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Add narrower_subreg_mode helper function 

This patch adds a narrowing equivalent of wider_subreg_mode.  At present
there is only one user.

2017-11-01  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* rtl.h (narrower_subreg_mode): New function.
	* ira-color.c (update_costs_from_allocno): Use it.

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

From-SVN: r254304
This commit is contained in:
Richard Sandiford 2017-11-01 12:52:50 +00:00 committed by Richard Sandiford
parent 4b926feae1
commit b3ad445f85
3 changed files with 25 additions and 9 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2017-11-01 Richard Sandiford <richard.sandiford@linaro.org>
Alan Hayward <alan.hayward@arm.com>
David Sherwood <david.sherwood@arm.com>
* rtl.h (narrower_subreg_mode): New function.
* ira-color.c (update_costs_from_allocno): Use it.
2017-11-01 Richard Sandiford <richard.sandiford@linaro.org>
Alan Hayward <alan.hayward@arm.com>
David Sherwood <david.sherwood@arm.com>

17
gcc/ira-color.c
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@ -1367,15 +1367,14 @@ update_costs_from_allocno (ira_allocno_t allocno, int hard_regno,
|| ALLOCNO_ASSIGNED_P (another_allocno))
continue;
if (GET_MODE_SIZE (ALLOCNO_MODE (cp->second)) < GET_MODE_SIZE (mode))
/* If we have different modes use the smallest one. It is
a sub-register move. It is hard to predict what LRA
will reload (the pseudo or its sub-register) but LRA
will try to minimize the data movement. Also for some
register classes bigger modes might be invalid,
e.g. DImode for AREG on x86. For such cases the
register move cost will be maximal. */
mode = ALLOCNO_MODE (cp->second);
/* If we have different modes use the smallest one. It is
a sub-register move. It is hard to predict what LRA
will reload (the pseudo or its sub-register) but LRA
will try to minimize the data movement. Also for some
register classes bigger modes might be invalid,
e.g. DImode for AREG on x86. For such cases the
register move cost will be maximal. */
mode = narrower_subreg_mode (mode, ALLOCNO_MODE (cp->second));
cost = (cp->second == allocno
? ira_register_move_cost[mode][rclass][aclass]

10
gcc/rtl.h
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@ -2954,6 +2954,16 @@ subreg_lowpart_offset (machine_mode outermode, machine_mode innermode)
GET_MODE_SIZE (innermode));
}
/* Given that a subreg has outer mode OUTERMODE and inner mode INNERMODE,
return the smaller of the two modes if they are different sizes,
otherwise return the outer mode. */
inline machine_mode
narrower_subreg_mode (machine_mode outermode, machine_mode innermode)
{
return paradoxical_subreg_p (outermode, innermode) ? innermode : outermode;
}
/* Given that a subreg has outer mode OUTERMODE and inner mode INNERMODE,
return the mode that is big enough to hold both the outer and inner
values. Prefer the outer mode in the event of a tie. */