[ARM][Driver] Ensure NEON is enabled and Disabled correctly

In llvm#130623 support was added for `+nosimd` in the clang driver.
Following this PR, it was discovered that, if NEONS is disabled in
the command line, it did not disable features that have NEON as
a requirement, such as Crypto or AES. To achieve this, clang will
now check if SIMD has been disabled when using a NEON supported
FPU. If this is the case, it will disable all features that depend
on NEON.

While working on this Patch, I spotted that for features that rely
on NEON, when used, do not enable NEON in the Driver. This meant
that when using AES for example, NEON would not be activated. NEON
is required when using features such as AES, so this is now enabled
when using such features.

Author: Stylie777

clang/docs/ReleaseNotes.rst

@@ -601,6 +601,8 @@ Arm and AArch64 Support
 - The ``+nosimd`` attribute is now fully supported for ARM. Previously, this had no effect when being used with
   ARM targets, however this will now disable NEON instructions being generated. The ``simd`` option is
   also now printed when the ``--print-supported-extensions`` option is used.
+- NEON is correctly enabled when using features that depend on NEON , and disables all features that depend on
+  NEON when using ``+nosimd``.
 
 -  Support for __ptrauth type qualifier has been added.
 

clang/lib/Driver/ToolChains/Arch/ARM.cpp

@@ -781,6 +781,30 @@ llvm::ARM::FPUKind arm::getARMTargetFeatures(const Driver &D,
   if (FPUKind == llvm::ARM::FK_FPV5_D16 || FPUKind == llvm::ARM::FK_FPV5_SP_D16)
     Features.push_back("-mve.fp");
 
+  // If SIMD has been disabled and the selected FPU support NEON, then features
+  // that rely on NEON Instructions should also be disabled. Cases where NEON
+  // needs activating to support another feature is handled below with the
+  // crypto feature.
+  bool HasSimd = false;
+  const auto ItSimd =
+  llvm::find_if(llvm::reverse(Features), [](const StringRef F) {
+    return F.contains("neon");
+  });
+  const bool FoundSimd = ItSimd != Features.rend();
+  const bool FPUSupportsNeon =
+    (llvm::ARM::FPUNames[FPUKind].NeonSupport == llvm::ARM::NeonSupportLevel::Neon) ||
+    (llvm::ARM::FPUNames[FPUKind].NeonSupport == llvm::ARM::NeonSupportLevel::Crypto);
+  if(FoundSimd)
+  HasSimd = ItSimd->take_front() == "+";
+  if(!HasSimd && FPUSupportsNeon) {
+    Features.push_back("-sha2");
+    Features.push_back("-aes");
+    Features.push_back("-crypto");
+    Features.push_back("-dotprod");
+    Features.push_back("-bf16");
+    Features.push_back("-imm8");
+  }
+
   // For Arch >= ARMv8.0 && A or R profile:  crypto = sha2 + aes
   // Rather than replace within the feature vector, determine whether each
   // algorithm is enabled and append this to the end of the vector.
@@ -791,6 +815,9 @@ llvm::ARM::FPUKind arm::getARMTargetFeatures(const Driver &D,
   // FIXME: this needs reimplementation after the TargetParser rewrite
   bool HasSHA2 = false;
   bool HasAES = false;
+  bool HasBF16 = false;
+  bool HasDotprod = false;
+  bool HasI8MM = false;
   const auto ItCrypto =
       llvm::find_if(llvm::reverse(Features), [](const StringRef F) {
         return F.contains("crypto");
@@ -803,12 +830,28 @@ llvm::ARM::FPUKind arm::getARMTargetFeatures(const Driver &D,
       llvm::find_if(llvm::reverse(Features), [](const StringRef F) {
         return F.contains("crypto") || F.contains("aes");
       });
-  const bool FoundSHA2 = ItSHA2 != Features.rend();
-  const bool FoundAES = ItAES != Features.rend();
-  if (FoundSHA2)
+  const auto ItBF16 =
+      llvm::find_if(llvm::reverse(Features), [](const StringRef F) {
+        return F.contains("bf16");
+      });
+  const auto ItDotprod =
+      llvm::find_if(llvm::reverse(Features), [](const StringRef F) {
+        return F.contains("dotprod");
+      });
+  const auto ItI8MM =
+      llvm::find_if(llvm::reverse(Features), [](const StringRef F) {
+        return F.contains("i8mm");
+      });
+  if (ItSHA2 != Features.rend())
     HasSHA2 = ItSHA2->take_front() == "+";
-  if (FoundAES)
+  if (ItAES != Features.rend())
     HasAES = ItAES->take_front() == "+";
+  if (ItBF16 != Features.rend())
+    HasBF16 = ItBF16->take_front() == "+";
+  if (ItDotprod != Features.rend())
+    HasDotprod = ItDotprod->take_front() == "+";
+  if (ItI8MM != Features.rend())
+    HasI8MM = ItI8MM->take_front() == "+";
   if (ItCrypto != Features.rend()) {
     if (HasSHA2 && HasAES)
       Features.push_back("+crypto");
@@ -823,6 +866,11 @@ llvm::ARM::FPUKind arm::getARMTargetFeatures(const Driver &D,
     else
       Features.push_back("-aes");
   }
+  // If any of these features are enabled, NEON should also be enabled.
+  if (HasAES || HasSHA2 || HasBF16 || HasDotprod || HasI8MM)
+    Features.push_back("+neon");
+
+  
 
