[MLIR][Affine] Fix affine.parallel op verifier (#127611)

Fix affine.parallel op verifier for missing check on zero result lower
or upper bound maps. lb/ub maps should have at least one result.

Fixes: #120186

Author: bondhugula

mlir/lib/Dialect/Affine/IR/AffineOps.cpp

@@ -3918,14 +3918,24 @@ LogicalResult AffineParallelOp::verify() {
   }
 
   unsigned expectedNumLBResults = 0;
-  for (APInt v : getLowerBoundsGroups())
-    expectedNumLBResults += v.getZExtValue();
+  for (APInt v : getLowerBoundsGroups()) {
+    unsigned results = v.getZExtValue();
+    if (results == 0)
+      return emitOpError()
+             << "expected lower bound map to have at least one result";
+    expectedNumLBResults += results;
+  }
   if (expectedNumLBResults != getLowerBoundsMap().getNumResults())
     return emitOpError() << "expected lower bounds map to have "
                          << expectedNumLBResults << " results";
   unsigned expectedNumUBResults = 0;
-  for (APInt v : getUpperBoundsGroups())
-    expectedNumUBResults += v.getZExtValue();
+  for (APInt v : getUpperBoundsGroups()) {
+    unsigned results = v.getZExtValue();
+    if (results == 0)
+      return emitOpError()
+             << "expected upper bound map to have at least one result";
+    expectedNumUBResults += results;
+  }
   if (expectedNumUBResults != getUpperBoundsMap().getNumResults())
     return emitOpError() << "expected upper bounds map to have "
                          << expectedNumUBResults << " results";

mlir/test/Dialect/Affine/invalid.mlir

@@ -297,6 +297,24 @@ func.func @affine_parallel(%arg0 : index, %arg1 : index, %arg2 : index) {
 
 // -----
 
+func.func @no_upper_bound_affine_parallel() {
+  // expected-error@+1 {{expected lower bound map to have at least one result}}
+  affine.parallel (%arg2) = (max()) to (1) {
+  }
+  return
+}
+
+// -----
+
+func.func @no_upper_bound_affine_parallel() {
+  // expected-error@+1 {{expected upper bound map to have at least one result}}
+  affine.parallel (%arg3) = (0) to (min()) {
+  }
+  return
+}
+
+// -----
+
 func.func @vector_load_invalid_vector_type() {
   %0 = memref.alloc() : memref<100xf32>
   affine.for %i0 = 0 to 16 step 8 {