[inliner] Fix the early-exit of the inline cost analysis to correctly

[oota-llvm.git] / lib / Analysis / IPA / InlineCost.cpp

diff --git a/lib/Analysis/IPA/InlineCost.cpp b/lib/Analysis/IPA/InlineCost.cpp
index cacf70d041bf6a69c1ec1caca0a951c8f8b2d2fc..2bd959d85343df19a617ac7c35657db2be2e350b 100644 (file)
--- a/lib/Analysis/IPA/InlineCost.cpp
+++ b/lib/Analysis/IPA/InlineCost.cpp
@@ -955,16 +955,9 @@ bool CallAnalyzer::analyzeBlock(BasicBlock *BB,
         AllocatedSize > InlineConstants::TotalAllocaSizeRecursiveCaller)
       return false;
 
-    if (NumVectorInstructions > NumInstructions/2)
-      VectorBonus = FiftyPercentVectorBonus;
-    else if (NumVectorInstructions > NumInstructions/10)
-      VectorBonus = TenPercentVectorBonus;
-    else
-      VectorBonus = 0;
-
-    // Check if we've past the threshold so we don't spin in huge basic
-    // blocks that will never inline.
-    if (Cost > (Threshold + VectorBonus))
+    // Check if we've past the maximum possible threshold so we don't spin in
+    // huge basic blocks that will never inline.
+    if (Cost > Threshold)
       return false;
   }
 
@@ -1020,25 +1013,33 @@ ConstantInt *CallAnalyzer::stripAndComputeInBoundsConstantOffsets(Value *&V) {
 bool CallAnalyzer::analyzeCall(CallSite CS) {
   ++NumCallsAnalyzed;
 
-  // Track whether the post-inlining function would have more than one basic
-  // block. A single basic block is often intended for inlining. Balloon the
-  // threshold by 50% until we pass the single-BB phase.
-  bool SingleBB = true;
-  int SingleBBBonus = Threshold / 2;
-  Threshold += SingleBBBonus;
-
   // 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.
+  // low. Note that these bonuses are some what arbitrary and evolved over time
+  // by accident as much as because they are principled bonuses.
+  //
+  // FIXME: It would be nice to remove all such bonuses. At least it would be
+  // nice to base the bonus values on something more scientific.
   assert(NumInstructions == 0);
   assert(NumVectorInstructions == 0);
-  FiftyPercentVectorBonus = Threshold;
-  TenPercentVectorBonus = Threshold / 2;
+  FiftyPercentVectorBonus = 3 * Threshold / 2;
+  TenPercentVectorBonus = 3 * Threshold / 4;
   const DataLayout &DL = F.getParent()->getDataLayout();
 
+  // Track whether the post-inlining function would have more than one basic
+  // block. A single basic block is often intended for inlining. Balloon the
+  // threshold by 50% until we pass the single-BB phase.
+  bool SingleBB = true;
+  int SingleBBBonus = Threshold / 2;
+
+  // Speculatively apply all possible bonuses to Threshold. If cost exceeds
+  // this Threshold any time, and cost cannot decrease, we can stop processing
+  // the rest of the function body.
+  Threshold += (SingleBBBonus + FiftyPercentVectorBonus);
+
   // 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) {
@@ -1081,9 +1082,9 @@ bool CallAnalyzer::analyzeCall(CallSite CS) {
   Instruction *Instr = CS.getInstruction();
   if (InvokeInst *II = dyn_cast<InvokeInst>(Instr)) {
     if (isa<UnreachableInst>(II->getNormalDest()->begin()))
-      Threshold = 1;
+      Threshold = 0;
   } else if (isa<UnreachableInst>(++BasicBlock::iterator(Instr)))
-    Threshold = 1;
+    Threshold = 0;
 
   // If this function uses the coldcc calling convention, prefer not to inline
   // it.
@@ -1155,7 +1156,7 @@ 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 (Cost > (Threshold + VectorBonus))
+    if (Cost > Threshold)
       break;
 
     BasicBlock *BB = BBWorklist[Idx];
@@ -1233,7 +1234,13 @@ bool CallAnalyzer::analyzeCall(CallSite CS) {
   if (!OnlyOneCallAndLocalLinkage && ContainsNoDuplicateCall)
     return false;
 
-  Threshold += VectorBonus;
+  // We applied the maximum possible vector bonus at the beginning. Now,
+  // subtract the excess bonus, if any, from the Threshold before
+  // comparing against Cost.
+  if (NumVectorInstructions <= NumInstructions / 10)
+    Threshold -= FiftyPercentVectorBonus;
+  else if (NumVectorInstructions <= NumInstructions / 2)
+    Threshold -= (FiftyPercentVectorBonus - TenPercentVectorBonus);
 
   return Cost < Threshold;
 }
@@ -1248,12 +1255,12 @@ void CallAnalyzer::dump() {
   DEBUG_PRINT_STAT(NumConstantPtrCmps);
   DEBUG_PRINT_STAT(NumConstantPtrDiffs);
   DEBUG_PRINT_STAT(NumInstructionsSimplified);
+  DEBUG_PRINT_STAT(NumInstructions);
   DEBUG_PRINT_STAT(SROACostSavings);
   DEBUG_PRINT_STAT(SROACostSavingsLost);
   DEBUG_PRINT_STAT(ContainsNoDuplicateCall);
   DEBUG_PRINT_STAT(Cost);
   DEBUG_PRINT_STAT(Threshold);
-  DEBUG_PRINT_STAT(VectorBonus);
 #undef DEBUG_PRINT_STAT
 }
 #endif