Implement target(branch-protection) attribute for AArch64
This patch implements `__attribute__((target("branch-protection=...")))`
in a manner, compatible with the analogous GCC feature:
https://gcc.gnu.org/onlinedocs/gcc-9.2.0/gcc/AArch64-Function-Attributes.html#AArch64-Function-Attributes
Differential Revision: https://reviews.llvm.org/D68711
diff --git a/llvm/lib/Support/AArch64TargetParser.cpp b/llvm/lib/Support/AArch64TargetParser.cpp
index 6f1d6d5..b5cd4af 100644
--- a/llvm/lib/Support/AArch64TargetParser.cpp
+++ b/llvm/lib/Support/AArch64TargetParser.cpp
@@ -213,3 +213,51 @@
}
return ArchKind::INVALID;
}
+
+// Parse a branch protection specification, which has the form
+// standard | none | [bti,pac-ret[+b-key,+leaf]*]
+// Returns true on success, with individual elements of the specification
+// returned in `PBP`. Returns false in error, with `Err` containing
+// an erroneous part of the spec.
+bool AArch64::parseBranchProtection(StringRef Spec, ParsedBranchProtection &PBP,
+ StringRef &Err) {
+ PBP = {"none", "a_key", false};
+ if (Spec == "none")
+ return true; // defaults are ok
+
+ if (Spec == "standard") {
+ PBP.Scope = "non-leaf";
+ PBP.BranchTargetEnforcement = true;
+ return true;
+ }
+
+ SmallVector<StringRef, 4> Opts;
+ Spec.split(Opts, "+");
+ for (int I = 0, E = Opts.size(); I != E; ++I) {
+ StringRef Opt = Opts[I].trim();
+ if (Opt == "bti") {
+ PBP.BranchTargetEnforcement = true;
+ continue;
+ }
+ if (Opt == "pac-ret") {
+ PBP.Scope = "non-leaf";
+ for (; I + 1 != E; ++I) {
+ StringRef PACOpt = Opts[I + 1].trim();
+ if (PACOpt == "leaf")
+ PBP.Scope = "all";
+ else if (PACOpt == "b-key")
+ PBP.Key = "b_key";
+ else
+ break;
+ }
+ continue;
+ }
+ if (Opt == "")
+ Err = "<empty>";
+ else
+ Err = Opt;
+ return false;
+ }
+
+ return true;
+}