src/hotspot/cpu/aarch64/register_aarch64.hpp

rev 60623 : 8248500: AArch64: Remove the r18 dependency on Windows AArch64
Reviewed-by:
Contributed-by: mbeckwit, luhenry, burban

*** 89,99 ****
  CONSTANT_REGISTER_DECLARATION(Register, r13,  (13));
  CONSTANT_REGISTER_DECLARATION(Register, r14,  (14));
  CONSTANT_REGISTER_DECLARATION(Register, r15,  (15));
  CONSTANT_REGISTER_DECLARATION(Register, r16,  (16));
  CONSTANT_REGISTER_DECLARATION(Register, r17,  (17));
! CONSTANT_REGISTER_DECLARATION(Register, r18,  (18));
  CONSTANT_REGISTER_DECLARATION(Register, r19,  (19));
  CONSTANT_REGISTER_DECLARATION(Register, r20,  (20));
  CONSTANT_REGISTER_DECLARATION(Register, r21,  (21));
  CONSTANT_REGISTER_DECLARATION(Register, r22,  (22));
  CONSTANT_REGISTER_DECLARATION(Register, r23,  (23));
--- 89,110 ----
  CONSTANT_REGISTER_DECLARATION(Register, r13,  (13));
  CONSTANT_REGISTER_DECLARATION(Register, r14,  (14));
  CONSTANT_REGISTER_DECLARATION(Register, r15,  (15));
  CONSTANT_REGISTER_DECLARATION(Register, r16,  (16));
  CONSTANT_REGISTER_DECLARATION(Register, r17,  (17));
! 
! // In the ABI for Windows+AArch64 the register r18 is used to store the pointer
! // to the current thread's TEB (where TLS variables are stored). We could
! // carefully save and restore r18 at key places, however Win32 Structured
! // Exception Handling (SEH) is using TLS to unwind the stack. If r18 is used
! // for any other purpose at the time of an exception happening, SEH would not
! // be able to unwind the stack properly and most likely crash.
! //
! // It's easier to avoid allocating r18 altogether.
! //
! // See https://docs.microsoft.com/en-us/cpp/build/arm64-windows-abi-conventions?view=vs-2019#integer-registers
! CONSTANT_REGISTER_DECLARATION(Register, r18_tls,  (18));
  CONSTANT_REGISTER_DECLARATION(Register, r19,  (19));
  CONSTANT_REGISTER_DECLARATION(Register, r20,  (20));
  CONSTANT_REGISTER_DECLARATION(Register, r21,  (21));
  CONSTANT_REGISTER_DECLARATION(Register, r22,  (22));
  CONSTANT_REGISTER_DECLARATION(Register, r23,  (23));
*** 205,214 ****
--- 216,227 ----
    // added to make it compile
    static const int max_gpr;
    static const int max_fpr;
  };
  
+ class RegSetIterator;
+ 
  // A set of registers
  class RegSet {
    uint32_t _bitset;
  
    RegSet(uint32_t bitset) : _bitset(bitset) { }
*** 263,270 ****
--- 276,326 ----
  
      return RegSet(bits);
    }
  
    uint32_t bits() const { return _bitset; }
+ 
+ private:
+ 
+   Register first() {
+     uint32_t first = _bitset & -_bitset;
+     return first ? as_Register(exact_log2(first)) : noreg;
+   }
+ 
+ public:
+ 
+   friend class RegSetIterator;
+ 
+   RegSetIterator begin();
  };
  
+ class RegSetIterator {
+   RegSet _regs;
+ 
+ public:
+   RegSetIterator(RegSet x): _regs(x) {}
+   RegSetIterator(const RegSetIterator& mit) : _regs(mit._regs) {}
+ 
+   RegSetIterator& operator++() {
+     Register r = _regs.first();
+     if (r != noreg)
+       _regs -= r;
+     return *this;
+   }
+ 
+   bool operator==(const RegSetIterator& rhs) const {
+     return _regs.bits() == rhs._regs.bits();
+   }
+   bool operator!=(const RegSetIterator& rhs) const {
+     return ! (rhs == *this);
+   }
+ 
+   Register operator*() {
+     return _regs.first();
+   }
+ };
+ 
+ inline RegSetIterator RegSet::begin() {
+   return RegSetIterator(*this);
+ }
+ 
  #endif // CPU_AARCH64_REGISTER_AARCH64_HPP