Add a partial_subreg_p predicate

This patch adds a partial_subreg_p predicate to go alongside
paradoxical_subreg_p.

Like the paradoxical_subreg_p patch, this one replaces some tests that
were based on GET_MODE_SIZE rather than GET_MODE_PRECISION.  In each
case the change should be a no-op or an improvement.

The regcprop.c patch prevents some replacements of the 82-bit RFmode
with the 80-bit XFmode on ia64.  I don't understand the target details
here particularly well, but from the way the modes are described in
ia64-modes.def, it isn't valid to assume that an XFmode can carry an
RFmode payload.  A comparison of the testsuite assembly output for one
target per CPU showed no other differences.

Some of the places changed here are tracking the widest access mode
found for a register.  The series tries to standardise on:

  if (partial_subreg_p (widest_seen, new_mode))
    widest_seen = new_mode;

rather than:

  if (paradoxical_subreg_p (new_mode, widest_seen))
    widest_seen = new_mode;

Either would have been OK.

2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* rtl.h (partial_subreg_p): New function.
	* caller-save.c (save_call_clobbered_regs): Use it.
	* calls.c (expand_call): Likewise.
	* combine.c (combinable_i3pat): Likewise.
	(simplify_set): Likewise.
	(make_extraction): Likewise.
	(make_compound_operation_int): Likewise.
	(gen_lowpart_or_truncate): Likewise.
	(force_to_mode): Likewise.
	(make_field_assignment): Likewise.
	(reg_truncated_to_mode): Likewise.
	(record_truncated_value): Likewise.
	(move_deaths): Likewise.
	* cse.c (record_jump_cond): Likewise.
	(cse_insn): Likewise.
	* cselib.c (cselib_lookup_1): Likewise.
	* expmed.c (extract_bit_field_using_extv): Likewise.
	* function.c (assign_parm_setup_reg): Likewise.
	* ifcvt.c (noce_convert_multiple_sets): Likewise.
	* ira-build.c (create_insn_allocnos): Likewise.
	* lra-coalesce.c (merge_pseudos): Likewise.
	* lra-constraints.c (match_reload): Likewise.
	(simplify_operand_subreg): Likewise.
	(curr_insn_transform): Likewise.
	* lra-lives.c (process_bb_lives): Likewise.
	* lra.c (new_insn_reg): Likewise.
	(lra_substitute_pseudo): Likewise.
	* regcprop.c (mode_change_ok): Likewise.
	(maybe_mode_change): Likewise.
	(copyprop_hardreg_forward_1): Likewise.
	* reload.c (push_reload): Likewise.
	(find_reloads): Likewise.
	(find_reloads_subreg_address): Likewise.
	* reload1.c (alter_reg): Likewise.
	(eliminate_regs_1): Likewise.
	* simplify-rtx.c (simplify_unary_operation_1): Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r251536

1 files changed, 4 insertions, 6 deletions

diff --git a/gcc/lra-constraints.c b/gcc/lra-constraints.c
index 3ebc803..6da910e 100644
--- a/gcc/lra-constraints.c
+++ b/gcc/lra-constraints.c
@@ -928,7 +928,7 @@ match_reload (signed char out, signed char *ins, signed char *outs,
   push_to_sequence (*before);
   if (inmode != outmode)
     {
-      if (GET_MODE_SIZE (inmode) > GET_MODE_SIZE (outmode))
+      if (partial_subreg_p (outmode, inmode))
 	{
 	  reg = new_in_reg
 	    = lra_create_new_reg_with_unique_value (inmode, in_rtx,
@@ -1579,8 +1579,7 @@ simplify_operand_subreg (int nop, machine_mode reg_mode)
 	      bitmap_set_bit (&lra_subreg_reload_pseudos, REGNO (new_reg));
 
 	      insert_before = (type != OP_OUT
-			       || GET_MODE_SIZE (innermode)
-				    > GET_MODE_SIZE (mode));
+			       || partial_subreg_p (mode, innermode));
 	      insert_after = type != OP_IN;
 	      insert_move_for_subreg (insert_before ? &before : NULL,
 				      insert_after ? &after : NULL,
@@ -3939,8 +3938,7 @@ curr_insn_transform (bool check_only_p)
       lra_assert (out >= 0 && in >= 0
 		  && curr_static_id->operand[out].type == OP_OUT
 		  && curr_static_id->operand[in].type == OP_IN);
-      rld = (GET_MODE_SIZE (GET_MODE (dest)) <= GET_MODE_SIZE (GET_MODE (src))
-	     ? dest : src);
+      rld = partial_subreg_p (GET_MODE (src), GET_MODE (dest)) ? src : dest;
       rld_mode = GET_MODE (rld);
 #ifdef SECONDARY_MEMORY_NEEDED_MODE
       sec_mode = SECONDARY_MEMORY_NEEDED_MODE (rld_mode);
@@ -3950,7 +3948,7 @@ curr_insn_transform (bool check_only_p)
       new_reg = lra_create_new_reg (sec_mode, NULL_RTX,
 				    NO_REGS, "secondary");
       /* If the mode is changed, it should be wider.  */
-      lra_assert (GET_MODE_SIZE (sec_mode) >= GET_MODE_SIZE (rld_mode));
+      lra_assert (!partial_subreg_p (sec_mode, rld_mode));
       if (sec_mode != rld_mode)
         {
 	  /* If the target says specifically to use another mode for