[regexp] Simplify allocation of RegExpMacroAssemblerTracer

This change is motivated by SpiderMonkey's policy against bare
new/delete. (I also think it's just a nicer way to write this.)

R=jgruber@chromium.org

here is the same as the change I made in the equivalent SM code.

Note: I'm not importing regexp.cc into SpiderMonkey, but the change
Bug: v8:10303
Change-Id: I3c81727eb7dea9c0ec78241e3c82ffc9e7007827
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2091858
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66713}

src/regexp/regexp-compiler.cc

@@ -8,7 +8,6 @@
 #include "src/execution/isolate.h"
 #include "src/objects/objects-inl.h"
 #include "src/regexp/regexp-macro-assembler-arch.h"
-#include "src/regexp/regexp-macro-assembler-tracer.h"
 #ifdef V8_INTL_SUPPORT
 #include "src/regexp/special-case.h"
 #endif  // V8_INTL_SUPPORT
@@ -245,12 +244,7 @@ RegExpCompiler::RegExpCompiler(Isolate* isolate, Zone* zone, int capture_count,
 RegExpCompiler::CompilationResult RegExpCompiler::Assemble(
     Isolate* isolate, RegExpMacroAssembler* macro_assembler, RegExpNode* start,
     int capture_count, Handle<String> pattern) {
-#ifdef DEBUG
-  if (FLAG_trace_regexp_assembler)
-    macro_assembler_ = new RegExpMacroAssemblerTracer(isolate, macro_assembler);
-  else
-#endif
-    macro_assembler_ = macro_assembler;
+  macro_assembler_ = macro_assembler;
 
   ZoneVector<RegExpNode*> work_list(zone());
   work_list_ = &work_list;
@@ -275,11 +269,6 @@ RegExpCompiler::CompilationResult RegExpCompiler::Assemble(
   isolate->IncreaseTotalRegexpCodeGenerated(code);
   work_list_ = nullptr;
 
-#ifdef DEBUG
-  if (FLAG_trace_regexp_assembler) {
-    delete macro_assembler_;
-  }
-#endif
   return {*code, next_register_};
 }
 

src/regexp/regexp.cc

@@ -14,6 +14,7 @@
 #include "src/regexp/regexp-dotprinter.h"
 #include "src/regexp/regexp-interpreter.h"
 #include "src/regexp/regexp-macro-assembler-arch.h"
+#include "src/regexp/regexp-macro-assembler-tracer.h"
 #include "src/regexp/regexp-parser.h"
 #include "src/strings/string-search.h"
 #include "src/utils/ostreams.h"
@@ -878,8 +879,18 @@ bool RegExpImpl::Compile(Isolate* isolate, Zone* zone, RegExpCompileData* data,
     macro_assembler->set_global_mode(mode);
   }
 
+  RegExpMacroAssembler* macro_assembler_ptr = macro_assembler.get();
+#ifdef DEBUG
+  std::unique_ptr<RegExpMacroAssembler> tracer_macro_assembler;
+  if (FLAG_trace_regexp_assembler) {
+    tracer_macro_assembler.reset(
+        new RegExpMacroAssemblerTracer(isolate, macro_assembler_ptr));
+    macro_assembler_ptr = tracer_macro_assembler.get();
+  }
+#endif
+
   RegExpCompiler::CompilationResult result = compiler.Assemble(
-      isolate, macro_assembler.get(), node, data->capture_count, pattern);
+      isolate, macro_assembler_ptr, node, data->capture_count, pattern);
 
   // Code / bytecode printing.
   {