[llvm] r355290 - [DemandedBits] Remove some redundancy in the work list

[Fangrui Song via llvm-commits]

Author: maskray
Date: Sun Mar  3 06:50:01 2019
New Revision: 355290

URL: http://llvm.org/viewvc/llvm-project?rev=355290&view=rev
Log:
[DemandedBits] Remove some redundancy in the work list

InputIsKnownDead check is shared by all operands. Compute it once.

For non-integer instructions, use Visited.insert(I).second to replace a
find() and an insert().

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=355290&r1=355289&r2=355290&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/DemandedBits.cpp (original)
+++ llvm/trunk/lib/Analysis/DemandedBits.cpp Sun Mar  3 06:50:01 2019
@@ -339,6 +339,8 @@ void DemandedBits::performAnalysis() {
         Type *T = J->getType();
         if (T->isIntOrIntVectorTy())
           AliveBits[J] = APInt::getAllOnesValue(T->getScalarSizeInBits());
+        else
+          Visited.insert(J);
         Worklist.insert(J);
       }
     }
@@ -354,16 +356,18 @@ void DemandedBits::performAnalysis() {
 
     LLVM_DEBUG(dbgs() << "DemandedBits: Visiting: " << *UserI);
     APInt AOut;
+    bool InputIsKnownDead = false;
     if (UserI->getType()->isIntOrIntVectorTy()) {
       AOut = AliveBits[UserI];
       LLVM_DEBUG(dbgs() << " Alive Out: 0x"
                         << Twine::utohexstr(AOut.getLimitedValue()));
+
+      // If all bits of the output are dead, then all bits of the input
+      // are also dead.
+      InputIsKnownDead = !AOut && !isAlwaysLive(UserI);
     }
     LLVM_DEBUG(dbgs() << "\n");
 
-    if (!UserI->getType()->isIntOrIntVectorTy())
-      Visited.insert(UserI);
-
     KnownBits Known, Known2;
     bool KnownBitsComputed = false;
     // Compute the set of alive bits for each operand. These are anded into the
@@ -380,10 +384,7 @@ void DemandedBits::performAnalysis() {
       if (T->isIntOrIntVectorTy()) {
         unsigned BitWidth = T->getScalarSizeInBits();
         APInt AB = APInt::getAllOnesValue(BitWidth);
-        if (UserI->getType()->isIntOrIntVectorTy() && !AOut &&
-            !isAlwaysLive(UserI)) {
-          // If all bits of the output are dead, then all bits of the input
-          // are also dead.
+        if (InputIsKnownDead) {
           AB = APInt(BitWidth, 0);
         } else {
           // Bits of each operand that are used to compute alive bits of the
@@ -408,7 +409,7 @@ void DemandedBits::performAnalysis() {
             Worklist.insert(I);
           }
         }
-      } else if (I && !Visited.count(I)) {
+      } else if (I && Visited.insert(I).second) {
         Worklist.insert(I);
       }
     }