[llvm] r233397 - [asan] Speed up isInterestingAlloca check

[Anna Zaks]

Author: zaks
Date: Fri Mar 27 13:52:01 2015
New Revision: 233397

URL: http://llvm.org/viewvc/llvm-project?rev=233397&view=rev
Log:
[asan] Speed up isInterestingAlloca check

We make many redundant calls to isInterestingAlloca in the AddressSanitzier
pass. This is especially inefficient for allocas that have many uses. Let's
cache the results to speed up compilation.

The compile time improvements depend on the input. I did not see much
difference on benchmarks; however, I have a test case where compile time
goes from minutes to under a second.

Modified:
    llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp

Modified: llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp?rev=233397&r1=233396&r2=233397&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp Fri Mar 27 13:52:01 2015
@@ -401,12 +401,12 @@ struct AddressSanitizer : public Functio
     return SizeInBytes;
   }
   /// Check if we want (and can) handle this alloca.
-  bool isInterestingAlloca(AllocaInst &AI) const;
+  bool isInterestingAlloca(AllocaInst &AI);
   /// If it is an interesting memory access, return the PointerOperand
   /// and set IsWrite/Alignment. Otherwise return nullptr.
   Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite,
                                    uint64_t *TypeSize,
-                                   unsigned *Alignment) const;
+                                   unsigned *Alignment);
   void instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis, Instruction *I,
                      bool UseCalls, const DataLayout &DL);
   void instrumentPointerComparisonOrSubtraction(Instruction *I);
@@ -458,6 +458,7 @@ struct AddressSanitizer : public Functio
   Function *AsanMemmove, *AsanMemcpy, *AsanMemset;
   InlineAsm *EmptyAsm;
   GlobalsMetadata GlobalsMD;
+  DenseMap<AllocaInst *, bool> ProcessedAllocas;
 
   friend struct FunctionStackPoisoner;
 };
@@ -804,13 +805,21 @@ void AddressSanitizer::instrumentMemIntr
 }
 
 /// Check if we want (and can) handle this alloca.
-bool AddressSanitizer::isInterestingAlloca(AllocaInst &AI) const {
-  return (AI.getAllocatedType()->isSized() &&
-          // alloca() may be called with 0 size, ignore it.
-          getAllocaSizeInBytes(&AI) > 0 &&
-          // We are only interested in allocas not promotable to registers.
-          // Promotable allocas are common under -O0.
-          (!ClSkipPromotableAllocas || !isAllocaPromotable(&AI)));
+bool AddressSanitizer::isInterestingAlloca(AllocaInst &AI) {
+  auto PreviouslySeenAllocaInfo = ProcessedAllocas.find(&AI);
+
+  if (PreviouslySeenAllocaInfo != ProcessedAllocas.end())
+    return PreviouslySeenAllocaInfo->getSecond();
+
+  bool IsInteresting = (AI.getAllocatedType()->isSized() &&
+    // alloca() may be called with 0 size, ignore it.
+    getAllocaSizeInBytes(&AI) > 0 &&
+    // We are only interested in allocas not promotable to registers.
+    // Promotable allocas are common under -O0.
+    (!ClSkipPromotableAllocas || !isAllocaPromotable(&AI)));
+
+  ProcessedAllocas[&AI] = IsInteresting;
+  return IsInteresting;
 }
 
 /// If I is an interesting memory access, return the PointerOperand
@@ -818,7 +827,7 @@ bool AddressSanitizer::isInterestingAllo
 Value *AddressSanitizer::isInterestingMemoryAccess(Instruction *I,
                                                    bool *IsWrite,
                                                    uint64_t *TypeSize,
-                                                   unsigned *Alignment) const {
+                                                   unsigned *Alignment) {
   // Skip memory accesses inserted by another instrumentation.
   if (I->getMetadata("nosanitize")) return nullptr;