Skip to content

[SelectionDAG]: Deduce KnownNeverZero from SMIN and SMAX #85722

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Mar 25, 2024
Merged

[SelectionDAG]: Deduce KnownNeverZero from SMIN and SMAX #85722

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
0d68275
[SelectionDAG]: Pre-commit tests (NFC)
AZero13 Mar 19, 2024
c44ec50
[SelectionDAG]: Deduce KnownNeverZero from SMIN and SMAX
AZero13 Mar 24, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
40 changes: 37 additions & 3 deletions llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5362,10 +5362,44 @@ bool SelectionDAG::isKnownNeverZero(SDValue Op, unsigned Depth) const {
return isKnownNeverZero(Op.getOperand(1), Depth + 1) ||
isKnownNeverZero(Op.getOperand(0), Depth + 1);

// TODO for smin/smax: If either operand is known negative/positive
// For smin/smax: If either operand is known negative/positive
// respectively we don't need the other to be known at all.
case ISD::SMAX:
case ISD::SMIN:
case ISD::SMAX: {
KnownBits Op1 = computeKnownBits(Op.getOperand(1), Depth + 1);
if (Op1.isStrictlyPositive())
return true;

KnownBits Op0 = computeKnownBits(Op.getOperand(0), Depth + 1);
if (Op0.isStrictlyPositive())
return true;

if (Op1.isNonZero() && Op0.isNonZero())
return true;

if (KnownBits::smax(Op0, Op1).isNonZero())
return true;

return isKnownNeverZero(Op.getOperand(1), Depth + 1) &&
isKnownNeverZero(Op.getOperand(0), Depth + 1);
}
case ISD::SMIN: {
KnownBits Op1 = computeKnownBits(Op.getOperand(1), Depth + 1);
if (Op1.isNegative())
return true;

KnownBits Op0 = computeKnownBits(Op.getOperand(0), Depth + 1);
if (Op0.isNegative())
return true;

if (Op1.isNonZero() && Op0.isNonZero())
return true;

if (KnownBits::smin(Op0, Op1).isNonZero())
return true;

return isKnownNeverZero(Op.getOperand(1), Depth + 1) &&
isKnownNeverZero(Op.getOperand(0), Depth + 1);
}
case ISD::UMIN:
return isKnownNeverZero(Op.getOperand(1), Depth + 1) &&
isKnownNeverZero(Op.getOperand(0), Depth + 1);
Expand Down
Loading