[liftoff] Use LiftoffRegList::MaskOut more consistently

The {MaskOut} operation is faster than using {operator~}, since
{operator~} needs to ensure to return a valid register list, so it
contains an additional AND operation with the mask of all registers.
Hence use {MaskOut} more consistently, and remove the now unused
{operator~} on {LiftoffRegList}.

R=ahaas@chromium.org

Bug: v8:6600
Change-Id: Icf072e564c4e391cafa2abeeba53cf275cee75f8
Reviewed-on: https://chromium-review.googlesource.com/c/1275810Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56560}

src/wasm/baseline/liftoff-assembler.h

@@ -127,7 +127,7 @@ class LiftoffAssembler : public TurboAssembler {
     bool has_unused_register(RegClass rc, LiftoffRegList pinned = {}) const {
       if (kNeedI64RegPair && rc == kGpRegPair) {
         LiftoffRegList available_regs =
-            kGpCacheRegList & ~used_registers & ~pinned;
+            kGpCacheRegList.MaskOut(used_registers).MaskOut(pinned);
         return available_regs.GetNumRegsSet() >= 2;
       }
       DCHECK(rc == kGpReg || rc == kFpReg);
@@ -137,7 +137,8 @@ class LiftoffAssembler : public TurboAssembler {
 
     bool has_unused_register(LiftoffRegList candidates,
                              LiftoffRegList pinned = {}) const {
-      LiftoffRegList available_regs = candidates & ~used_registers & ~pinned;
+      LiftoffRegList available_regs =
+          candidates.MaskOut(used_registers).MaskOut(pinned);
       return !available_regs.is_empty();
     }
 
@@ -155,7 +156,8 @@ class LiftoffAssembler : public TurboAssembler {
 
     LiftoffRegister unused_register(LiftoffRegList candidates,
                                     LiftoffRegList pinned = {}) const {
-      LiftoffRegList available_regs = candidates & ~used_registers & ~pinned;
+      LiftoffRegList available_regs =
+          candidates.MaskOut(used_registers).MaskOut(pinned);
       return available_regs.GetFirstRegSet();
     }
 

src/wasm/baseline/liftoff-register.h

@@ -253,10 +253,6 @@ class LiftoffRegList {
     return LiftoffRegList(regs_ & other.regs_);
   }
 
-  constexpr LiftoffRegList operator~() const {
-    return LiftoffRegList(~regs_ & (kGpMask | kFpMask));
-  }
-
   constexpr bool operator==(const LiftoffRegList other) const {
     return regs_ == other.regs_;
   }