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[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().

llvm-svn: 355290
This commit is contained in:
Fangrui Song 2019-03-03 14:50:01 +00:00
parent e48be5d698
commit 5fa53d1593
1 changed files with 9 additions and 8 deletions
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17
llvm/lib/Analysis/DemandedBits.cpp
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@ -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);
}
}