[mlir] Fixed ordering of pass statistics.

[vzakhari]

Summary

The change makes sure the plain C string statistics names
are properly ordered.

[vzakhari]

The original code causes flaky failures like in D130035 (LIT testing failed on Windows and passed on Linux).

mlir/lib/Pass/PassStatistics.cpp

 /// Utility to print a pass entry in the statistics output.
 static void printPassEntry(raw_ostream &os, unsigned indent, StringRef pass,
                            MutableArrayRef<Statistic> stats = llvm::None) {
   os.indent(indent) << pass << "\n";
   if (stats.empty())
     return;
 
   // Make sure to sort the statistics by name.
-  llvm::array_pod_sort(stats.begin(), stats.end(),
-                       [](const auto *lhs, const auto *rhs) {
-                         return llvm::array_pod_sort_comparator<const char *>(
-                             &lhs->name, &rhs->name);
-                       });
+  llvm::array_pod_sort(
+      stats.begin(), stats.end(), [](const auto *lhs, const auto *rhs) {
+        return StringRef{lhs->name}.compare(StringRef{rhs->name});
 
   // Collect the largest name and value length from each of the statistics.
   size_t largestName = 0, largestValue = 0;
   for (auto &stat : stats) {
     largestName = std::max(largestName, (size_t)strlen(stat.name));
     largestValue =
         std::max(largestValue, (size_t)llvm::utostr(stat.value).size());
   }

mlir/test/Pass/pipeline-stats.mlir

 // REQUIRES: asserts
 // RUN: mlir-opt %s -verify-each=true -pass-pipeline='func.func(test-stats-pass,test-stats-pass)' -mlir-pass-statistics -mlir-pass-statistics-display=list 2>&1 | FileCheck -check-prefix=LIST %s
 // RUN: mlir-opt %s -verify-each=true -pass-pipeline='func.func(test-stats-pass,test-stats-pass)' -mlir-pass-statistics -mlir-pass-statistics-display=pipeline 2>&1 | FileCheck -check-prefix=PIPELINE %s
 
 // LIST: Pass statistics report
 // LIST: TestStatisticPass
 // LIST-NEXT:  (S) {{0|8}} num-ops - Number of operations counted
+// LIST-NEXT:  (S) {{0|8}} num-ops2 - Number of operations counted one more time
 // LIST-NOT: Verifier
 
 // PIPELINE: Pass statistics report
 // PIPELINE: 'func.func' Pipeline
 // PIPELINE-NEXT:   TestStatisticPass
 // PIPELINE-NEXT:     (S) {{0|4}} num-ops - Number of operations counted
+// PIPELINE-NEXT:     (S) {{0|4}} num-ops2 - Number of operations counted one more time
 // PIPELINE-NEXT:   TestStatisticPass
 // PIPELINE-NEXT:     (S) {{0|4}} num-ops - Number of operations counted
+// PIPELINE-NEXT:     (S) {{0|4}} num-ops2 - Number of operations counted one more time
 
 func.func @foo() {
   return
 }
 
 func.func @bar() {
   return
 }

mlir/test/lib/Pass/TestPassManager.cpp

struct TestStatisticPass
     : public PassWrapper<TestStatisticPass, OperationPass<>> {
   MLIR_DEFINE_EXPLICIT_INTERNAL_INLINE_TYPE_ID(TestStatisticPass)
 
   TestStatisticPass() = default;
   TestStatisticPass(const TestStatisticPass &) : PassWrapper() {}
   StringRef getArgument() const final { return "test-stats-pass"; }
   StringRef getDescription() const final { return "Test pass statistics"; }
 
+  // Use a couple of statistics to verify their ordering
+  // in the print out. The statistics are registered in the order
+  // of construction, so put "num-ops2" before "num-ops" and
+  // make sure that the order is reversed.
+  Statistic opCountDuplicate{this, "num-ops2",
+                             "Number of operations counted one more time"};
   Statistic opCount{this, "num-ops", "Number of operations counted"};
 
   void runOnOperation() final {
     getOperation()->walk([&](Operation *) { ++opCount; });
+    getOperation()->walk([&](Operation *) { ++opCountDuplicate; });
   }
 };
 } // namespace
 
 static void testNestedPipeline(OpPassManager &pm) {
   // Nest a module pipeline that contains:
   /// A module pass.
   auto &modulePM = pm.nest<ModuleOp>();