[arm64] Remove unnecessary calls to CPURegList::IsValid

In the mjsunit/wasm/asm-wasm-f32 test, {IsValid} caused 10% of the
overall runtime. In absolute numbers, {IsValid} wasm called more
than 6.000.000.000 times. I moved the calls to {IsValid} from
before-use to after-modification. I removed the calls in {Combine}
and {Remove}, because these operations cannot create an invalid
CPURegList.
These changes reduce the number of calls to {IsValid} to about
100.000.000 in the test mentioned above, and saves for that test
about 10 seconds out of before 2 minutes absolute runtime.

R=v8-arm-port@googlegroups.com

Bug: v8:9396
Change-Id: If3059f471e423405ec6f34ddef89e314dee1cbaf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1801851
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Martyn Capewell <martyn.capewell@arm.com>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63864}

src/codegen/arm64/assembler-arm64-inl.h

@@ -54,14 +54,12 @@ inline bool CPURegister::IsSP() const {
 }
 
 inline void CPURegList::Combine(const CPURegList& other) {
-  DCHECK(IsValid());
   DCHECK(other.type() == type_);
   DCHECK(other.RegisterSizeInBits() == size_);
   list_ |= other.list();
 }
 
 inline void CPURegList::Remove(const CPURegList& other) {
-  DCHECK(IsValid());
   if (other.type() == type_) {
     list_ &= ~other.list();
   }
@@ -84,13 +82,12 @@ inline void CPURegList::Remove(const CPURegister& other1,
 }
 
 inline void CPURegList::Combine(int code) {
-  DCHECK(IsValid());
   DCHECK(CPURegister::Create(code, size_, type_).IsValid());
   list_ |= (1ULL << code);
+  DCHECK(IsValid());
 }
 
 inline void CPURegList::Remove(int code) {
-  DCHECK(IsValid());
   DCHECK(CPURegister::Create(code, size_, type_).IsValid());
   list_ &= ~(1ULL << code);
 }

src/codegen/arm64/assembler-arm64.cc

@@ -63,7 +63,6 @@ void CpuFeatures::PrintFeatures() {}
 // CPURegList utilities.
 
 CPURegister CPURegList::PopLowestIndex() {
-  DCHECK(IsValid());
   if (IsEmpty()) {
     return NoCPUReg;
   }
@@ -74,7 +73,6 @@ CPURegister CPURegList::PopLowestIndex() {
 }
 
 CPURegister CPURegList::PopHighestIndex() {
-  DCHECK(IsValid());
   if (IsEmpty()) {
     return NoCPUReg;
   }

src/codegen/arm64/register-arm64.h

@@ -595,18 +595,16 @@ class V8_EXPORT_PRIVATE CPURegList {
   }
 
   CPURegister::RegisterType type() const {
-    DCHECK(IsValid());
     return type_;
   }
 
   RegList list() const {
-    DCHECK(IsValid());
     return list_;
   }
 
   inline void set_list(RegList new_list) {
-    DCHECK(IsValid());
     list_ = new_list;
+    DCHECK(IsValid());
   }
 
   // Combine another CPURegList into this one. Registers that already exist in
@@ -654,7 +652,6 @@ class V8_EXPORT_PRIVATE CPURegList {
   static CPURegList GetSafepointSavedRegisters();
 
   bool IsEmpty() const {
-    DCHECK(IsValid());
     return list_ == 0;
   }
 
@@ -662,7 +659,6 @@ class V8_EXPORT_PRIVATE CPURegList {
                        const CPURegister& other2 = NoCPUReg,
                        const CPURegister& other3 = NoCPUReg,
                        const CPURegister& other4 = NoCPUReg) const {
-    DCHECK(IsValid());
     RegList list = 0;
     if (!other1.IsNone() && (other1.type() == type_)) list |= other1.bit();
     if (!other2.IsNone() && (other2.type() == type_)) list |= other2.bit();
@@ -672,12 +668,10 @@ class V8_EXPORT_PRIVATE CPURegList {
   }
 
   int Count() const {
-    DCHECK(IsValid());
     return CountSetBits(list_, kRegListSizeInBits);
   }
 
   int RegisterSizeInBits() const {
-    DCHECK(IsValid());
     return size_;
   }
 
@@ -688,7 +682,6 @@ class V8_EXPORT_PRIVATE CPURegList {
   }
 
   int TotalSizeInBytes() const {
-    DCHECK(IsValid());
     return RegisterSizeInBytes() * Count();
   }