[InstCombine] Limit simplifyAllocaArraySize constant folding to values that fit into a uint64_t

Fixes OSS-Fuzz: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=5223

llvm-svn: 339584

1 files changed, 26 insertions, 24 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index 62769f077b4..5f0931ead49 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -197,30 +197,32 @@ static Instruction *simplifyAllocaArraySize(InstCombiner &IC, AllocaInst &AI) {
 
   // Convert: alloca Ty, C - where C is a constant != 1 into: alloca [C x Ty], 1
   if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) {
-    Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getZExtValue());
-    AllocaInst *New = IC.Builder.CreateAlloca(NewTy, nullptr, AI.getName());
-    New->setAlignment(AI.getAlignment());
-
-    // Scan to the end of the allocation instructions, to skip over a block of
-    // allocas if possible...also skip interleaved debug info
-    //
-    BasicBlock::iterator It(New);
-    while (isa<AllocaInst>(*It) || isa<DbgInfoIntrinsic>(*It))
-      ++It;
-
-    // Now that I is pointing to the first non-allocation-inst in the block,
-    // insert our getelementptr instruction...
-    //
-    Type *IdxTy = IC.getDataLayout().getIntPtrType(AI.getType());
-    Value *NullIdx = Constant::getNullValue(IdxTy);
-    Value *Idx[2] = {NullIdx, NullIdx};
-    Instruction *GEP =
-        GetElementPtrInst::CreateInBounds(New, Idx, New->getName() + ".sub");
-    IC.InsertNewInstBefore(GEP, *It);
-
-    // Now make everything use the getelementptr instead of the original
-    // allocation.
-    return IC.replaceInstUsesWith(AI, GEP);
+    if (C->getValue().getActiveBits() <= 64) {
+      Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getZExtValue());
+      AllocaInst *New = IC.Builder.CreateAlloca(NewTy, nullptr, AI.getName());
+      New->setAlignment(AI.getAlignment());
+
+      // Scan to the end of the allocation instructions, to skip over a block of
+      // allocas if possible...also skip interleaved debug info
+      //
+      BasicBlock::iterator It(New);
+      while (isa<AllocaInst>(*It) || isa<DbgInfoIntrinsic>(*It))
+        ++It;
+
+      // Now that I is pointing to the first non-allocation-inst in the block,
+      // insert our getelementptr instruction...
+      //
+      Type *IdxTy = IC.getDataLayout().getIntPtrType(AI.getType());
+      Value *NullIdx = Constant::getNullValue(IdxTy);
+      Value *Idx[2] = {NullIdx, NullIdx};
+      Instruction *GEP =
+          GetElementPtrInst::CreateInBounds(New, Idx, New->getName() + ".sub");
+      IC.InsertNewInstBefore(GEP, *It);
+
+      // Now make everything use the getelementptr instead of the original
+      // allocation.
+      return IC.replaceInstUsesWith(AI, GEP);
+    }
   }
 
   if (isa<UndefValue>(AI.getArraySize()))