[ASAN] NFC: Remove redundant variable

[Enna1]

Summary

StackAlignment has only one use: StackAlignment = std::max(StackAlignment, AI.getAlignment()); So it is redundant.

[MTC]

Thanks for the cleanup.

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
   LLVMContext *C;
   Type *IntptrTy;
   Type *IntptrPtrTy;
   ShadowMapping Mapping;
 
   SmallVector<AllocaInst *, 16> AllocaVec;
   SmallVector<AllocaInst *, 16> StaticAllocasToMoveUp;
   SmallVector<Instruction *, 8> RetVec;
-  unsigned StackAlignment;
 
   FunctionCallee AsanStackMallocFunc[kMaxAsanStackMallocSizeClass + 1],
       AsanStackFreeFunc[kMaxAsanStackMallocSizeClass + 1];
   FunctionCallee AsanSetShadowFunc[0x100] = {};
   FunctionCallee AsanPoisonStackMemoryFunc, AsanUnpoisonStackMemoryFunc;
   FunctionCallee AsanAllocaPoisonFunc, AsanAllocasUnpoisonFunc;
 
   // Stores a place and arguments of poisoning/unpoisoning call for alloca.
struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
   bool HasInlineAsm = false;
   bool HasReturnsTwiceCall = false;
   bool PoisonStack;
 
   FunctionStackPoisoner(Function &F, AddressSanitizer &ASan)
       : F(F), ASan(ASan), DIB(*F.getParent(), /*AllowUnresolved*/ false),
         C(ASan.C), IntptrTy(ASan.IntptrTy),
         IntptrPtrTy(PointerType::get(IntptrTy, 0)), Mapping(ASan.Mapping),
-        StackAlignment(1 << Mapping.Scale),
         PoisonStack(ClStack &&
                     !Triple(F.getParent()->getTargetTriple()).isAMDGPU()) {}
 
   bool runOnFunction() {
     if (!PoisonStack)
       return false;
 
     if (ClRedzoneByvalArgs)
if (!ASan.isInterestingAlloca(AI)) {
         if (AllocaVec.empty())
           return;
 
         StaticAllocasToMoveUp.push_back(&AI);
       }
       return;
     }
 
-    StackAlignment = std::max(StackAlignment, AI.getAlignment());
     if (!AI.isStaticAlloca())
       DynamicAllocaVec.push_back(&AI);
     else
       AllocaVec.push_back(&AI);
   }
 
   /// Collect lifetime intrinsic calls to check for use-after-scope
   /// errors.