1 files changed, 63 insertions, 20 deletions

diff --git a/lib/Transforms/IPO/InlineAlways.cpp b/lib/Transforms/IPO/InlineAlways.cpp
index 4e666fb545..a977027eed 100644
--- a/lib/Transforms/IPO/InlineAlways.cpp
+++ b/lib/Transforms/IPO/InlineAlways.cpp
@@ -32,7 +32,6 @@ 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) {
@@ -43,24 +42,7 @@ namespace {
       initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
     }
     static char ID; // Pass identification, replacement for typeid
-    InlineCost 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();
-
-      // We still have to check the inline cost in case there are reasons to
-      // not inline which trump the always-inline attribute such as setjmp and
-      // indirectbr.
-      return CA.getInlineCost(CS, getInlineThreshold(CS));
-    }
+    virtual InlineCost getInlineCost(CallSite CS);
     virtual bool doFinalization(CallGraph &CG) {
       return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/true);
     }
@@ -81,9 +63,70 @@ 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;
+
+    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
+/// 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) {
-  CA.setTargetData(getAnalysisIfAvailable<TargetData>());
   return false;
 }