[wasm] Allow --trace-liftoff without --trace-wasm-decoder

There is not really a reason to guard the first by the latter. Just emit
a hint if --trace-liftoff is used without --trace-wasm-decoder, but
still make it work.
Also, used DEFINE_DEBUG_BOOL instead of guarding the output by another
"#ifdef DEBUG".

R=ahaas@chromium.org

Change-Id: Ia7d3f504df92779447877612e98b9c2a847b9f6b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2011828Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65894}

src/flags/flag-definitions.h

@@ -699,8 +699,8 @@ DEFINE_BOOL(liftoff, false,
             "enable Liftoff, the baseline compiler for WebAssembly")
 DEFINE_IMPLICATION(future, liftoff)
 #endif
-DEFINE_BOOL(trace_liftoff, false,
-            "trace Liftoff, the baseline compiler for WebAssembly")
+DEFINE_DEBUG_BOOL(trace_liftoff, false,
+                  "trace Liftoff, the baseline compiler for WebAssembly")
 DEFINE_BOOL(trace_wasm_memory, false,
             "print all memory updates performed in wasm code")
 // Fuzzers use {wasm_tier_mask_for_testing} together with {liftoff} and

src/wasm/baseline/liftoff-compiler.cc

@@ -388,6 +388,10 @@ class LiftoffCompiler {
   }
 
   void StartFunction(FullDecoder* decoder) {
+    if (FLAG_trace_liftoff && !FLAG_trace_wasm_decoder) {
+      StdoutStream{} << "hint: add --trace-wasm-decoder to also see the wasm "
+                        "instructions being decoded\n";
+    }
     int num_locals = decoder->num_locals();
     __ set_num_locals(num_locals);
     for (int i = 0; i < num_locals; ++i) {
@@ -2368,8 +2372,7 @@ class LiftoffCompiler {
   }
 
   void TraceCacheState(FullDecoder* decoder) const {
-#ifdef DEBUG
-    if (!FLAG_trace_liftoff || !FLAG_trace_wasm_decoder) return;
+    if (!FLAG_trace_liftoff) return;
     StdoutStream os;
     for (int control_depth = decoder->control_depth() - 1; control_depth >= -1;
          --control_depth) {
@@ -2381,7 +2384,6 @@ class LiftoffCompiler {
       if (control_depth != -1) PrintF("; ");
     }
     os << "\n";
-#endif
   }
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(LiftoffCompiler);