try multi-reg dest in default_zero_call_used_regs

When the mode of regno_reg_rtx is not hard_regno_mode_ok for the
target, try grouping the register with subsequent ones.  This enables
s16 to s31 and their hidden pairs to be zeroed with the default logic
on some arm variants.


for  gcc/ChangeLog

	* targhooks.cc (default_zero_call_used_regs): Attempt to group
	regs that the target refuses to use in their natural modes.
	(zcur_select_mode_rtx): New.
	* regs.h (struct target_regs): Add x_hard_regno_max_nregs.
	(hard_regno_max_nregs): Define.
	* reginfo.cc (init_reg_modes_target): Set hard_regno_max_nregs.

1 files changed, 5 insertions, 0 deletions

diff --git a/gcc/regs.h b/gcc/regs.h
index 74f1f63..f72b06f 100644
--- a/gcc/regs.h
+++ b/gcc/regs.h
@@ -202,6 +202,9 @@ struct target_regs {
      registers that a given machine mode occupies.  */
   unsigned char x_hard_regno_nregs[FIRST_PSEUDO_REGISTER][MAX_MACHINE_MODE];
 
+  /* The max value found in x_hard_regno_nregs.  */
+  unsigned char x_hard_regno_max_nregs;
+
   /* For each hard register, the widest mode object that it can contain.
      This will be a MODE_INT mode if the register can hold integers.  Otherwise
      it will be a MODE_FLOAT or a MODE_CC mode, whichever is valid for the
@@ -235,6 +238,8 @@ extern struct target_regs *this_target_regs;
 #else
 #define this_target_regs (&default_target_regs)
 #endif
+#define hard_regno_max_nregs \
+  (this_target_regs->x_hard_regno_max_nregs)
 #define reg_raw_mode \
   (this_target_regs->x_reg_raw_mode)
 #define have_regs_of_mode \