[libunwind] Express Registers_*::lastDwarfReg using _LIBUNWIND_HIGHEST_DWARF_REGISTER

[mstorsjo]

Summary

This avoids having to keep the same information duplicated in multiple places.

Adjust _LIBUNWIND_HIGHEST_DWARF_REGISTER to actually have the value of the highest used register and only use the value _LIBUNWIND_HIGHEST_DWARF_REGISTER + 1 (kMaxRegisterNumber + 1) for allocating the savedRegisters array.

[bsdjhb]

I think one source of truth is better than two. I do find the constant's value a bit off in general though. That is, the name 'HIGHEST' implies to me that it is the highest value used, not N + 1 as we currently define it.

[mstorsjo]

Adjusted _LIBUNWIND_HIGHEST_DWARF_REGISTER to actually have the value of the highest register, not highest+1.

[compnerd]

src/DwarfInstructions.hpp

170 ↗

(On Diff #120467)

Please use static_cast rather than the C style cast.

libunwind/trunk/include/__libunwind_config.h

 #define _LIBUNWIND_ARM_EHABI
 #endif
 
 #if defined(_LIBUNWIND_IS_NATIVE_ONLY)
 # if defined(__i386__)
 #  define _LIBUNWIND_TARGET_I386
 #  define _LIBUNWIND_CONTEXT_SIZE 8
 #  define _LIBUNWIND_CURSOR_SIZE 19
-#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 9
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 8
 # elif defined(__x86_64__)
 #  define _LIBUNWIND_TARGET_X86_64 1
 #  define _LIBUNWIND_CONTEXT_SIZE 21
 #  define _LIBUNWIND_CURSOR_SIZE 33
-#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 17
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 16
 # elif defined(__ppc__)
 #  define _LIBUNWIND_TARGET_PPC 1
 #  define _LIBUNWIND_CONTEXT_SIZE 117
 #  define _LIBUNWIND_CURSOR_SIZE 128
-#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 113
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 112
 # elif defined(__aarch64__)
 #  define _LIBUNWIND_TARGET_AARCH64 1
 #  define _LIBUNWIND_CONTEXT_SIZE 66
 #  define _LIBUNWIND_CURSOR_SIZE 78
-#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 96
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 95
 # elif defined(__arm__)
 #  define _LIBUNWIND_TARGET_ARM 1
 #  if defined(__ARM_WMMX)
 #    define _LIBUNWIND_CONTEXT_SIZE 61
 #    define _LIBUNWIND_CURSOR_SIZE 68
 #  else
 #    define _LIBUNWIND_CONTEXT_SIZE 42
 #    define _LIBUNWIND_CURSOR_SIZE 49
 #  endif
-#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 96
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 95
 # elif defined(__or1k__)
 #  define _LIBUNWIND_TARGET_OR1K 1
 #  define _LIBUNWIND_CONTEXT_SIZE 16
 #  define _LIBUNWIND_CURSOR_SIZE 28
-#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 32
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 31
 # else
 #  error "Unsupported architecture."
 # endif
 #else // !_LIBUNWIND_IS_NATIVE_ONLY
 # define _LIBUNWIND_TARGET_I386
 # define _LIBUNWIND_TARGET_X86_64 1
 # define _LIBUNWIND_TARGET_PPC 1
 # define _LIBUNWIND_TARGET_AARCH64 1
 # define _LIBUNWIND_TARGET_ARM 1
 # define _LIBUNWIND_TARGET_OR1K 1
 # define _LIBUNWIND_CONTEXT_SIZE 128
 # define _LIBUNWIND_CURSOR_SIZE 140
-# define _LIBUNWIND_HIGHEST_DWARF_REGISTER 120
+# define _LIBUNWIND_HIGHEST_DWARF_REGISTER 119
 #endif // _LIBUNWIND_IS_NATIVE_ONLY
 
 #endif // ____LIBUNWIND_CONFIG_H__

libunwind/trunk/src/DwarfInstructions.hpp

if (CFI_Parser<A>::parseFDEInstructions(addressSpace, fdeInfo, cieInfo, pc,
                                             &prolog)) {
       // get pointer to cfa (architecture specific)
       pint_t cfa = getCFA(addressSpace, prolog, registers);
 
        // restore registers that DWARF says were saved
       R newRegisters = registers;
       pint_t returnAddress = 0;
       const int lastReg = R::lastDwarfRegNum();
-      assert((int)CFI_Parser<A>::kMaxRegisterNumber > lastReg &&
+      assert(static_cast<int>(CFI_Parser<A>::kMaxRegisterNumber) >= lastReg &&
              "register range too large");
       assert(lastReg >= (int)cieInfo.returnAddressRegister &&
              "register range does not contain return address register");
       for (int i = 0; i <= lastReg; ++i) {
         if (prolog.savedRegisters[i].location !=
             CFI_Parser<A>::kRegisterUnused) {
           if (registers.validFloatRegister(i))
             newRegisters.setFloatRegister(

