[clang][AARCH64] Add __ARM_FEATURE_{PAC, BTI}_DEFAULT defines

[tamas.petz]

Summary

As defined by Arm C Language Extensions (ACLE) these macro defines
should be set to specific values depending on -mbranch-protection.

[tamas.petz]

Depends on: https://reviews.llvm.org/D77131

[chill]

LGTM, conditional on the dependent patch. Thanks!

clang/include/clang/Basic/LangOptions.h

#include "clang/Basic/LangOptions.def"
   }
 
   bool assumeFunctionsAreConvergent() const {
     return ConvergentFunctions;
   }
 
   /// Return the OpenCL C or C++ version as a VersionTuple.
   VersionTuple getOpenCLVersionTuple() const;
+
+  /// Check if return address signing is enabled.
+  bool hasSignReturnAddress() const {
+    return getSignReturnAddressScope() != SignReturnAddressScopeKind::None;
+  }
+
+  /// Check if return address signing uses AKey.
+  bool isSignReturnAddressWithAKey() const {
+    return getSignReturnAddressKey() == SignReturnAddressKeyKind::AKey;
+  }
+
+  /// Check if leaf functions are also signed.
+  bool isSignReturnAddressScopeAll() const {
+    return getSignReturnAddressScope() == SignReturnAddressScopeKind::All;
+  }
 };
 
 /// Floating point control options
 class FPOptions {
 public:
   FPOptions() : fp_contract(LangOptions::FPC_Off),
                 fenv_access(LangOptions::FEA_Off),
                 rounding(LangOptions::FPR_ToNearest),

clang/lib/Basic/Targets/AArch64.cpp

if (HasMTE)
     Builder.defineMacro("__ARM_FEATURE_MEMORY_TAGGING", "1");
 
   if (HasTME)
     Builder.defineMacro("__ARM_FEATURE_TME", "1");
 
   if ((FPU & NeonMode) && HasFP16FML)
     Builder.defineMacro("__ARM_FEATURE_FP16FML", "1");
 
+  if (Opts.hasSignReturnAddress()) {
+    // Bitmask:
+    // 0: Protection using the A key
+    // 1: Protection using the B key
+    // 2: Protection including leaf functions
+    unsigned Value = 0;
+
+    if (Opts.isSignReturnAddressWithAKey())
+      Value |= (1 << 0);
+    else
+      Value |= (1 << 1);
+
+    if (Opts.isSignReturnAddressScopeAll())
+      Value |= (1 << 2);
+
+    Builder.defineMacro("__ARM_FEATURE_PAC_DEFAULT", std::to_string(Value));
+  }
+
+  if (Opts.BranchTargetEnforcement)
+    Builder.defineMacro("__ARM_FEATURE_BTI_DEFAULT", "1");
+
   switch (ArchKind) {
   default:
     break;
   case llvm::AArch64::ArchKind::ARMV8_1A:
     getTargetDefinesARMV81A(Opts, Builder);
     break;
   case llvm::AArch64::ArchKind::ARMV8_2A:
     getTargetDefinesARMV82A(Opts, Builder);

clang/test/Preprocessor/aarch64-target-features.c

 // CHECK: __ARM_NEON_FP 0xE
 // CHECK: __ARM_PCS_AAPCS64 1
 // CHECK-NOT: __ARM_PCS 1
 // CHECK-NOT: __ARM_PCS_VFP 1
 // CHECK-NOT: __ARM_SIZEOF_MINIMAL_ENUM 1
 // CHECK-NOT: __ARM_SIZEOF_WCHAR_T 2
 // CHECK-NOT: __ARM_FEATURE_SVE
 // CHECK-NOT: __ARM_FEATURE_DOTPROD
+// CHECK-NOT: __ARM_FEATURE_PAC_DEFAULT
+// CHECK-NOT: __ARM_FEATURE_BTI_DEFAULT
 
 // RUN: %clang -target aarch64-none-linux-gnu -march=armv8-a+crypto -x c -E -dM %s -o - | FileCheck --check-prefix=CHECK-CRYPTO %s
 // RUN: %clang -target arm64-none-linux-gnu -march=armv8-a+crypto -x c -E -dM %s -o - | FileCheck --check-prefix=CHECK-CRYPTO %s
 // CHECK-CRYPTO: __ARM_FEATURE_CRYPTO 1
 
 // RUN: %clang -target aarch64-none-linux-gnu -mcrc -x c -E -dM %s -o - | FileCheck --check-prefix=CHECK-CRC32 %s
 // RUN: %clang -target arm64-none-linux-gnu -mcrc -x c -E -dM %s -o - | FileCheck --check-prefix=CHECK-CRC32 %s
 // RUN: %clang -target aarch64-none-linux-gnu -march=armv8-a+crc -x c -E -dM %s -o - | FileCheck --check-prefix=CHECK-CRC32 %s

 // RUN: %clang -target aarch64 -march=armv8.1a+noSIMD -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-V81A-FEATURE-3 %s
 // CHECK-V81A-FEATURE-1: "-cc1"{{.*}} "-triple" "aarch64{{.*}}" "-target-feature" "+neon" "-target-feature" "+v8.1a" "-target-feature" "+crypto"
 // CHECK-V81A-FEATURE-2: "-cc1"{{.*}} "-triple" "aarch64{{.*}}" "-target-feature" "+neon" "-target-feature" "+v8.1a" "-target-feature" "-crypto"
 // CHECK-V81A-FEATURE-3: "-cc1"{{.*}} "-triple" "aarch64{{.*}}" "-target-feature" "+v8.1a" "-target-feature" "-neon"
 
 // ================== Check Memory Tagging Extensions (MTE).
 // RUN: %clang -target arm64-none-linux-gnu -march=armv8.5-a+memtag -x c -E -dM %s -o - 2>&1 | FileCheck -check-prefix=CHECK-MEMTAG %s
 // CHECK-MEMTAG: __ARM_FEATURE_MEMORY_TAGGING 1
+
+// ================== Check Pointer Authentication Extension (PAuth).
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH-OFF %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8.5-a -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH-OFF %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=none -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH-OFF %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=bti -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH-OFF %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=standard -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=pac-ret -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=pac-ret+b-key -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH-BKEY %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=pac-ret+leaf -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH-ALL %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=pac-ret+leaf+b-key -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH-BKEY-ALL %s
+// CHECK-PAUTH-OFF-NOT:  __ARM_FEATURE_PAC_DEFAULT
+// CHECK-PAUTH:          #define __ARM_FEATURE_PAC_DEFAULT 1
+// CHECK-PAUTH-BKEY:     #define __ARM_FEATURE_PAC_DEFAULT 2
+// CHECK-PAUTH-ALL:      #define __ARM_FEATURE_PAC_DEFAULT 5
+// CHECK-PAUTH-BKEY-ALL: #define __ARM_FEATURE_PAC_DEFAULT 6
+
+// ================== Check Branch Target Identification (BTI).
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-BTI-OFF %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8.5-a -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-BTI-OFF %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=none -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-BTI-OFF %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=pac-ret -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-BTI-OFF %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=pac-ret+leaf -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-BTI-OFF %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=pac-ret+b-key -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-BTI-OFF %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=pac-ret+leaf+b-key -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-BTI-OFF %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=standard -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-BTI %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=bti -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-BTI %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -mbranch-protection=pac-ret+bti -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-BTI %s
+// CHECK-BTI-OFF-NOT: __ARM_FEATURE_BTI_DEFAULT
+// CHECK-BTI:         #define __ARM_FEATURE_BTI_DEFAULT 1