[SROA] Fix NumPromoted statistic for SROA pass (#115586)

`NumPromoted` stat should not be increased if `SROASkipMem2Reg` is set
and nothing is changed.

Author: ivafanas

llvm/lib/Transforms/Scalar/SROA.cpp

@@ -5590,12 +5590,11 @@ bool SROA::promoteAllocas(Function &F) {
   if (PromotableAllocas.empty())
     return false;
 
-  NumPromoted += PromotableAllocas.size();
-
   if (SROASkipMem2Reg) {
     LLVM_DEBUG(dbgs() << "Not promoting allocas with mem2reg!\n");
   } else {
     LLVM_DEBUG(dbgs() << "Promoting allocas with mem2reg...\n");
+    NumPromoted += PromotableAllocas.size();
     PromoteMemToReg(PromotableAllocas.getArrayRef(), DTU->getDomTree(), AC);
   }