -32,34 +32,21 @@ namespace {
 
   // AlwaysInliner only inlines functions that are mark as "always inline".
   class AlwaysInliner : public Inliner {
-    // Functions that are never inlined
-    SmallPtrSet<const Function*, 16> NeverInline;
-    InlineCostAnalyzer CA;
   public:
     // Use extremely low threshold.
-    AlwaysInliner() : Inliner(ID, -2000000000) {
+    AlwaysInliner() : Inliner(ID, -2000000000, /*InsertLifetime*/true) {
       initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
     }
-    static char ID; // Pass identification, replacement for typeid
-    InlineCost getInlineCost(CallSite CS) {
-      return CA.getInlineCost(CS, NeverInline);
-    }
-    float getInlineFudgeFactor(CallSite CS) {
-      return CA.getInlineFudgeFactor(CS);
-    }
-    void resetCachedCostInfo(Function *Caller) {
-      CA.resetCachedCostInfo(Caller);
-    }
-    void growCachedCostInfo(Function* Caller, Function* Callee) {
-      CA.growCachedCostInfo(Caller, Callee);
+    AlwaysInliner(bool InsertLifetime) : Inliner(ID, -2000000000,
+                                                 InsertLifetime) {
+      initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
     }
+    static char ID; // Pass identification, replacement for typeid
+    virtual InlineCost getInlineCost(CallSite CS);
     virtual bool doFinalization(CallGraph &CG) {
-      return removeDeadFunctions(CG, &NeverInline);
+      return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/true);
     }
     virtual bool doInitialization(CallGraph &CG);
-    void releaseMemory() {
-      CA.clear();
-    }
   };
 }
 
@@ -72,17 +59,74 @@ INITIALIZE_PASS_END(AlwaysInliner, "always-inline",
 
 Pass *llvm::createAlwaysInlinerPass() { return new AlwaysInliner(); }
 
-// doInitialization - Initializes the vector of functions that have not
-// been annotated with the "always inline" attribute.
-bool AlwaysInliner::doInitialization(CallGraph &CG) {
-  CA.setTargetData(getAnalysisIfAvailable<TargetData>());
+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.hasFnAttr(Attribute::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;
 
-  Module &M = CG.getModule();
+    for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;
+         ++II) {
+      CallSite CS(II);
+      if (!CS)
+        continue;
 
-  for (Module::iterator I = M.begin(), E = M.end();
-       I != E; ++I)
-    if (!I->isDeclaration() && !I->hasFnAttr(Attribute::AlwaysInline))
-      NeverInline.insert(I);
+      // 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
+/// attribute to force inlining. As such, it is dramatically simpler and avoids
+/// using the powerful (but expensive) inline cost analysis. Instead it uses
+/// a very simple and boring direct walk of the instructions looking for
+/// impossible-to-inline constructs.
+///
+/// Note, it would be possible to go to some lengths to cache the information
+/// computed here, but as we only expect to do this for relatively few and
+/// small functions which have the explicit attribute to force inlining, it is
+/// 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->hasFnAttr(Attribute::AlwaysInline))
+    return InlineCost::getNever();
+
+  // Do some minimal analysis to preclude non-viable functions.
+  if (!isInlineViable(*Callee))
+    return InlineCost::getNever();
+
+  // Otherwise, force inlining.
+  return InlineCost::getAlways();
+}
+
+// doInitialization - Initializes the vector of functions that have not
+// been annotated with the "always inline" attribute.
+bool AlwaysInliner::doInitialization(CallGraph &CG) {
   return false;
 }