[clang][ARM] emit PACBTI-M feature defines

[stuij]

Summary

emit ARM_FEATURE_BTI_DEFAULT and ARM_FEATURE_PAC_DEFAULT defines when those
features have been enabled

This patch is part of a series that adds support for the PACBTI-M extension of
the Armv8.1-M architecture, as detailed here:

https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/armv8-1-m-pointer-authentication-and-branch-target-identification-extension

The PACBTI-M specification can be found in the Armv8-M Architecture Reference
Manual:

https://developer.arm.com/documentation/ddi0553/latest

The following people contributed to this patch:

• Victor Campos
• Ties Stuij

[ostannard]

LGTM, I assume that the pre-commit test failure is because the bot hasn't applied the parent patches.

[stuij]

obeying clang-format

clang/lib/Basic/Targets/ARM.cpp

 //===--- ARM.cpp - Implement ARM target feature support -------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
if (HasMatMul)
     Builder.defineMacro("__ARM_FEATURE_MATMUL_INT8", "1");
 
   if (HasBFloat16) {
     Builder.defineMacro("__ARM_FEATURE_BF16", "1");
     Builder.defineMacro("__ARM_FEATURE_BF16_VECTOR_ARITHMETIC", "1");
     Builder.defineMacro("__ARM_BF16_FORMAT_ALTERNATIVE", "1");
   }
 
+  if (Opts.BranchTargetEnforcement)
+    Builder.defineMacro("__ARM_FEATURE_BTI_DEFAULT", "1");
+
+  if (Opts.hasSignReturnAddress()) {
+    unsigned Value = Opts.isSignReturnAddressWithAKey() ? 1 : 2;
+    if (Opts.isSignReturnAddressScopeAll())
+      Value |= 1 << 2;
+    Builder.defineMacro("__ARM_FEATURE_PAC_DEFAULT", Twine(Value));
+  }
+
   switch (ArchKind) {
   default:
     break;
   case llvm::ARM::ArchKind::ARMV8_1A:
     getTargetDefinesARMV81A(Opts, Builder);
     break;
   case llvm::ARM::ArchKind::ARMV8_2A:
     getTargetDefinesARMV82A(Opts, Builder);

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

 // RUN: %clang -target armv9.2a-none-none-eabi -x c -E -dM %s -o - | FileCheck -match-full-lines --check-prefix=CHECK-V92A %s
 // CHECK-V92A: #define __ARM_ARCH 9
 // CHECK-V92A: #define __ARM_ARCH_9_2A__ 1
 // CHECK-V92A: #define __ARM_ARCH_PROFILE 'A'
 
 // RUN: %clang -target arm-none-none-eabi -march=armv7-m -mfpu=softvfp -x c -E -dM %s -o - | FileCheck --check-prefix=CHECK-SOFTVFP %s
 // CHECK-SOFTVFP-NOT: #define __ARM_FP 0x
 
+// Test Armv8.1-M PACBTI
+// RUN: %clang -target arm-arm-none-eabi -march=armv8.1-m.main -x c -E -dM %s -o - | FileCheck --check-prefixes=CHECK-NOBTI,CHECK-NOPAC %s
+// RUN: %clang -target arm-arm-none-eabi -march=armv8.1-m.main -mbranch-protection=bti -x c -E -dM %s -o - | FileCheck --check-prefixes=CHECK-BTI,CHECK-NOPAC %s
+// RUN: %clang -target arm-arm-none-eabi -march=armv8.1-m.main -mbranch-protection=pac-ret -x c -E -dM %s -o - | FileCheck --check-prefixes=CHECK-PAC,CHECK-NOBTI %s
+// RUN: %clang -target arm-arm-none-eabi -march=armv8.1-m.main -mbranch-protection=pac-ret+b-key -x c -E -dM %s -o - | FileCheck --check-prefixes=CHECK-PAC-BKEY,CHECK-NOBTI %s
+// RUN: %clang -target arm-arm-none-eabi -march=armv8.1-m.main -mbranch-protection=pac-ret+leaf -x c -E -dM %s -o - | FileCheck --check-prefixes=CHECK-PAC-LEAF,CHECK-NOBTI %s
+// RUN: %clang -target arm-arm-none-eabi -march=armv8.1-m.main -mbranch-protection=pac-ret+b-key+leaf -x c -E -dM %s -o - | FileCheck --check-prefixes=CHECK-PAC-BKEY-LEAF,CHECK-NOBTI %s
+// RUN: %clang -target arm-arm-none-eabi -march=armv8.1-m.main -mbranch-protection=bti+pac-ret -x c -E -dM %s -o - | FileCheck --check-prefixes=CHECK-PAC,CHECK-BTI %s
+// RUN: %clang -target arm-arm-none-eabi -march=armv8.1-m.main -mbranch-protection=bti+pac-ret+b-key -x c -E -dM %s -o - | FileCheck --check-prefixes=CHECK-PAC-BKEY,CHECK-BTI %s
+// RUN: %clang -target arm-arm-none-eabi -march=armv8.1-m.main -mbranch-protection=bti+pac-ret+leaf -x c -E -dM %s -o - | FileCheck --check-prefixes=CHECK-PAC-LEAF,CHECK-BTI %s
+// RUN: %clang -target arm-arm-none-eabi -march=armv8.1-m.main -mbranch-protection=bti+pac-ret+b-key+leaf -x c -E -dM %s -o - | FileCheck --check-prefixes=CHECK-PAC-BKEY-LEAF,CHECK-BTI %s
+// CHECK-NOBTI-NOT: #define __ARM_FEATURE_BTI_DEFAULT
+// CHECK-NOPAC-NOT: #define __ARM_FEATURE_PAC_DEFAULT
+// CHECK-BTI: #define __ARM_FEATURE_BTI_DEFAULT 1
+// CHECK-PAC: #define __ARM_FEATURE_PAC_DEFAULT 1
+// CHECK-PAC-BKEY: #define __ARM_FEATURE_PAC_DEFAULT 2
+// CHECK-PAC-LEAF: #define __ARM_FEATURE_PAC_DEFAULT 5
+// CHECK-PAC-BKEY-LEAF: #define __ARM_FEATURE_PAC_DEFAULT 6
+
 // ================== Check BFloat16 Extensions.
 // RUN: %clang -target arm-arm-none-eabi -march=armv8.6-a+bf16 -x c -E -dM %s -o - 2>&1 | FileCheck -check-prefix=CHECK-BFLOAT %s
 // CHECK-BFLOAT: #define __ARM_BF16_FORMAT_ALTERNATIVE 1
 // CHECK-BFLOAT: #define __ARM_FEATURE_BF16 1
 // CHECK-BFLOAT: #define __ARM_FEATURE_BF16_VECTOR_ARITHMETIC 1
 
 // Check crypto feature test macros
 // RUN: %clang -target arm-arm-none-eabi -march=armv8-a+crypto -x c -E -dM %s -o - | FileCheck -match-full-lines --check-prefix=CHECK-CRYPTO %s