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, 3 insertions, 3 deletions

diff --git a/gcc/lra.c b/gcc/lra.c
index affec0c5948..61e40eebe3f 100644
--- a/gcc/lra.c
+++ b/gcc/lra.c
@@ -546,8 +546,8 @@ new_insn_reg (rtx_insn *insn, int regno, enum op_type type,
   lra_insn_reg *ir = lra_insn_reg_pool.allocate ();
   ir->type = type;
   ir->biggest_mode = mode;
-  if (GET_MODE_SIZE (mode) > GET_MODE_SIZE (lra_reg_info[regno].biggest_mode)
-      && NONDEBUG_INSN_P (insn))
+  if (NONDEBUG_INSN_P (insn)
+      && partial_subreg_p (lra_reg_info[regno].biggest_mode, mode))
     lra_reg_info[regno].biggest_mode = mode;
   ir->subreg_p = subreg_p;
   ir->early_clobber = early_clobber;
@@ -1913,7 +1913,7 @@ lra_substitute_pseudo (rtx *loc, int old_regno, rtx new_reg, bool subreg_p)
       if (mode != inner_mode
 	  && ! (CONST_INT_P (new_reg) && SCALAR_INT_MODE_P (mode)))
 	{
-	  if (GET_MODE_SIZE (mode) >= GET_MODE_SIZE (inner_mode)
+	  if (!partial_subreg_p (mode, inner_mode)
 	      || ! SCALAR_INT_MODE_P (inner_mode))
 	    new_reg = gen_rtx_SUBREG (mode, new_reg, 0);
 	  else