Add wider_subreg_mode helper functions

This patch adds helper functions that say which of the two modes
involved in a subreg is the larger, preferring the outer mode in
the event of a tie.  It also converts IRA and reload to track modes
instead of byte sizes, since this is slightly more convenient when
variable-sized modes are added later.

2017-10-26  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* rtl.h (wider_subreg_mode): New function.
	* ira.h (ira_sort_regnos_for_alter_reg): Take a machine_mode *
	rather than an unsigned int *.
	* ira-color.c (regno_max_ref_width): Replace with...
	(regno_max_ref_mode): ...this new variable.
	(coalesced_pseudo_reg_slot_compare): Update accordingly.
	Use wider_subreg_mode.
	(ira_sort_regnos_for_alter_reg): Likewise.  Take a machine_mode *
	rather than an unsigned int *.
	* lra-constraints.c (uses_hard_regs_p): Use wider_subreg_mode.
	(process_alt_operands): Likewise.
	(invariant_p): Likewise.
	* lra-spills.c (assign_mem_slot): Likewise.
	(add_pseudo_to_slot): Likewise.
	* lra.c (collect_non_operand_hard_regs): Likewise.
	(add_regs_to_insn_regno_info): Likewise.
	* reload1.c (regno_max_ref_width): Replace with...
	(regno_max_ref_mode): ...this new variable.
	(reload): Update accordingly.  Update call to
	ira_sort_regnos_for_alter_reg.
	(alter_reg): Update to use regno_max_ref_mode.  Call wider_subreg_mode.
	(init_eliminable_invariants): Update to use regno_max_ref_mode.
	(scan_paradoxical_subregs): Likewise.

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

From-SVN: r254115

1 files changed, 17 insertions, 15 deletions

diff --git a/gcc/reload1.c b/gcc/reload1.c
index e2ee2feda93..e15bd8a2c1a 100644
--- a/gcc/reload1.c
+++ b/gcc/reload1.c
@@ -97,8 +97,8 @@ static regset_head reg_has_output_reload;
    in the current insn.  */
 static HARD_REG_SET reg_is_output_reload;
 
-/* Widest width in which each pseudo reg is referred to (via subreg).  */
-static unsigned int *reg_max_ref_width;
+/* Widest mode in which each pseudo reg is referred to (via subreg).  */
+static machine_mode *reg_max_ref_mode;
 
 /* Vector to remember old contents of reg_renumber before spilling.  */
 static short *reg_old_renumber;
@@ -830,7 +830,7 @@ reload (rtx_insn *first, int global)
   if (ira_conflicts_p)
     /* Ask IRA to order pseudo-registers for better stack slot
        sharing.  */
-    ira_sort_regnos_for_alter_reg (temp_pseudo_reg_arr, n, reg_max_ref_width);
+    ira_sort_regnos_for_alter_reg (temp_pseudo_reg_arr, n, reg_max_ref_mode);
 
   for (i = 0; i < n; i++)
     alter_reg (temp_pseudo_reg_arr[i], -1, false);
@@ -1252,7 +1252,7 @@ reload (rtx_insn *first, int global)
   /* Indicate that we no longer have known memory locations or constants.  */
   free_reg_equiv ();
 
-  free (reg_max_ref_width);
+  free (reg_max_ref_mode);
   free (reg_old_renumber);
   free (pseudo_previous_regs);
   free (pseudo_forbidden_regs);
@@ -2142,8 +2142,9 @@ alter_reg (int i, int from_reg, bool dont_share_p)
       machine_mode mode = GET_MODE (regno_reg_rtx[i]);
       unsigned int inherent_size = PSEUDO_REGNO_BYTES (i);
       unsigned int inherent_align = GET_MODE_ALIGNMENT (mode);
-      unsigned int total_size = MAX (inherent_size, reg_max_ref_width[i]);
-      unsigned int min_align = reg_max_ref_width[i] * BITS_PER_UNIT;
+      machine_mode wider_mode = wider_subreg_mode (mode, reg_max_ref_mode[i]);
+      unsigned int total_size = GET_MODE_SIZE (wider_mode);
+      unsigned int min_align = GET_MODE_BITSIZE (reg_max_ref_mode[i]);
       int adjust = 0;
 
       something_was_spilled = true;
@@ -4083,9 +4084,9 @@ init_eliminable_invariants (rtx_insn *first, bool do_subregs)
 
   grow_reg_equivs ();
   if (do_subregs)
-    reg_max_ref_width = XCNEWVEC (unsigned int, max_regno);
+    reg_max_ref_mode = XCNEWVEC (machine_mode, max_regno);
   else
-    reg_max_ref_width = NULL;
+    reg_max_ref_mode = NULL;
 
   num_eliminable_invariants = 0;
 
@@ -4404,7 +4405,7 @@ finish_spills (int global)
   return something_changed;
 }
 
-/* Find all paradoxical subregs within X and update reg_max_ref_width.  */
+/* Find all paradoxical subregs within X and update reg_max_ref_mode.  */
 
 static void
 scan_paradoxical_subregs (rtx x)
@@ -4427,13 +4428,14 @@ scan_paradoxical_subregs (rtx x)
       return;
 
     case SUBREG:
-      if (REG_P (SUBREG_REG (x))
-	  && (GET_MODE_SIZE (GET_MODE (x))
-	      > reg_max_ref_width[REGNO (SUBREG_REG (x))]))
+      if (REG_P (SUBREG_REG (x)))
 	{
-	  reg_max_ref_width[REGNO (SUBREG_REG (x))]
-	    = GET_MODE_SIZE (GET_MODE (x));
-	  mark_home_live_1 (REGNO (SUBREG_REG (x)), GET_MODE (x));
+	  unsigned int regno = REGNO (SUBREG_REG (x));
+	  if (partial_subreg_p (reg_max_ref_mode[regno], GET_MODE (x)))
+	    {
+	      reg_max_ref_mode[regno] = GET_MODE (x);
+	      mark_home_live_1 (regno, GET_MODE (x));
+	    }
 	}
       return;