[Liftoff] Compile validation method only for SLOW_DCHECK

This method is only used in a slow dcheck, thus omit it completely
otherwise.

R=ahaas@chromium.org

Bug: v8:8238
Change-Id: Ic23d0ff10a1dfe9f383237c99a365c2d3ee93e51
Reviewed-on: https://chromium-review.googlesource.com/c/1349233Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57781}

src/wasm/baseline/liftoff-assembler.cc

@@ -604,6 +604,7 @@ void LiftoffAssembler::ParallelRegisterMove(
   }
 }
 
+#ifdef ENABLE_SLOW_DCHECKS
 bool LiftoffAssembler::ValidateCacheState() const {
   uint32_t register_use_count[kAfterMaxLiftoffRegCode] = {0};
   LiftoffRegList used_regs;
@@ -631,6 +632,7 @@ bool LiftoffAssembler::ValidateCacheState() const {
   os << "Use --trace-liftoff to debug.";
   FATAL("%s", os.str().c_str());
 }
+#endif
 
 LiftoffRegister LiftoffAssembler::SpillOneRegister(LiftoffRegList candidates,
                                                    LiftoffRegList pinned) {

src/wasm/baseline/liftoff-assembler.h

@@ -338,8 +338,10 @@ class LiftoffAssembler : public TurboAssembler {
   };
   void ParallelRegisterMove(Vector<ParallelRegisterMoveTuple>);
 
+#ifdef ENABLE_SLOW_DCHECKS
   // Validate that the register use counts reflect the state of the cache.
   bool ValidateCacheState() const;
+#endif
 
   ////////////////////////////////////
   // Platform-specific part.        //