[InstCombine] Don't create unnecessary zero-index GEP (NFCI)

Note needed with opaque pointers.

Author: nikic

llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp

@@ -215,27 +215,7 @@ static Instruction *simplifyAllocaArraySize(InstCombinerImpl &IC,
       New->setAlignment(AI.getAlign());
 
       replaceAllDbgUsesWith(AI, *New, *New, DT);
-
-      // 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().getIndexType(AI.getType());
-      Value *NullIdx = Constant::getNullValue(IdxTy);
-      Value *Idx[2] = {NullIdx, NullIdx};
-      Instruction *GEP = GetElementPtrInst::CreateInBounds(
-          NewTy, 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);
+      return IC.replaceInstUsesWith(AI, New);
     }
   }