[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.

llvm-svn: 233397

1 files changed, 19 insertions, 10 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index 978c8570239..f29fd050806 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -401,12 +401,12 @@ struct AddressSanitizer : public FunctionPass {
     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 FunctionPass {
   Function *AsanMemmove, *AsanMemcpy, *AsanMemset;
   InlineAsm *EmptyAsm;
   GlobalsMetadata GlobalsMD;
+  DenseMap<AllocaInst *, bool> ProcessedAllocas;
 
   friend struct FunctionStackPoisoner;
 };
@@ -804,13 +805,21 @@ void AddressSanitizer::instrumentMemIntrinsic(MemIntrinsic *MI) {
 }
 
 /// 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::isInterestingAlloca(AllocaInst &AI) const {
 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;