r273572 - in /trunk/gcc: ChangeLog config/arm/a...

[rearnsha@gcc.gnu.org]

Author: rearnsha
Date: Thu Jul 18 13:56:52 2019
New Revision: 273572

URL: https://gcc.gnu.org/viewcvs?rev=273572&root=gcc&view=rev
Log:
[arm] Fix incorrect modes with 'borrow' operations

Looking through the arm backend I noticed that the modes used to pass
comparison types into subtract-with-carry operations were being
incorrectly set.  The result is that the compiler is not truly
self-consistent.  To clean this up I've introduced a new predicate,
arm_borrow_operation (borrowed from the AArch64 backend) which can
match the comparison type with the required mode and then fixed all
the patterns to use this.  The split patterns that were generating
incorrect modes have all obviously been fixed as well.

The basic rule for the use of a borrow is:
- if the condition code was set by a 'subtract-like' operation (subs, cmp),
  then use CCmode and LTU.
- if the condition code was by unsigned overflow of addition (adds), then
  use CC_Cmode and GEU.

	* config/arm/predicates.md (arm_borrow_operation): New predicate.
	* config/arm/arm.c (subdi3_compare1): Use CCmode for the split.
	(arm_subdi3, subdi_di_zesidi, subdi_di_sesidi): Likewise.
	(subdi_zesidi_zesidi): Likewise.
	(negdi2_compare, negdi2_insn): Likewise.
	(negdi_extensidi): Likewise.
	(negdi_zero_extendsidi): Likewise.
	(arm_cmpdi_insn): Likewise.
	(subsi3_carryin): Use arm_borrow_operation.
	(subsi3_carryin_const): Likewise.
	(subsi3_carryin_const0): Likewise.
	(subsi3_carryin_compare): Likewise.
	(subsi3_carryin_compare_const): Likewise.
	(subsi3_carryin_compare_const0): Likewise.
	(subsi3_carryin_shift): Likewise.
	(rsbsi3_carryin_shift): Likewise.
	(negsi2_carryin_compare): Likewise.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/arm/arm.md
    trunk/gcc/config/arm/predicates.md