   if (HasSHA2 || HasAES) {
     StringRef ArchSuffix = arm::getLLVMArchSuffixForARM(

clang/test/Driver/arm-features.c

@@ -74,7 +74,7 @@
 // Check +crypto for M and R profiles:
 //
 // RUN: %clang -target arm-arm-none-eabi -march=armv8-r+crypto   -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-CRYPTO-R %s
-// CHECK-CRYPTO-R: "-cc1"{{.*}} "-target-cpu" "generic"{{.*}} "-target-feature" "+sha2" "-target-feature" "+aes"
+// CHECK-CRYPTO-R: "-cc1"{{.*}} "-target-cpu" "generic"{{.*}} "-target-feature" "+sha2" "-target-feature" "+aes" "-target-feature" "+neon"
 // RUN: %clang -target arm-arm-none-eabi -march=armv8-m.base+crypto -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-NOCRYPTO5 %s
 // RUN: %clang -target arm-arm-none-eabi -march=armv8-m.main+crypto -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-NOCRYPTO5 %s
 // RUN: %clang -target arm-arm-none-eabi -mcpu=cortex-m23+crypto -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-NOCRYPTO5 %s

clang/test/Driver/arm-mfpu.c

@@ -407,7 +407,7 @@
 // CHECK-ARM8-ANDROID-FP-DEFAULT-DAG: "-target-feature" "+fp-armv8"
 // CHECK-ARM8-ANDROID-FP-DEFAULT-DAG: "-target-feature" "+aes"
 // CHECK-ARM8-ANDROID-FP-DEFAULT-DAG: "-target-feature" "+sha2"
-// CHECK-ARM8-ANDROID-FP-DEFAULT-NOT: "-target-feature" "+neon"
+// CHECK-ARM8-ANDROID-FP-DEFAULT-DAG: "-target-feature" "+neon"
 
 // RUN: %clang -target armv8-linux-android %s -### -c 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-ARM8-ANDROID-DEFAULT %s
@@ -416,7 +416,7 @@
 // CHECK-ARM8-ANDROID-DEFAULT-DAG: "-target-feature" "+fp-armv8"
 // CHECK-ARM8-ANDROID-DEFAULT-DAG: "-target-feature" "+aes"
 // CHECK-ARM8-ANDROID-DEFAULT-DAG: "-target-feature" "+sha2"
-// CHECK-ARM8-ANDROID-DEFAULT-NOT: "-target-feature" "+neon"
+// CHECK-ARM8-ANDROID-DEFAULT-DAG: "-target-feature" "+neon"
 
 // RUN: %clang -target armv7-linux-androideabi21 %s -mfpu=vfp3-d16 -### -c 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-ARM7-ANDROID-FP-D16 %s

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

@@ -1036,10 +1036,16 @@
 // CHECK-SIMD: #define __ARM_NEON_FP 0x6
 // CHECK-SIMD: #define __ARM_NEON__ 1
 
-// Check that on AArch32 appropriate targets, +nosimd correctly disables NEON instructions.
-// RUN:  %clang -target arm-none-eabi -march=armv8-a+nosimd -mfloat-abi=hard -x c -E -dM -o - %s | FileCheck -check-prefix=CHECK-NOSIMD %s
+// Check that on AArch32 appropriate targets, +nosimd correctly disables NEON instructions. All features that rely on NEON should also be disabled.
+// RUN:  %clang -target arm-none-eabi -march=armv9.6-a+nosimd -mfloat-abi=hard -x c -E -dM -o - %s | FileCheck -check-prefix=CHECK-NOSIMD %s
 // RUN:  %clang -target arm-none-eabi -mcpu=cortex-r52+nosimd -mfloat-abi=hard -x c -E -dM -o - %s | FileCheck -check-prefix=CHECK-NOSIMD %s
 // RUN:  %clang -target arm-none-eabi -mcpu=cortex-a57+nosimd -mfloat-abi=hard -x c -E -dM -o - %s | FileCheck -check-prefix=CHECK-NOSIMD %s
+// CHECK-NOSIMD-NOT: #define __ARM_FEATURE_BF16 1
+// CHECK-NOSIMD-NOT: #define __ARM_FEATURE_BF16_VECTOR_ARITHMETIC 1
+// CHECK-NOSIMD-NOT: #define __ARM_FEATURE_AES 1
+// CHECK-NOSIMD-NOT: #define __ARM_FEATURE_CRYPTO 1
+// CHECK-NOSIMD-NOT: #define __ARM_FEATURE_DOTPROD 1
+// CHECK-NOSIMD-NOT: #define __ARM_FEATURE_SHA2 1
 // CHECK-NOSIMD-NOT: #define __ARM_NEON 1
 // CHECK-NOSIMD-NOT: #define __ARM_NEON_FP 0x6
 // CHECK-NOSIMD-NOT: #define __ARM_NEON__ 1