[AMDGPU] Avoid repeated hash lookups (NFC) (#112309)

Author: kazutakahirata

llvm/lib/Target/AMDGPU/SIOptimizeVGPRLiveRange.cpp

@@ -189,7 +189,7 @@ void SIOptimizeVGPRLiveRange::collectElseRegionBlocks(
   unsigned Cur = 0;
   while (MBB) {
     for (auto *Pred : MBB->predecessors()) {
-      if (Pred != Flow && !Blocks.contains(Pred))
+      if (Pred != Flow)
         Blocks.insert(Pred);
     }
 
@@ -407,10 +407,8 @@ void SIOptimizeVGPRLiveRange::updateLiveRangeInThenRegion(
   while (!WorkList.empty()) {
     auto *MBB = WorkList.pop_back_val();
     for (auto *Succ : MBB->successors()) {
-      if (Succ != Flow && !Blocks.contains(Succ)) {
+      if (Succ != Flow && Blocks.insert(Succ))
         WorkList.push_back(Succ);
-        Blocks.insert(Succ);
-      }
     }
   }