[gcc r13-4032] riscv: bitmanip: add orc.b as an unspec

[Philipp Tomsich <ptomsich@gcc.gnu.org>]

https://gcc.gnu.org/g:eab3d2d17dd8fedc856cf175a3f2174770ecb64d

commit r13-4032-geab3d2d17dd8fedc856cf175a3f2174770ecb64d
Author: Philipp Tomsich <philipp.tomsich@vrull.eu>
Date:   Thu May 27 17:20:05 2021 +0200

    riscv: bitmanip: add orc.b as an unspec
    
    As a basis for optimized string functions (e.g., the by-pieces
    implementations), we need orc.b available.  This adds orc.b as an
    unspec, so we can expand to it.
    
    gcc/ChangeLog:
    
            * config/riscv/bitmanip.md (orcb<mode>2): Add orc.b as an
              unspec.
            * config/riscv/riscv.md: Add UNSPEC_ORC_B.
    
    Signed-off-by: Philipp Tomsich <philipp.tomsich@vrull.eu>

Diff:
---
 gcc/config/riscv/bitmanip.md | 8 ++++++++
 gcc/config/riscv/riscv.md    | 3 +++
 2 files changed, 11 insertions(+)

diff --git a/gcc/config/riscv/bitmanip.md b/gcc/config/riscv/bitmanip.md
index d26f3567182..48c249f2a68 100644
--- a/gcc/config/riscv/bitmanip.md
+++ b/gcc/config/riscv/bitmanip.md
@@ -255,6 +255,14 @@
   "rolw\t%0,%1,%2"
   [(set_attr "type" "bitmanip")])
 
+;; orc.b (or-combine) is added as an unspec for the benefit of the support
+;; for optimized string functions (such as strcmp).
+(define_insn "orcb<mode>2"
+  [(set (match_operand:X 0 "register_operand" "=r")
+	(unspec:X [(match_operand:X 1 "register_operand" "r")] UNSPEC_ORC_B))]
+  "TARGET_ZBB"
+  "orc.b\t%0,%1")
+
 (define_insn "bswap<mode>2"
   [(set (match_operand:X 0 "register_operand" "=r")
         (bswap:X (match_operand:X 1 "register_operand" "r")))]
diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
index 798f7370a08..532289dd178 100644
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -62,6 +62,9 @@
 
   ;; Stack tie
   UNSPEC_TIE
+
+  ;; OR-COMBINE
+  UNSPEC_ORC_B
 ])
 
 (define_c_enum "unspecv" [