[mlir][affine] Prevent vectorizer test from crash without any map

[Lewuathe]

Summary

If the vectorizer test pass does not get any affine map, it should output nothing instead of crash.

Issue: https://github.com/llvm/llvm-project/issues/61534

[Lewuathe]

Add new line.

[Lewuathe]

Remove debug code.

[nicolasvasilache]

thanks!

mlir/test/Dialect/Affine/SuperVectorize/compose_maps.mlir

 // -----
 
 func.func @multi_symbols() {
   // CHECK: Composed map: (d0)[s0, s1, s2] -> (d0 + s1 + s2 + 1, d0 - s0 - s2 - 1)
   "test_affine_map"() { affine_map = affine_map<(d0)[s0] -> (d0 + s0, d0 - s0)> } : () -> ()
   "test_affine_map"() { affine_map = affine_map<(d0, d1)[s0, s1] -> (d0 + 1 + s1, d1 - 1 - s0)> } : () -> ()
   return
 }
+
+// -----
+
+// CHECK-LABEL: @no_affine_maps
+func.func @no_affine_maps() {
+  // CHECK: return
+  return
+}

mlir/test/lib/Dialect/Affine/TestVectorizationUtils.cpp

void VectorizerTestPass::testComposeMaps(llvm::raw_ostream &outs) {
   maps.reserve(matches.size());
   for (auto m : llvm::reverse(matches)) {
     auto *opInst = m.getMatchedOperation();
     auto map = opInst->getAttr(VectorizerTestPass::kTestAffineMapAttrName)
                    .cast<AffineMapAttr>()
                    .getValue();
     maps.push_back(map);
   }
+  if (maps.empty())
+    // Nothing to compose
+    return;
   AffineMap res;
   for (auto m : maps) {
     res = res ? res.compose(m) : m;
   }
   simplifyAffineMap(res).print(outs << "\nComposed map: ");
 }
 
 /// Test for 'vectorizeAffineLoopNest' utility.