[MLIR] NFC: simplify PresburgerSet::isEqual

[arjunp]

It's unclear to me, does something like this need pre-commit review?

[ftynse]

We generally use code review for everything except build unbreaks, reverts and minor syntactic changes such as typos.

[mehdi_amini]

We generally use code review for everything except build unbreaks, reverts and minor syntactic changes such as typos.

I have a more liberal view here, I've been performing refactoring and other kind of NFC or minor change without pre-commit reviews. In general many people (including me) are just reviewing a few things post-commit.

[mehdi_amini]

In D94918#2505438, @mehdi_amini wrote:

We generally use code review for everything except build unbreaks, reverts and minor syntactic changes such as typos.

I have a more liberal view here, I've been performing refactoring and other kind of NFC or minor change without pre-commit reviews. In general many people (including me) are just reviewing a few things post-commit.

I should add this is also very contextual: I wouldn't refactor linalg without asking ntv@ or the LLVM dialect without asking @zinenko, but for example such minor things in PresburgerSet made by the main authors/contributors of this component looks fine to me to land directly if they are confident enough.

mlir/lib/Analysis/PresburgerSet.cpp

 /// By "S contains T", we mean that S is a superset of or equal to T.
 ///
 /// S contains T iff T \ S is empty, since if T \ S contains a
 /// point then this is a point that is contained in T but not S.
 ///
 /// Therefore, S is equal to T iff S \ T and T \ S are both empty.
 bool PresburgerSet::isEqual(const PresburgerSet &set) const {
   assertDimensionsCompatible(set, *this);
-  PresburgerSet thisMinusSet = subtract(set);
-  if (!thisMinusSet.isIntegerEmpty())
-    return false;
-  PresburgerSet setMinusThis = set.subtract(*this);
-  return setMinusThis.isIntegerEmpty();
+  return this->subtract(set).isIntegerEmpty() &&
+         set.subtract(*this).isIntegerEmpty();
 }
 
 /// Return true if all the sets in the union are known to be integer empty,
 /// false otherwise.
 bool PresburgerSet::isIntegerEmpty() const {
   assert(nSym == 0 && "isIntegerEmpty is intended for non-symbolic sets");
   // The set is empty iff all of the disjuncts are empty.
   for (const FlatAffineConstraints &fac : flatAffineConstraints) {