[arm] Add alternative canonicalizations for subtract-with-carry + shift
authorRichard Earnshaw <rearnsha@arm.com>
Fri, 18 Oct 2019 19:03:19 +0000 (19:03 +0000)
committerRichard Earnshaw <rearnsha@gcc.gnu.org>
Fri, 18 Oct 2019 19:03:19 +0000 (19:03 +0000)
commit0b478cddf9e95406cd865c94bf99705ec8acddde
treee4aea46ee82842c8dc421bca46b1c22e20ade936
parentf6ff841bc8dd87ce364deb217dc6d1ec5dc31de8
[arm] Add alternative canonicalizations for subtract-with-carry + shift

This patch adds a couple of alternative canonicalizations to allow
combine to match a subtract-with-carry operation when one of the operands
is shifted first.  The most common case of this is when combining a
sign-extend of one operand with a long-long value during subtraction.
The RSC variant is only enabled for Arm, the SBC variant for any 32-bit
compilation.

* config/arm/arm.md (subsi3_carryin_shift_alt): New pattern.
(rsbsi3_carryin_shift_alt): Likewise.

From-SVN: r277176
gcc/ChangeLog
gcc/config/arm/arm.md