regs.h (HARD_REGNO_CALL_PART_CLOBBERED): New macro.

        * regs.h (HARD_REGNO_CALL_PART_CLOBBERED):  New macro.
        * local-alloc.c (find_free_reg): Use it.
        * global.c (find_reg): Likewise.
        * tm.texi: Document HARD_REGNO_CALL_PART_CLOBBERED.

From-SVN: r22688

gcc/ChangeLog

@@ -24,6 +24,11 @@ Wed Sep 30 18:29:26 1998  Jeffrey A Law  (law@cygnus.com)
 
 Wed Sep 30 18:19:27 1998  Michael Hayes  <m.hayes@elec.canterbury.ac.nz>
 
+	* regs.h (HARD_REGNO_CALL_PART_CLOBBERED):  New macro.
+	* local-alloc.c (find_free_reg): Use it.
+	* global.c (find_reg): Likewise.
+	* tm.texi: Document HARD_REGNO_CALL_PART_CLOBBERED.
+
 	* regs.h (HARD_REGNO_CALLER_SAVE_MODE): New macro.
 	* caller-save.c (init_caller_save): Use it.
 	* tm.texi: Document HARD_REGNO_CALLER_SAVE_MODE.

gcc/global.c

@@ -976,7 +976,10 @@ find_reg (allocno, losers, alt_regs_p, accept_call_clobbered, retrying)
 	  int regno = i;
 #endif
 	  if (! TEST_HARD_REG_BIT (used, regno)
-	      && HARD_REGNO_MODE_OK (regno, mode))
+	      && HARD_REGNO_MODE_OK (regno, mode)
+	      && (allocno_calls_crossed[allocno] == 0
+		  || accept_call_clobbered
+		  || ! HARD_REGNO_CALL_PART_CLOBBERED (regno, mode)))
 	    {
 	      register int j;
 	      register int lim = regno + HARD_REGNO_NREGS (regno, mode);

gcc/local-alloc.c

@@ -2043,7 +2043,10 @@ find_free_reg (class, mode, qty, accept_call_clobbered, just_try_suggested,
       int regno = i;
 #endif
       if (! TEST_HARD_REG_BIT (first_used, regno)
-	  && HARD_REGNO_MODE_OK (regno, mode))
+	  && HARD_REGNO_MODE_OK (regno, mode)
+	  && (qty_n_calls_crossed[qty] == 0
+	      || accept_call_clobbered
+	      || ! HARD_REGNO_CALL_PART_CLOBBERED (regno, mode)))
 	{
 	  register int j;
 	  register int size1 = HARD_REGNO_NREGS (regno, mode);

gcc/regs.h

@@ -217,6 +217,12 @@ extern int caller_save_needed;
   choose_hard_reg_mode (REGNO, NREGS)
 #endif
 
+/* Registers that get partially clobbered by a call in a given mode. 
+   These must not be call used registers.  */
+#ifndef HARD_REGNO_CALL_PART_CLOBBERED
+#define HARD_REGNO_CALL_PART_CLOBBERED(REGNO, MODE) 0
+#endif
+
 /* Allocated in local_alloc.  */
 
 /* A list of SCRATCH rtl allocated by local-alloc.  */

gcc/tm.texi

@@ -1333,6 +1333,17 @@ If a register has 0 in @code{CALL_USED_REGISTERS}, the compiler
 automatically saves it on function entry and restores it on function
 exit, if the register is used within the function.
 
+@findex HARD_REGNO_CALL_PART_CLOBBERED
+@item HARD_REGNO_CALL_PART_CLOBBERED (@var{regno}, @var{mode})
+@cindex call-used register
+@cindex call-clobbered register
+@cindex call-saved register
+A C expression that is non-zero if it is not permissible to store a
+value of mode @var{mode} in hard register number @var{regno} across a
+call without some part of it being clobbered.  For most machines this
+macro need not be defined.  It is only required for machines that do not
+preserve the entire contents of a register across a call.
+
 @findex CONDITIONAL_REGISTER_USAGE
 @findex fixed_regs
 @findex call_used_regs