[NFC] Improve debug message in getAsIntegerSet

[bondhugula]

Summary

Improve debug message in getAsIntegerSet. Add missing trailing new line
and position info.

[Groverkss]

mlir/lib/Analysis/AffineStructures.cpp

3570

I think a better way to write this would be:

local variable(s) at position var1, var2, var3 do not have an explicit representation in:

dump output

That is, print all indexes for which the representation could not be obtained.

[bondhugula]

Print all local var positions with no explicit rep.

[Groverkss]

LGTM! Thank you for this improvement.

[bondhugula]

position -> position(s)

mlir/lib/Analysis/AffineStructures.cpp

return IntegerSet::get(getNumDimIds(), getNumSymbolIds(),
                            /*eqFlags=*/true);
 
   // Construct local references.
   SmallVector<AffineExpr, 8> memo(getNumIds(), AffineExpr());
 
   if (failed(computeLocalVars(*this, memo, context))) {
     // Check if the local variables without an explicit representation have
     // zero coefficients everywhere.
-    for (unsigned i = getNumDimAndSymbolIds(), e = getNumIds(); i < e; ++i) {
-      if (!memo[i] && !isColZero(*this, /*pos=*/i)) {
-        LLVM_DEBUG(llvm::dbgs() << "one or more local exprs do not have an "
-                                   "explicit representation");
-        return IntegerSet();
-      }
-    }
-  }
+    SmallVector<unsigned> noLocalRepVars;
+    unsigned numDimsSymbols = getNumDimAndSymbolIds();
+    for (unsigned i = numDimsSymbols, e = getNumIds(); i < e; ++i) {
+      if (!memo[i] && !isColZero(*this, /*pos=*/i))
+        noLocalRepVars.push_back(i - numDimsSymbols);
+    }
+    if (!noLocalRepVars.empty()) {
+      LLVM_DEBUG({
+        llvm::dbgs() << "local variables at position(s) ";
+        llvm::interleaveComma(noLocalRepVars, llvm::dbgs());
+        llvm::dbgs() << " do not have an explicit representation in:\n";
+        this->dump();
+      });
 
   ArrayRef<AffineExpr> localExprs =
       ArrayRef<AffineExpr>(memo).take_back(getNumLocalIds());
 
   // Construct the IntegerSet from the equalities/inequalities.
   unsigned numDims = getNumDimIds();
   unsigned numSyms = getNumSymbolIds();