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, 17 insertions, 21 deletions

diff --git a/gcc/reload.c b/gcc/reload.c
index 2116332..e0793cf 100644
--- a/gcc/reload.c
+++ b/gcc/reload.c
@@ -1071,8 +1071,7 @@ push_reload (rtx in, rtx out, rtx *inloc, rtx *outloc,
 		      && paradoxical_subreg_p (inmode, inner_mode)
 		      && LOAD_EXTEND_OP (inner_mode) != UNKNOWN)
 		  || (WORD_REGISTER_OPERATIONS
-		      && (GET_MODE_PRECISION (inmode)
-			  < GET_MODE_PRECISION (GET_MODE (SUBREG_REG (in))))
+		      && partial_subreg_p (inmode, GET_MODE (SUBREG_REG (in)))
 		      && ((GET_MODE_SIZE (inmode) - 1) / UNITS_PER_WORD ==
 			  ((GET_MODE_SIZE (GET_MODE (SUBREG_REG (in))) - 1)
 			   / UNITS_PER_WORD)))))
@@ -1171,8 +1170,7 @@ push_reload (rtx in, rtx out, rtx *inloc, rtx *outloc,
 	       || MEM_P (SUBREG_REG (out)))
 	      && (paradoxical_subreg_p (outmode, GET_MODE (SUBREG_REG (out)))
 		  || (WORD_REGISTER_OPERATIONS
-		      && (GET_MODE_PRECISION (outmode)
-			  < GET_MODE_PRECISION (GET_MODE (SUBREG_REG (out))))
+		      && partial_subreg_p (outmode, GET_MODE (SUBREG_REG (out)))
 		      && ((GET_MODE_SIZE (outmode) - 1) / UNITS_PER_WORD ==
 			  ((GET_MODE_SIZE (GET_MODE (SUBREG_REG (out))) - 1)
 			   / UNITS_PER_WORD)))))
@@ -1417,10 +1415,10 @@ push_reload (rtx in, rtx out, rtx *inloc, rtx *outloc,
       /* The modes can be different.  If they are, we want to reload in
 	 the larger mode, so that the value is valid for both modes.  */
       if (inmode != VOIDmode
-	  && GET_MODE_SIZE (inmode) > GET_MODE_SIZE (rld[i].inmode))
+	  && partial_subreg_p (rld[i].inmode, inmode))
 	rld[i].inmode = inmode;
       if (outmode != VOIDmode
-	  && GET_MODE_SIZE (outmode) > GET_MODE_SIZE (rld[i].outmode))
+	  && partial_subreg_p (rld[i].outmode, outmode))
 	rld[i].outmode = outmode;
       if (in != 0)
 	{
@@ -1462,26 +1460,25 @@ push_reload (rtx in, rtx out, rtx *inloc, rtx *outloc,
 	     overwrite the operands only when the new mode is larger.
 	     See also PR33613.  */
 	  if (!rld[i].in
-	      || GET_MODE_SIZE (GET_MODE (in))
-	           > GET_MODE_SIZE (GET_MODE (rld[i].in)))
+	      || partial_subreg_p (GET_MODE (rld[i].in), GET_MODE (in)))
 	    rld[i].in = in;
 	  if (!rld[i].in_reg
 	      || (in_reg
-		  && GET_MODE_SIZE (GET_MODE (in_reg))
-	             > GET_MODE_SIZE (GET_MODE (rld[i].in_reg))))
+		  && partial_subreg_p (GET_MODE (rld[i].in_reg),
+				       GET_MODE (in_reg))))
 	    rld[i].in_reg = in_reg;
 	}
       if (out != 0)
 	{
 	  if (!rld[i].out
 	      || (out
-		  && GET_MODE_SIZE (GET_MODE (out))
-	             > GET_MODE_SIZE (GET_MODE (rld[i].out))))
+		  && partial_subreg_p (GET_MODE (rld[i].out),
+				       GET_MODE (out))))
 	    rld[i].out = out;
 	  if (outloc
 	      && (!rld[i].out_reg
-		  || GET_MODE_SIZE (GET_MODE (*outloc))
-		     > GET_MODE_SIZE (GET_MODE (rld[i].out_reg))))
+		  || partial_subreg_p (GET_MODE (rld[i].out_reg),
+				       GET_MODE (*outloc))))
 	    rld[i].out_reg = *outloc;
 	}
       if (reg_class_subset_p (rclass, rld[i].rclass))
@@ -1587,7 +1584,7 @@ push_reload (rtx in, rtx out, rtx *inloc, rtx *outloc,
       int regno;
       machine_mode rel_mode = inmode;
 
-      if (out && GET_MODE_SIZE (outmode) > GET_MODE_SIZE (inmode))
+      if (out && partial_subreg_p (rel_mode, outmode))
 	rel_mode = outmode;
 
       for (note = REG_NOTES (this_insn); note; note = XEXP (note, 1))
@@ -4554,11 +4551,10 @@ find_reloads (rtx_insn *insn, int replace, int ind_levels, int live_known,
   /* Compute reload_mode and reload_nregs.  */
   for (i = 0; i < n_reloads; i++)
     {
-      rld[i].mode
-	= (rld[i].inmode == VOIDmode
-	   || (GET_MODE_SIZE (rld[i].outmode)
-	       > GET_MODE_SIZE (rld[i].inmode)))
-	  ? rld[i].outmode : rld[i].inmode;
+      rld[i].mode = rld[i].inmode;
+      if (rld[i].mode == VOIDmode
+	  || partial_subreg_p (rld[i].mode, rld[i].outmode))
+	rld[i].mode = rld[i].outmode;
 
       rld[i].nregs = ira_reg_class_max_nregs [rld[i].rclass][rld[i].mode];
     }
@@ -6162,7 +6158,7 @@ find_reloads_subreg_address (rtx x, int opnum, enum reload_type type,
     return NULL;
 
   if (WORD_REGISTER_OPERATIONS
-      && GET_MODE_SIZE (outer_mode) < GET_MODE_SIZE (inner_mode)
+      && partial_subreg_p (outer_mode, inner_mode)
       && ((GET_MODE_SIZE (outer_mode) - 1) / UNITS_PER_WORD
           == (GET_MODE_SIZE (inner_mode) - 1) / UNITS_PER_WORD))
     return NULL;