[arm] Correct cost calculations involving borrow for subtracts.
authorRichard Earnshaw <rearnsha@arm.com>
Fri, 18 Oct 2019 19:02:50 +0000 (19:02 +0000)
committerRichard Earnshaw <rearnsha@gcc.gnu.org>
Fri, 18 Oct 2019 19:02:50 +0000 (19:02 +0000)
commitbbead5babc046279d886b059e68e613b0185b2ff
tree124a99d80876a893377cb89eb847f09c6eca55f6
parent0a67306e3cc2adfe0ef2fe313a86f57141ab57b2
[arm] Correct cost calculations involving borrow for subtracts.

The rtx_cost calculations when a borrow operation was being performed were
not being calculated correctly.  The borrow is free as part of the
subtract-with-carry instructions.  This patch recognizes the various
idioms that can describe this and returns the correct costs.

* config/arm/arm.c (arm_rtx_costs_internal, case MINUS): Handle
borrow operations.

From-SVN: r277173
gcc/ChangeLog
gcc/config/arm/arm.c