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Prevent invalid register mode changes in combine

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This patch stops combine from changing the mode of an existing register
in-place if doing so would change the size of the underlying register
allocation size, as given by REGMODE_NATURAL_SIZE.  Without this,
many tests fail in adjust_reg_mode after SVE is added.  One example
is gcc.c-torture/compile/20090401-1.c.

2017-10-13  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* combine.c (can_change_dest_mode): Reject changes in
	REGMODE_NATURAL_SIZE.

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

From-SVN: r253717
This commit is contained in:
Richard Sandiford 2017-10-13 09:58:23 +00:00 committed by Richard Sandiford
parent 250a60f387
commit 8649149a3c
2 changed files with 13 additions and 0 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2017-10-13 Richard Sandiford <richard.sandiford@linaro.org>
Alan Hayward <alan.hayward@arm.com>
David Sherwood <david.sherwood@arm.com>
* combine.c (can_change_dest_mode): Reject changes in
REGMODE_NATURAL_SIZE.
2017-10-13 Richard Sandiford <richard.sandiford@linaro.org>
Alan Hayward <alan.hayward@arm.com>
David Sherwood <david.sherwood@arm.com>

6
gcc/combine.c
View File

@ -2475,6 +2475,12 @@ can_change_dest_mode (rtx x, int added_sets, machine_mode mode)
if (!REG_P (x))
return false;
/* Don't change between modes with different underlying register sizes,
since this could lead to invalid subregs. */
if (REGMODE_NATURAL_SIZE (mode)
!= REGMODE_NATURAL_SIZE (GET_MODE (x)))
return false;
regno = REGNO (x);
/* Allow hard registers if the new mode is legal, and occupies no more
registers than the old mode. */