[AArch64][Clang] Adjust default features for v8.9-A/v9.4-A in clang driver

[pratlucas]

Summary

Update the clang driver to include the following features as default for
the v8.9-A/v9.4-A architecture versions:

• FEAT_SPECRES2
• FEAT_CSSC
• FEAT_RASv2

Patch by Sam Elliott.

[dmgreen]

Do you know why this code is in the Driver? I would have expected mandatory features to be added to the AARCH64_ARCH in AArch64TargetParser.td. I don't think they are then needed in the driver.

I can put up a patch to show what I mean, as I think the same applies to i8mm/bf16 and hbc/mops.

[dmgreen]

I've put up D141518 to move the existing features. Let me know what you think

[tmatheson]

I agree the approach in D141518 makes more sense

[pratlucas]

Updated to use the same approach as D141518.

[tmatheson]

clang/test/Driver/aarch64-cssc.c

20

Missing -###?

[pratlucas]

clang/test/Driver/aarch64-cssc.c

20

That's a consequence of the approach from D141518. The target features now go into IR attributes instead.

clang/lib/Driver/ToolChains/Arch/AArch64.cpp

Features.insert(std::next(Features.begin() + ArchFeatPos),
                     {"+i8mm", "+bf16"});
 
   // For Armv8.8-a/Armv9.3-a or later, FEAT_HBC and FEAT_MOPS are enabled by
   // default.
   if (V8Version >= 8 || V9Version >= 3)
     Features.insert(std::next(Features.begin() + ArchFeatPos),
                     {"+hbc", "+mops"});
 
+  // Default features for Armv8.9-a/Armv9.4-a or later.
+  if (V8Version >= 9 || V9Version >= 4)
+    Features.insert(std::next(Features.begin() + ArchFeatPos),
+                    {"+specres2", "+cssc", "+rasv2"});
+
   if (Arg *A = Args.getLastArg(options::OPT_mno_unaligned_access,
                                options::OPT_munaligned_access)) {
     if (A->getOption().matches(options::OPT_mno_unaligned_access))
       Features.push_back("+strict-align");
   } else if (Triple.isOSOpenBSD())
     Features.push_back("+strict-align");
 
   if (Args.hasArg(options::OPT_ffixed_x1))

clang/test/Driver/aarch64-cssc.c

 // Test that target feature cssc is implemented and available correctly
+// FEAT_CSSC is a required part of v8.9a/v9.4a and optional from v8.7a/v9.3a onwards.
 // RUN: %clang -### -target aarch64-none-none-eabi                         %s 2>&1 | FileCheck %s --check-prefix=ABSENT_CSSC
-// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.8-a+cssc   %s 2>&1 | FileCheck %s
-// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.9-a        %s 2>&1 | FileCheck %s --check-prefix=ABSENT_CSSC
-// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.8-a+cssc   %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.7-a+cssc   %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.9-a        %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.9-a+cssc   %s 2>&1 | FileCheck %s
 // RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.9-a+nocssc %s 2>&1 | FileCheck %s --check-prefix=NO_CSSC
-// RUN: %clang -### -target aarch64-none-none-eabi -march=armv9.3-a+cssc   %s 2>&1 | FileCheck %s
-// RUN: %clang -### -target aarch64-none-none-eabi -march=armv9.4-a        %s 2>&1 | FileCheck %s --check-prefix=ABSENT_CSSC
-// RUN: %clang -### -target aarch64-none-none-eabi -march=armv9.3-a+cssc   %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv9.2-a+cssc   %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv9.4-a        %s 2>&1 | FileCheck %s
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv9.4-a+cssc   %s 2>&1 | FileCheck %s
 // RUN: %clang -### -target aarch64-none-none-eabi -march=armv9.4-a+nocssc %s 2>&1 | FileCheck %s --check-prefix=NO_CSSC
 
 // CHECK: "-target-feature" "+cssc"
 // NO_CSSC: "-target-feature" "-cssc"
 // ABSENT_CSSC-NOT: "-target-feature" "+cssc"
 // ABSENT_CSSC-NOT: "-target-feature" "-cssc"