libunwind/trunk/src/DwarfParser.hpp

public:
   struct PrologInfo {
     uint32_t          cfaRegister;
     int32_t           cfaRegisterOffset;  // CFA = (cfaRegister)+cfaRegisterOffset
     int64_t           cfaExpression;      // CFA = expression
     uint32_t          spExtraArgSize;
     uint32_t          codeOffsetAtStackDecrement;
     bool              registersInOtherRegisters;
     bool              sameValueUsed;
-    RegisterLocation  savedRegisters[kMaxRegisterNumber];
+    RegisterLocation  savedRegisters[kMaxRegisterNumber + 1];
   };
 
   struct PrologInfoStackEntry {
     PrologInfoStackEntry(PrologInfoStackEntry *n, const PrologInfo &i)
         : next(n), info(i) {}
     PrologInfoStackEntry *next;
     PrologInfo info;
   };

libunwind/trunk/src/Registers.hpp

public:
   bool        validFloatRegister(int) const { return false; }
   double      getFloatRegister(int num) const;
   void        setFloatRegister(int num, double value);
   bool        validVectorRegister(int) const { return false; }
   v128        getVectorRegister(int num) const;
   void        setVectorRegister(int num, v128 value);
   const char *getRegisterName(int num);
   void        jumpto();
-  static int  lastDwarfRegNum() { return 8; }
+  static int  lastDwarfRegNum() { return _LIBUNWIND_HIGHEST_DWARF_REGISTER; }
 
   uint32_t  getSP() const          { return _registers.__esp; }
   void      setSP(uint32_t value)  { _registers.__esp = value; }
   uint32_t  getIP() const          { return _registers.__eip; }
   void      setIP(uint32_t value)  { _registers.__eip = value; }
   uint32_t  getEBP() const         { return _registers.__ebp; }
   void      setEBP(uint32_t value) { _registers.__ebp = value; }
   uint32_t  getEBX() const         { return _registers.__ebx; }
public:
   bool        validFloatRegister(int) const { return false; }
   double      getFloatRegister(int num) const;
   void        setFloatRegister(int num, double value);
   bool        validVectorRegister(int) const { return false; }
   v128        getVectorRegister(int num) const;
   void        setVectorRegister(int num, v128 value);
   const char *getRegisterName(int num);
   void        jumpto();
-  static int  lastDwarfRegNum() { return 16; }
+  static int  lastDwarfRegNum() { return _LIBUNWIND_HIGHEST_DWARF_REGISTER; }
 
   uint64_t  getSP() const          { return _registers.__rsp; }
   void      setSP(uint64_t value)  { _registers.__rsp = value; }
   uint64_t  getIP() const          { return _registers.__rip; }
   void      setIP(uint64_t value)  { _registers.__rip = value; }
   uint64_t  getRBP() const         { return _registers.__rbp; }
   void      setRBP(uint64_t value) { _registers.__rbp = value; }
   uint64_t  getRBX() const         { return _registers.__rbx; }
public:
   bool        validFloatRegister(int num) const;
   double      getFloatRegister(int num) const;
   void        setFloatRegister(int num, double value);
   bool        validVectorRegister(int num) const;
   v128        getVectorRegister(int num) const;
   void        setVectorRegister(int num, v128 value);
   const char *getRegisterName(int num);
   void        jumpto();
-  static int  lastDwarfRegNum() { return 112; }
+  static int  lastDwarfRegNum() { return _LIBUNWIND_HIGHEST_DWARF_REGISTER; }
 
   uint64_t  getSP() const         { return _registers.__r1; }
   void      setSP(uint32_t value) { _registers.__r1 = value; }
   uint64_t  getIP() const         { return _registers.__srr0; }
   void      setIP(uint32_t value) { _registers.__srr0 = value; }
 
 private:
   struct ppc_thread_state_t {
public:
   bool        validFloatRegister(int num) const;
   double      getFloatRegister(int num) const;
   void        setFloatRegister(int num, double value);
   bool        validVectorRegister(int num) const;
   v128        getVectorRegister(int num) const;
   void        setVectorRegister(int num, v128 value);
   const char *getRegisterName(int num);
   void        jumpto();
-  static int  lastDwarfRegNum() { return 95; }
+  static int  lastDwarfRegNum() { return _LIBUNWIND_HIGHEST_DWARF_REGISTER; }
 
   uint64_t  getSP() const         { return _registers.__sp; }
   void      setSP(uint64_t value) { _registers.__sp = value; }
   uint64_t  getIP() const         { return _registers.__pc; }
   void      setIP(uint64_t value) { _registers.__pc = value; }
   uint64_t  getFP() const         { return _registers.__fp; }
   void      setFP(uint64_t value) { _registers.__fp = value; }
 
public:
   bool        validFloatRegister(int num) const;
   double      getFloatRegister(int num) const;
   void        setFloatRegister(int num, double value);
   bool        validVectorRegister(int num) const;
   v128        getVectorRegister(int num) const;
   void        setVectorRegister(int num, v128 value);
   const char *getRegisterName(int num);
   void        jumpto();
-  static int  lastDwarfRegNum() { return 31; }
+  static int  lastDwarfRegNum() { return _LIBUNWIND_HIGHEST_DWARF_REGISTER; }
 
   uint64_t  getSP() const         { return _registers.__r[1]; }
   void      setSP(uint32_t value) { _registers.__r[1] = value; }
   uint64_t  getIP() const         { return _registers.__r[9]; }
   void      setIP(uint32_t value) { _registers.__r[9] = value; }
 
 private:
   struct or1k_thread_state_t {