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

2 files changed, 27 insertions, 0 deletions

diff --git a/clang/lib/Basic/Targets/AArch64.cpp b/clang/lib/Basic/Targets/AArch64.cpp
index bdfb5700b46..5214f7c30ee 100644
--- a/clang/lib/Basic/Targets/AArch64.cpp
+++ b/clang/lib/Basic/Targets/AArch64.cpp
@@ -15,6 +15,8 @@
 #include "clang/Basic/TargetInfo.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/Support/AArch64TargetParser.h"
 
 using namespace clang;
 using namespace clang::targets;
@@ -107,6 +109,28 @@ bool AArch64TargetInfo::setABI(const std::string &Name) {
   return true;
 }
 
+bool AArch64TargetInfo::validateBranchProtection(StringRef Spec,
+                                                 BranchProtectionInfo &BPI,
+                                                 StringRef &Err) const {
+  llvm::AArch64::ParsedBranchProtection PBP;
+  if (!llvm::AArch64::parseBranchProtection(Spec, PBP, Err))
+    return false;
+
+  BPI.SignReturnAddr =
+      llvm::StringSwitch<CodeGenOptions::SignReturnAddressScope>(PBP.Scope)
+          .Case("non-leaf", CodeGenOptions::SignReturnAddressScope::NonLeaf)
+          .Case("all", CodeGenOptions::SignReturnAddressScope::All)
+          .Default(CodeGenOptions::SignReturnAddressScope::None);
+
+  if (PBP.Key == "a_key")
+    BPI.SignKey = CodeGenOptions::SignReturnAddressKeyValue::AKey;
+  else
+    BPI.SignKey = CodeGenOptions::SignReturnAddressKeyValue::BKey;
+
+  BPI.BranchTargetEnforcement = PBP.BranchTargetEnforcement;
+  return true;
+}
+
 bool AArch64TargetInfo::isValidCPUName(StringRef Name) const {
   return Name == "generic" ||
          llvm::AArch64::parseCPUArch(Name) != llvm::AArch64::ArchKind::INVALID;
diff --git a/clang/lib/Basic/Targets/AArch64.h b/clang/lib/Basic/Targets/AArch64.h
index 7062ea1ae50..5e78237743c 100644
--- a/clang/lib/Basic/Targets/AArch64.h
+++ b/clang/lib/Basic/Targets/AArch64.h
@@ -49,6 +49,9 @@ public:
   StringRef getABI() const override;
   bool setABI(const std::string &Name) override;
 
+  bool validateBranchProtection(StringRef, BranchProtectionInfo &,
+                                StringRef &) const override;
+
   bool isValidCPUName(StringRef Name) const override;
   void fillValidCPUList(SmallVectorImpl<StringRef> &Values) const override;
   bool setCPU(const std::string &Name) override;