[turbofan] Do not unroll loops with function calls

Spending time on unrolling loops that contain function calls will often
not be worth it, as these loops will run for potentially a long time,
mitigating the performance benefit of loop unrolling.

Bug: v8:11298, v8:12047
Change-Id: Idd59cea499e495e90c48f82133a809b22f899d74
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3081614
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76203}

src/compiler/loop-analysis.cc

@@ -543,8 +543,9 @@ LoopTree* LoopFinder::BuildLoopTree(Graph* graph, TickCounter* tick_counter,
   return loop_tree;
 }
 
+#if V8_ENABLE_WEBASSEMBLY
 // static
-ZoneUnorderedSet<Node*>* LoopFinder::FindUnnestedLoopFromHeader(
+ZoneUnorderedSet<Node*>* LoopFinder::FindSmallUnnestedLoopFromHeader(
     Node* loop_header, Zone* zone, size_t max_size) {
   auto* visited = zone->New<ZoneUnorderedSet<Node*>>(zone);
   std::vector<Node*> queue;
@@ -580,6 +581,12 @@ ZoneUnorderedSet<Node*>* LoopFinder::FindUnnestedLoopFromHeader(
                   loop_header);
         // All uses are outside the loop, do nothing.
         break;
+      case IrOpcode::kCall:
+      case IrOpcode::kTailCall:
+      case IrOpcode::kJSWasmCall:
+      case IrOpcode::kJSCall:
+        // Call nodes are considered to have unbounded size, i.e. >max_size.
+        return nullptr;
       default:
         for (Node* use : node->uses()) {
           if (visited->count(use) == 0) queue.push_back(use);
@@ -614,6 +621,7 @@ ZoneUnorderedSet<Node*>* LoopFinder::FindUnnestedLoopFromHeader(
 
   return visited;
 }
+#endif  // V8_ENABLE_WEBASSEMBLY
 
 bool LoopFinder::HasMarkedExits(LoopTree* loop_tree,
                                 const LoopTree::Loop* loop) {

src/compiler/loop-analysis.h

@@ -179,16 +179,19 @@ class V8_EXPORT_PRIVATE LoopFinder {
 
   static bool HasMarkedExits(LoopTree* loop_tree_, const LoopTree::Loop* loop);
 
-  // Find all nodes of a loop given its header node. Will exit early once the
-  // current loop size exceed {max_size}. This is a very restricted version of
-  // BuildLoopTree.
-  // Assumptions:
+#if V8_ENABLE_WEBASSEMBLY
+  // Find all nodes of a loop given headed by {loop_header}. Returns {nullptr}
+  // if the loop size in Nodes exceeds {max_size}. In that context, function
+  // calls are considered to have unbounded size, so if the loop contains a
+  // function call, {nullptr} is always returned.
+  // This is a very restricted version of BuildLoopTree and makes the following
+  // assumptions:
   // 1) All loop exits of the loop are marked with LoopExit, LoopExitEffect,
   //    and LoopExitValue nodes.
   // 2) There are no nested loops within this loop.
-  static ZoneUnorderedSet<Node*>* FindUnnestedLoopFromHeader(Node* loop_header,
-                                                             Zone* zone,
-                                                             size_t max_size);
+  static ZoneUnorderedSet<Node*>* FindSmallUnnestedLoopFromHeader(
+      Node* loop_header, Zone* zone, size_t max_size);
+#endif
 };
 
 // Copies a range of nodes any number of times.

src/compiler/pipeline.cc

@@ -1672,11 +1672,12 @@ struct WasmLoopUnrollingPhase {
            std::vector<compiler::WasmLoopInfo>* loop_infos) {
     for (WasmLoopInfo& loop_info : *loop_infos) {
       if (loop_info.is_innermost) {
-        ZoneUnorderedSet<Node*>* loop = LoopFinder::FindUnnestedLoopFromHeader(
-            loop_info.header, temp_zone,
-            // Only discover the loop until its size is the maximum unrolled
-            // size for its depth.
-            maximum_unrollable_size(loop_info.nesting_depth));
+        ZoneUnorderedSet<Node*>* loop =
+            LoopFinder::FindSmallUnnestedLoopFromHeader(
+                loop_info.header, temp_zone,
+                // Only discover the loop until its size is the maximum unrolled
+                // size for its depth.
+                maximum_unrollable_size(loop_info.nesting_depth));
         UnrollLoop(loop_info.header, loop, loop_info.nesting_depth,
                    data->graph(), data->common(), temp_zone,
                    data->source_positions(), data->node_origins());