[llvm] r355284 - [DemandedBits] Optimize a find()+insert pattern with try_emplace and APInt::operator|=

[Fangrui Song via llvm-commits]

Author: maskray
Date: Sun Mar  3 03:12:57 2019
New Revision: 355284

URL: http://llvm.org/viewvc/llvm-project?rev=355284&view=rev
Log:
[DemandedBits] Optimize a find()+insert pattern with try_emplace and APInt::operator|=

Modified:
    llvm/trunk/lib/Analysis/DemandedBits.cpp

Modified: llvm/trunk/lib/Analysis/DemandedBits.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/DemandedBits.cpp?rev=355284&r1=355283&r2=355284&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/DemandedBits.cpp (original)
+++ llvm/trunk/lib/Analysis/DemandedBits.cpp Sun Mar  3 03:12:57 2019
@@ -402,14 +402,9 @@ void DemandedBits::performAnalysis() {
           // If we've added to the set of alive bits (or the operand has not
           // been previously visited), then re-queue the operand to be visited
           // again.
-          APInt ABPrev(BitWidth, 0);
-          auto ABI = AliveBits.find(I);
-          if (ABI != AliveBits.end())
-            ABPrev = ABI->second;
-
-          APInt ABNew = AB | ABPrev;
-          if (ABNew != ABPrev || ABI == AliveBits.end()) {
-            AliveBits[I] = std::move(ABNew);
+          auto Res = AliveBits.try_emplace(I);
+          if (Res.second || (AB |= Res.first->second) != Res.first->second) {
+            Res.first->second = std::move(AB);
             Worklist.insert(I);
           }
         }