[ARM][clang] Define feature test macro for the PACBTI-M extension

[stuij]

Summary

If the extension string "+pacbti" was given in -march=... or -mcpu=... options the compiler shall define the following preprocessor macros:

__ARM_FEATURE_PAUTH with value 1.
__ARM_FEATURE_BTI with value 1.

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:

• Momchil Velikov
• Ties Stuij

[miyuki]

clang/lib/Basic/Targets/ARM.cpp

897

Since we decided to have two separate flags, I think this line should be in a separate if statement: if (HasBTI).

[chill]

clang/lib/Basic/Targets/ARM.cpp

897

Agree. If this ever changes, we'd have to modify only around lines 550.

[stuij]

addressing review comment

[stuij]

reuploading after rebase to resolve patch apply failure

clang/lib/Basic/Targets/ARM.h

 //===--- ARM.h - Declare ARM target feature support -------------*- C++ -*-===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
class LLVM_LIBRARY_VISIBILITY ARMTargetInfo : public TargetInfo {
   unsigned CRC : 1;
   unsigned Crypto : 1;
   unsigned SHA2 : 1;
   unsigned AES : 1;
   unsigned DSP : 1;
   unsigned Unaligned : 1;
   unsigned DotProd : 1;
   unsigned HasMatMul : 1;
+  unsigned HasPAC : 1;
+  unsigned HasBTI : 1;
 
   enum {
     LDREX_B = (1 << 0), /// byte (8-bit)
     LDREX_H = (1 << 1), /// half (16-bit)
     LDREX_W = (1 << 2), /// word (32-bit)
     LDREX_D = (1 << 3), /// double (64-bit)
   };
 

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
 //
 //===----------------------------------------------------------------------===//
 //
bool ARMTargetInfo::handleTargetFeatures(std::vector<std::string> &Features,
   AES = 0;
   DSP = 0;
   Unaligned = 1;
   SoftFloat = false;
   // Note that SoftFloatABI is initialized in our constructor.
   HWDiv = 0;
   DotProd = 0;
   HasMatMul = 0;
+  HasPAC = 0;
+  HasBTI = 0;
   HasFloat16 = true;
   ARMCDECoprocMask = 0;
   HasBFloat16 = false;
 
   // This does not diagnose illegal cases like having both
   // "+vfpv2" and "+vfpv3" or having "+neon" and "-fp64".
   for (const auto &Feature : Features) {
     if (Feature == "+soft-float") {
for (const auto &Feature : Features) {
     } else if (Feature == "+i8mm") {
       HasMatMul = 1;
     } else if (Feature.size() == strlen("+cdecp0") && Feature >= "+cdecp0" &&
                Feature <= "+cdecp7") {
       unsigned Coproc = Feature.back() - '0';
       ARMCDECoprocMask |= (1U << Coproc);
     } else if (Feature == "+bf16") {
       HasBFloat16 = true;
+    } else if (Feature == "+pacbti") {
+      HasPAC = 1;
+      HasBTI = 1;
     }
   }
 
   switch (ArchVersion) {
   case 6:
     if (ArchProfile == llvm::ARM::ProfileKind::M)
       LDREX = 0;
     else if (ArchKind == llvm::ARM::ArchKind::ARMV6K)
void ARMTargetInfo::getTargetDefines(const LangOptions &Opts,
 
   // Armv8.2-A dot product intrinsics
   if (DotProd)
     Builder.defineMacro("__ARM_FEATURE_DOTPROD", "1");
 
   if (HasMatMul)
     Builder.defineMacro("__ARM_FEATURE_MATMUL_INT8", "1");
 
+  if (HasPAC) {
+    Builder.defineMacro("__ARM_FEATURE_PAUTH", "1");
+    Builder.defineMacro("__ARM_FEATURE_BTI", "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");

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

 // 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
 
+// RUN: %clang -target arm-arm-none-eabi -march=armv8.1-m.main -x c -E -dM %s -o - | FileCheck --check-prefixes=CHECK-NOBTI-EXT,CHECK-NOPAC-EXT %s
+// RUN: %clang -target arm-arm-none-eabi -march=armv7-m+pacbti -x c -E -dM %s -o - | FileCheck --check-prefixes=CHECK-PACBTI-EXT %s
+// CHECK-NOBTI-EXT-NOT: #define __ARM_FEATURE_BTI 1
+// CHECK-NOPAC-EXT-NOT: #define __ARM_FEATURE_PAUTH 1
+// CHECK-PACBTI-EXT: #define __ARM_FEATURE_BTI 1
+// CHECK-PACBTI-EXT: #define __ARM_FEATURE_PAUTH 1
+
 // ================== 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