8349814: [leyden] Reduce uncommon traps in preload code

src/hotspot/share/compiler/compiler_globals.hpp

@@ -491,6 +491,9 @@
   product(bool, PrecompileOnlyAndExit, false,                               \
           "Exit after precompilation step is over")                         \
                                                                             \
+  product(bool, PreloadReduceTraps, true, DIAGNOSTIC,                       \
+          "Preload code should avoid traps as much as possible.")           \
+                                                                            \
   product(bool, PreloadBlocking, false, DIAGNOSTIC,                         \
           "Preload code is processed with blocking. Startup would not "     \
           "proceed until all code preloaded code is done loading.")         \

src/hotspot/share/opto/compile.cpp

@@ -4052,6 +4052,10 @@ bool Compile::too_many_traps(ciMethod* method,
   if (method->has_trap_at(bci)) {
     return true;
   }
+  if (PreloadReduceTraps && for_preload()) {
+    // Preload code should not have traps, if possible.
+    return true;
+  }
   ciMethodData* md = method->method_data();
   if (md->is_empty()) {
     // Assume the trap has not occurred, or that it occurred only
@@ -4077,6 +4081,10 @@ bool Compile::too_many_traps(ciMethod* method,
 // Less-accurate variant which does not require a method and bci.
 bool Compile::too_many_traps(Deoptimization::DeoptReason reason,
                              ciMethodData* logmd) {
+  if (PreloadReduceTraps && for_preload()) {
+    // Preload code should not have traps, if possible.
+    return true;
+  }
   if (trap_count(reason) >= Deoptimization::per_method_trap_limit(reason)) {
     // Too many traps globally.
     // Note that we use cumulative trap_count, not just md->trap_count.

src/hotspot/share/opto/graphKit.cpp

@@ -2123,6 +2123,16 @@ Node* GraphKit::uncommon_trap(int trap_request,
                                                       trap_request), bci());
   }
 
+  if (PreloadReduceTraps && Compile::current()->for_preload() &&
+      (action != Deoptimization::Action_none)) {
+    ResourceMark rm;
+    ciMethod* cim = Compile::current()->method();
+    log_info(scc)("Uncommon trap in preload code: reason=%s action=%s method=%s::%s bci=%d",
+                  Deoptimization::trap_reason_name(reason), Deoptimization::trap_action_name(action),
+                  cim->holder()->name()->as_klass_external_name(), cim->name()->as_klass_external_name(),
+                  bci());
+  }
+
   CompileLog* log = C->log();
   if (log != nullptr) {
     int kid = (klass == nullptr)? -1: log->identify(klass);

src/hotspot/share/runtime/deoptimization.cpp

@@ -2126,6 +2126,14 @@ JRT_ENTRY_PROF(void, Deoptimization, uncommon_trap_inner, Deoptimization::uncomm
       Events::log_deopt_message(current, "Uncommon trap: reason=%s action=%s pc=" INTPTR_FORMAT " method=%s @ %d %s",
                                 reason_name, reason_action, pc,
                                 tm->name_and_sig_as_C_string(), trap_bci, nm->compiler_name());
+
+      if (PreloadReduceTraps && nm->preloaded() && (action != Action_none)) {
+        // For performance reasons, preloaded nmethods should avoid deopts that lead to recompilations.
+        // Compiler logs all uncommon traps with -Xlog:scc. That log is noisy, and some traps may be
+        // legitimate. Here, we log the problems that really caused the deopts at runtime.
+        log_warning(deoptimization)("In preload code: reason=%s action=%s method=%s",
+          reason_name, reason_action, tm->name_and_sig_as_C_string());
+      }
     }
 
     // Print a bunch of diagnostics, if requested.