[DAGCombiner] Transform ABS(X) eq/ne 0/IntMin -> X eq/ne 0/IntMIn

[goldstein.w.n]

Summary

This is done by the middle end generally so probably rarely applied,
but was brought up in D142345 and if it is hit, does some good.

Alive2:
https://alive2.llvm.org/ce/z/KgyhbS
https://alive2.llvm.org/ce/z/HLhHLe
https://alive2.llvm.org/ce/z/8FtEZ4
https://alive2.llvm.org/ce/z/h_NDHa
https://alive2.llvm.org/ce/z/v7DotM
https://alive2.llvm.org/ce/z/G29gj4
https://alive2.llvm.org/ce/z/yZWEzu
https://alive2.llvm.org/ce/z/RFs4iC

[RKSimon]

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

11698

Isn't ISD::ABS always one operand? We don't have the INT_MIN handling in the DAG node:

/// ABS - Determine the unsigned absolute value of a signed integer value of
/// the same bitwidth.
/// Note: A value of INT_MIN will return INT_MIN, no saturation or overflow
/// is performed.
ABS,

[goldstein.w.n]

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

11698

Isn't ISD::ABS always one operand? We don't have the INT_MIN handling in the DAG node:

/// ABS - Determine the unsigned absolute value of a signed integer value of
/// the same bitwidth.
/// Note: A value of INT_MIN will return INT_MIN, no saturation or overflow
/// is performed.
ABS,

You're right, will fix if go forward with the patch, although based on the comment in D142345 I think the consensus with this is truly unneeded so will likely abandon.