[cleanup] Ignore no_regs in AreAliased()

in order to make it also work with optional registers.

Bug: v8:8562
Change-Id: Iaea905913cc9fd1637026b83e9356c740965e128
Reviewed-on: https://chromium-review.googlesource.com/c/1367807
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58105}

src/assembler.h

@@ -475,9 +475,14 @@ class RegisterBase {
     return static_cast<int>(reg_code);
   }
 
+  template <RegisterCode reg_code>
+  static constexpr int is_valid() {
+    return static_cast<int>(reg_code) != kCode_no_reg;
+  }
+
   template <RegisterCode reg_code>
   static constexpr RegList bit() {
-    return RegList{1} << code<reg_code>();
+    return is_valid<reg_code>() ? RegList{1} << code<reg_code>() : RegList{};
   }
 
   static SubType from_code(int code) {
@@ -498,14 +503,14 @@ class RegisterBase {
     return CombineRegLists(regs.bit()...);
   }
 
-  bool is_valid() const { return reg_code_ != kCode_no_reg; }
+  constexpr bool is_valid() const { return reg_code_ != kCode_no_reg; }
 
   int code() const {
     DCHECK(is_valid());
     return reg_code_;
   }
 
-  RegList bit() const { return RegList{1} << code(); }
+  RegList bit() const { return is_valid() ? RegList{1} << code() : RegList{}; }
 
   inline constexpr bool operator==(SubType other) const {
     return reg_code_ == other.reg_code_;

src/turbo-assembler.h

@@ -131,6 +131,13 @@ class HardAbortScope {
 enum class StubCallMode { kCallOnHeapBuiltin, kCallWasmRuntimeStub };
 
 #ifdef DEBUG
+struct CountIfValidRegisterFunctor {
+  template <typename RegType>
+  constexpr int operator()(int count, RegType reg) const {
+    return count + (reg.is_valid() ? 1 : 0);
+  }
+};
+
 template <typename RegType, typename... RegTypes,
           // All arguments must be either Register or DoubleRegister.
           typename = typename std::enable_if<
@@ -138,7 +145,8 @@ template <typename RegType, typename... RegTypes,
               base::is_same<DoubleRegister, RegType, RegTypes...>::value>::type>
 inline bool AreAliased(RegType first_reg, RegTypes... regs) {
   int num_different_regs = NumRegs(RegType::ListOf(first_reg, regs...));
-  int num_given_regs = sizeof...(regs) + 1;
+  int num_given_regs =
+      base::fold(CountIfValidRegisterFunctor{}, 0, first_reg, regs...);
   return num_different_regs < num_given_regs;
 }
 #endif

test/cctest/test-macro-assembler-x64.cc

@@ -1114,6 +1114,22 @@ TEST(SIMDMacros) {
   CHECK_EQ(0, result);
 }
 
+TEST(AreAliased) {
+  DCHECK(!AreAliased(rax));
+  DCHECK(!AreAliased(rax, no_reg));
+  DCHECK(!AreAliased(no_reg, rax, no_reg));
+
+  DCHECK(AreAliased(rax, rax));
+  DCHECK(!AreAliased(no_reg, no_reg));
+
+  DCHECK(!AreAliased(rax, rbx, rcx, rdx, no_reg));
+  DCHECK(AreAliased(rax, rbx, rcx, rdx, rax, no_reg));
+
+  // no_regs are allowed in
+  DCHECK(!AreAliased(rax, no_reg, rbx, no_reg, rcx, no_reg, rdx, no_reg));
+  DCHECK(AreAliased(rax, no_reg, rbx, no_reg, rcx, no_reg, rdx, rax, no_reg));
+}
+
 #undef __
 
 }  // namespace test_macro_assembler_x64