[gcc(refs/vendors/ARM/heads/gcs-13)] aarch64: Add GCS instructions

[Szabolcs Nagy <nsz@gcc.gnu.org>]

https://gcc.gnu.org/g:456682d7e40d8c246baed380ffe35645d0516c1d

commit 456682d7e40d8c246baed380ffe35645d0516c1d
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Tue May 9 16:00:01 2023 +0100

    aarch64: Add GCS instructions
    
    Add instructions for the Guarded Control Stack extension.
    
    GCSSS1 and GCSSS2 are modelled as a single GCSSS unspec, because they
    are always used together in the compiler.
    
    Before GCSPOPM and GCSSS2 an extra "mov xn, 0" is added to clear the
    output register, this is needed to get reasonable result when GCS is
    disabled, when the instructions are NOPs. Since the instructions are
    expecetd to be used behind runtime feature checks, this is mainly
    relevant if GCS can be disabled asynchronously.
    
    The output of GCSPOPM is usually not needed, so a separate gcspopm_xzr
    was added to model that. Did not do the same for GCSSS as it is a less
    common operation.
    
    The used mnemonics do not depend on updated assembler since these
    instructions can be used without new -march setting behind a runtime
    check.
    
    Reading the GCSPR is modelled as unspec_volatile so it does not get
    reordered wrt the other instructions changing the GCSPR.
    
    TODO:
    - Do we care about async disable?
    - Do we need GCSSS_xzr? (to avoid the mov x,0)
    
    gcc/ChangeLog:
    
            * config/aarch64/aarch64.md (aarch64_load_gcspr): New.
            (aarch64_gcspopm): New.
            (aarch64_gcspopm_xzr): New.
            (aarch64_gcsss): New.

Diff:
---
 gcc/config/aarch64/aarch64.md | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index de7481bd3c72..b5fcc0239315 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -320,6 +320,9 @@
     UNSPECV_BTI_J		; Represent BTI j.
     UNSPECV_BTI_JC		; Represent BTI jc.
     UNSPECV_CHKFEAT		; Represent CHKFEAT X16.
+    UNSPECV_GCSPR		; Represent MRS Xn, GCSPR_EL0
+    UNSPECV_GCSPOPM		; Represent GCSPOPM.
+    UNSPECV_GCSSS		; Represent GCSSS1 and GCSSS2.
     UNSPECV_TSTART		; Represent transaction start.
     UNSPECV_TCOMMIT		; Represent transaction commit.
     UNSPECV_TCANCEL		; Represent transaction cancel.
@@ -7906,6 +7909,38 @@
   "hint\\t40 // chkfeat x16"
 )
 
+;; Guarded Control Stack (GCS) instructions
+(define_insn "aarch64_load_gcspr"
+  [(set (match_operand:DI 0 "register_operand" "=r")
+	(unspec_volatile:DI [(const_int 0)] UNSPECV_GCSPR))]
+  ""
+  "mrs\\t%0, s3_3_c2_c5_1 // gcspr_el0"
+  [(set_attr "type" "mrs")]
+)
+
+(define_insn "aarch64_gcspopm"
+  [(set (match_operand:DI 0 "register_operand" "=r")
+	(unspec_volatile:DI [(const_int 0)] UNSPECV_GCSPOPM))]
+  ""
+  "mov\\t%0, 0\;sysl\\t%0, #3, c7, c7, #1 // gcspopm"
+  [(set_attr "length" "8")]
+)
+
+(define_insn "aarch64_gcspopm_xzr"
+  [(unspec_volatile [(const_int 0)] UNSPECV_GCSPOPM)]
+  ""
+  "sysl\\txzr, #3, c7, c7, #1 // gcspopm"
+)
+
+(define_insn "aarch64_gcsss"
+  [(set (match_operand:DI 0 "register_operand" "=r")
+	(unspec_volatile:DI [(match_operand:DI 1 "register_operand" "r")]
+	  UNSPECV_GCSSS))]
+  ""
+  "sys\\t#3, c7, c7, #2, %1 // gcsss1\;mov\\t%0, 0\;sysl\\t%0, #3, c7, c7, #3 // gcsss2"
+  [(set_attr "length" "12")]
+)
+
 ;; AdvSIMD Stuff
 (include "aarch64-simd.md")