This file contains the relevant part of config/sparc/sparc.h from the
GNU C source code which describes how each register is used.

#define REGISTER_NAMES \
{"%g0", "%g1", "%g2", "%g3", "%g4", "%g5", "%g6", "%g7",		\
 "%o0", "%o1", "%o2", "%o3", "%o4", "%o5", "%sp", "%o7",		\
 "%l0", "%l1", "%l2", "%l3", "%l4", "%l5", "%l6", "%l7",		\
 "%i0", "%i1", "%i2", "%i3", "%i4", "%i5", "%fp", "%i7",		\
 "%f0", "%f1", "%f2", "%f3", "%f4", "%f5", "%f6", "%f7",		\
 "%f8", "%f9", "%f10", "%f11", "%f12", "%f13", "%f14", "%f15",		\
 "%f16", "%f17", "%f18", "%f19", "%f20", "%f21", "%f22", "%f23",	\
 "%f24", "%f25", "%f26", "%f27", "%f28", "%f29", "%f30", "%f31"}

/* 1 for registers that have pervasive standard uses
   and are not available for the register allocator.

   On non-v9 systems:
   g1 is free to use as temporary.
   g2-g4 are reserved for applications.  Gcc normally uses them as
   temporaries, but this can be disabled via the -mno-app-regs option.
   g5 through g7 are reserved for the operating system.

   On v9 systems:
   g1,g5 are free to use as temporaries, and are free to use between calls
   if the call is to an external function via the PLT.
   g4 is free to use as a temporary in the non-embedded case.
   g4 is reserved in the embedded case.
   g2-g3 are reserved for applications.  Gcc normally uses them as
   temporaries, but this can be disabled via the -mno-app-regs option.
   g6-g7 are reserved for the operating system (or application in
   embedded case).
   ??? Register 1 is used as a temporary by the 64 bit sethi pattern, so must
   currently be a fixed register until this pattern is rewritten.
   Register 1 is also used when restoring call-preserved registers in large
   stack frames.

   Registers fixed in arch32 and not arch64 (or vice-versa) are marked in
   CONDITIONAL_REGISTER_USAGE in order to properly handle -ffixed-.
*/

#define FIXED_REGISTERS  \
 {1, 0, 0, 0, 0, 0, 1, 1,	\
  0, 0, 0, 0, 0, 0, 1, 0,	\
  0, 0, 0, 0, 0, 0, 0, 0,	\
  0, 0, 0, 0, 0, 0, 1, 1,	\
				\
  0, 0, 0, 0, 0, 0, 0, 0,	\
  0, 0, 0, 0, 0, 0, 0, 0,	\
  0, 0, 0, 0, 0, 0, 0, 0,	\
  0, 0, 0, 0, 0, 0, 0, 0,	\
				\
  0, 0, 0, 0, 0, 0, 0, 0,	\
  0, 0, 0, 0, 0, 0, 0, 0,	\
  0, 0, 0, 0, 0, 0, 0, 0,	\
  0, 0, 0, 0, 0, 0, 0, 0,	\
				\
  0, 0, 0, 0, 0}

/* 1 for registers not available across function calls.
   These must include the FIXED_REGISTERS and also any
   registers that can be used without being saved.
   The latter must include the registers where values are returned
   and the register where structure-value addresses are passed.
   Aside from that, you can include as many other registers as you like.  */

#define CALL_USED_REGISTERS  \
 {1, 1, 1, 1, 1, 1, 1, 1,	\
  1, 1, 1, 1, 1, 1, 1, 1,	\
  0, 0, 0, 0, 0, 0, 0, 0,	\
  0, 0, 0, 0, 0, 0, 1, 1,	\
				\
  1, 1, 1, 1, 1, 1, 1, 1,	\
  1, 1, 1, 1, 1, 1, 1, 1,	\
  1, 1, 1, 1, 1, 1, 1, 1,	\
  1, 1, 1, 1, 1, 1, 1, 1,	\
				\
  1, 1, 1, 1, 1, 1, 1, 1,	\
  1, 1, 1, 1, 1, 1, 1, 1,	\
  1, 1, 1, 1, 1, 1, 1, 1,	\
  1, 1, 1, 1, 1, 1, 1, 1,	\
				\
  1, 1, 1, 1, 1}

/* If !TARGET_FPU, then make the fp registers and fp cc regs fixed so that
   they won't be allocated.  */

#define CONDITIONAL_REGISTER_USAGE				\
do								\
  {								\
    if (TARGET_ARCH32)						\
      {								\
	fixed_regs[5] = 1;					\
      }								\
    else							\
      {								\
	fixed_regs[1] = 1;					\
      }								\
    if (! TARGET_V9)						\
      {								\
	int regno;						\
	for (regno = SPARC_FIRST_V9_FP_REG;			\
	     regno <= SPARC_LAST_V9_FP_REG;			\
	     regno++)						\
	  fixed_regs[regno] = 1;				\
	/* %fcc0 is used by v8 and v9.  */			\
	for (regno = SPARC_FIRST_V9_FCC_REG + 1;		\
	     regno <= SPARC_LAST_V9_FCC_REG;			\
	     regno++)						\
	  fixed_regs[regno] = 1;				\
      }								\
    if (! TARGET_FPU)						\
      {								\
	int regno;						\
	for (regno = 32; regno < SPARC_LAST_V9_FCC_REG; regno++) \
	  fixed_regs[regno] = 1;				\
      }								\
    /* Don't unfix g2-g4 if they were fixed with -ffixed-.  */	\
    fixed_regs[2] |= ! TARGET_APP_REGS;				\
    fixed_regs[3] |= ! TARGET_APP_REGS;				\
    fixed_regs[4] |= ! TARGET_APP_REGS || TARGET_CM_EMBMEDANY;	\
    if (TARGET_FLAT)						\
      {								\
	/* Let the compiler believe the frame pointer is still	\
	   %fp, but output it as %i7.  */			\
	fixed_regs[31] = 1;					\
	reg_names[FRAME_POINTER_REGNUM] = "%i7";		\
	/* ??? This is a hack to disable leaf functions.  */	\
	global_regs[7] = 1;					\
      }								\
    if (profile_block_flag)					\
      {								\
	/* %g1 and %g2 must be fixed, because BLOCK_PROFILER	\
	    uses them.  */					\
	fixed_regs[1] = 1;					\
	fixed_regs[2] = 1;					\
      }								\
    if (flag_pic != 0)						\
      {								\
        fixed_regs[23] = 1;					\
        call_used_regs[23] = 1;					\
      }								\
  }								\
while (0)