Add codegen option for branch protection and pointer authentication on AArch64

The branch-protection codegen option enables the use of hint-space pointer
authentication code for AArch64 targets

compiler/rustc_session/src/config.rs

@@ -842,6 +842,30 @@ impl Passes {
     }
 }
 
+#[derive(Clone, Copy, Hash, Debug, PartialEq)]
+pub enum PAuthKey {
+    A,
+    B,
+}
+
+#[derive(Clone, Copy, Hash, Debug, PartialEq)]
+pub struct PacRet {
+    pub leaf: bool,
+    pub key: PAuthKey,
+}
+
+#[derive(Clone, Copy, Hash, Debug, PartialEq)]
+pub struct BranchProtection {
+    pub bti: bool,
+    pub pac_ret: Option<PacRet>,
+}
+
+impl Default for BranchProtection {
+    fn default() -> Self {
+        BranchProtection { bti: false, pac_ret: None }
+    }
+}
+
 pub const fn default_lib_output() -> CrateType {
     CrateType::Rlib
 }
@@ -2487,9 +2511,9 @@ impl PpMode {
 crate mod dep_tracking {
     use super::LdImpl;
     use super::{
-        CFGuard, CrateType, DebugInfo, ErrorOutputType, InstrumentCoverage, LinkerPluginLto,
-        LocationDetail, LtoCli, OptLevel, OutputType, OutputTypes, Passes, SourceFileHashAlgorithm,
-        SwitchWithOptPath, SymbolManglingVersion, TrimmedDefPaths,
+        BranchProtection, CFGuard, CrateType, DebugInfo, ErrorOutputType, InstrumentCoverage,
+        LinkerPluginLto, LocationDetail, LtoCli, OptLevel, OutputType, OutputTypes, Passes,
+        SourceFileHashAlgorithm, SwitchWithOptPath, SymbolManglingVersion, TrimmedDefPaths,
     };
     use crate::lint;
     use crate::options::WasiExecModel;
@@ -2583,6 +2607,7 @@ crate mod dep_tracking {
         OutputType,
         RealFileName,
         LocationDetail,
+        BranchProtection,
     );
 
     impl<T1, T2> DepTrackingHash for (T1, T2)

compiler/rustc_session/src/options.rs

@@ -389,6 +389,8 @@ mod desc {
     pub const parse_gcc_ld: &str = "one of: no value, `lld`";
     pub const parse_stack_protector: &str =
         "one of (`none` (default), `basic`, `strong`, or `all`)";
+    pub const parse_branch_protection: &str =
+        "a `+` separated combination of `bti`, `b-key`, `pac-ret`, or `leaf`";
 }
 
 mod parse {
@@ -929,6 +931,33 @@ mod parse {
         }
         true
     }
+
+    crate fn parse_branch_protection(slot: &mut BranchProtection, v: Option<&str>) -> bool {
+        match v {
+            Some(s) => {
+                for opt in s.split('+') {
+                    match opt {
+                        "bti" => slot.bti = true,
+                        "pac-ret" if slot.pac_ret.is_none() => {
+                            slot.pac_ret = Some(PacRet { leaf: false, key: PAuthKey::A })
+                        }
+                        "leaf" => match slot.pac_ret.as_mut() {
+                            Some(pac) => pac.leaf = true,
+                            _ => return false,
+                        },
+                        "b-key" => match slot.pac_ret.as_mut() {
+                            Some(pac) => pac.key = PAuthKey::B,
+                            _ => return false,
+                        },
+                        _ => return false,
+                    };
+                }
+            }
+
+            _ => return false,
+        }
+        true
+    }
 }
 
 options! {
@@ -942,6 +971,8 @@ options! {
 
     ar: String = (String::new(), parse_string, [UNTRACKED],
         "this option is deprecated and does nothing"),
+    branch_protection: BranchProtection = (BranchProtection::default(), parse_branch_protection, [TRACKED],
+        "set options for branch target identification and pointer authentication on AArch64"),
     code_model: Option<CodeModel> = (None, parse_code_model, [TRACKED],
         "choose the code model to use (`rustc --print code-models` for details)"),
     codegen_units: Option<usize> = (None, parse_opt_number, [UNTRACKED],