[AIG][LongestPathAnalysis] Fix a bug in deduplicatePathsImpl (#8746)

This commit fixes a bug in deduplicatePathsImpl within the AIG LongestPathAnalysis.

Close https://github.com/llvm/circt/issues/8745

integration_test/Bindings/Python/dialects/aig.py

@@ -41,7 +41,7 @@ with Context() as ctx, Location.unknown():
     # CHECK-LABEL:      LongestPathAnalysis created successfully!
     print("LongestPathAnalysis created successfully!")
 
-    # CHECK:      Total paths: 96
+    # CHECK:      Total paths: 128
     # CHECK-NEXT: Max delay: 2
     # CHECK-NEXT: Min delay: 1
     # CHECK-NEXT: 50th percentile delay: 1
@@ -62,17 +62,17 @@ with Context() as ctx, Location.unknown():
         DataflowPath.from_json_string(
             collection.collection.get_path(5)) == collection[5])
     # Check that len and get_size are the same
-    # CHECK-NEXT: 96 96
+    # CHECK-NEXT: 128 128
     print(len(collection), collection.collection.get_size())
 
     try:
-      print(collection[96])
+      print(collection[128])
     except IndexError:
       # CHECK-NEXT: IndexError correctly raised
       print("IndexError correctly raised")
 
     # Check that iterator works
-    # CHECK-NEXT: sum: 128
+    # CHECK-NEXT: sum: 192
     print("sum: ", sum(p.delay for p in collection))
 
     for p in collection[:2]:

lib/Dialect/AIG/Analysis/LongestPathAnalysis.cpp

@@ -87,19 +87,24 @@ deduplicatePathsImpl(SmallVectorImpl<T> &results, size_t startIndex,
                      llvm::function_ref<Key(const T &)> keyFn,
                      llvm::function_ref<int64_t(const T &)> delayFn) {
   // Take only maximum for each path destination.
-  DenseMap<Key, size_t> saved;
-  for (auto [i, path] :
-       llvm::enumerate(ArrayRef(results).drop_front(startIndex))) {
-    auto &slot = saved[keyFn(path)];
-    if (slot == 0) {
-      slot = startIndex + i + 1;
+  DenseMap<Key, size_t> keyToIndex;
+  for (size_t i = startIndex; i < results.size(); ++i) {
+    auto &path = results[i];
+    auto key = keyFn(path);
+    auto delay = delayFn(path);
+    auto it = keyToIndex.find(key);
+    if (it == keyToIndex.end()) {
+      // Insert a new entry.
+      size_t newIndex = keyToIndex.size() + startIndex;
+      keyToIndex[key] = newIndex;
+      results[newIndex] = std::move(results[i]);
       continue;
     }
-    if (delayFn(results[slot - 1]) < delayFn(path))
-      results[slot - 1] = path;
+    if (delay > delayFn(results[it->second]))
+      results[it->second] = std::move(results[i]);
   }
 
-  results.resize(saved.size() + startIndex);
+  results.resize(keyToIndex.size() + startIndex);
 }
 
 static void deduplicatePaths(SmallVectorImpl<OpenPath> &results,

test/Dialect/AIG/longest-paths.mlir

@@ -103,3 +103,10 @@ hw.module private @comb(in %cond : i1, in %a : i1, in %b : i1, out x : i1) {
   %r = comb.mux %cond, %a, %b : i1
   hw.output %r : i1
 }
+
+// expected-remark-re @below {{fanOut=Object($root.x[0]), fanIn=Object($root.a[0], delay=2, history=[{{.+}}])}}
+// expected-remark-re @below {{fanOut=Object($root.x[0]), fanIn=Object($root.b[0], delay=2, history=[{{.+}}])}}
+hw.module private @fix_duplication(in %a : i1, in %b : i1, out x : i1) {
+  %0 = aig.and_inv %a, %a, %b : i1
+  hw.output %0 : i1
+}

test/circt-synth/path-e2e.mlir

@@ -2,7 +2,7 @@
 // RUN: circt-synth %s -output-longest-path=- -top counter -output-longest-path-json | FileCheck %s --check-prefix JSON
 
 // CHECK-LABEL: # Longest Path Analysis result for "counter"
-// CHECK-NEXT: Found 189 paths
+// CHECK-NEXT: Found 288 paths
 // CHECK-NEXT: Found 32 unique fanout points
 // CHECK-NEXT: Maximum path delay: 48
 // Don't test detailed reports as they are not stable.