[AArch64] Define __ARM_FEATURE_RCPC

[mingmingl]

Summary

This patch implements the definition of __ARM_FEATURE_RCPC when clang commands specifies +rcpc.

[mingmingl]

update commit message with differential revision link.

[tyb0807]

The patch looks correct to me, but looking at https://github.com/ARM-software/acle/blob/main/main/acle.md where all the ACLE macros are defined, I'm not sure that __ARM_FEATURE_RCPC is there currently. Maybe you also want to submit a patch there, or at least explain the context of this change please?

[mingmingl]

In D127798#3585025, @tyb0807 wrote:

The patch looks correct to me, but looking at https://github.com/ARM-software/acle/blob/main/main/acle.md where all the ACLE macros are defined, I'm not sure that __ARM_FEATURE_RCPC is there currently. Maybe you also want to submit a patch there, or at least explain the context of this change please?

thanks for taking a look!

Before this patch, there is a piece of inline assembly like [1] that uses LDAPR and guarded by #if defined(__aarch64__). Since not all aarch64 platforms support LDAPR, we want to further guard the usage of LDAPR by MACRO __ARM_FEATURE_RCPC. May I know if there are alternatives for this use case, if introducing __ARM_FEATURE_RCPC sounds ad-hoc?

I'm glad to send a patch to add __ARM_FEATURE_RCPC to https://github.com/ARM-software/acle/blob/main/main/acle.md if it's conventional to do so. Just let me know your suggestions!

[1]

add x6, x1, x4
ldapr x5, [x6]

[lenary]

Yes. Please submit a PR or Issue to the ACLE, explaining the use-case (the explanation here is good enough, I think).

Once the ACLE changes are merged, then you can proceed with a patch for clang.

[mingmingl]

In D127798#3588283, @lenary wrote:

Yes. Please submit a PR or Issue to the ACLE, explaining the use-case (the explanation here is good enough, I think).

Once the ACLE changes are merged, then you can proceed with a patch for clang.

This makes sense to me. I created https://github.com/ARM-software/acle/pull/199, yet not able to add reviewer (which is WAI since I don't have write permission).

[MaskRay]

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

22

The list is alphabetical. RCPC should be moved below.

565

--target=aarch64

[mingmingl]

In clang/test/Preprocessor/aarch64-target-features.c, move __ARM_FEATURE_RCPC to keep the alphabetical list, and use -target=aarch64.. (the join style) rather than legacy while-space separated style (key value).

[mingmingl]

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

22

good catch. done.

565

done. thanks for pointing this out!

[mingmingl]

change from -target=aarch64-none-linux-gnu to --target=aarch64-none-linux-gnu to resolve a compile error.

Verified no other compilation error by ninja check-all

[mingmingl]

Use --target=aarch64 rather than --target=aarch64-unknown-linux-gnu, given the former means all ELF based operating systems can expect the feature. (thanks maskray@ for pointing it out!)

[mingmingl]

It has been a while since this patch was updated, rebase for review now that the Github PR was accepted.

[mingmingl]

Hi folks,
The ARM ACLE PR (https://github.com/ARM-software/acle/pull/199) was accepted. Would you take another look of this patch at your convenience? Thanks!

[mingmingl]

Thanks! Going to submit.

clang/lib/Basic/Targets/AArch64.h

class LLVM_LIBRARY_VISIBILITY AArch64TargetInfo : public TargetInfo {
   bool HasSVE2SHA3;
   bool HasSVE2SM4;
   bool HasSVE2BitPerm;
   bool HasMatmulFP64;
   bool HasMatmulFP32;
   bool HasLSE;
   bool HasFlagM;
   bool HasMOPS;
+  bool HasRCPC;
 
   llvm::AArch64::ArchKind ArchKind;
 
   static const Builtin::Info BuiltinInfo[];
 
   std::string ABI;
   StringRef getArchProfile() const;
 

clang/lib/Basic/Targets/AArch64.cpp

if (HasSVE2 && HasSVE2SHA3)
     Builder.defineMacro("__ARM_FEATURE_SVE2_SHA3", "1");
 
   if (HasSVE2 && HasSVE2SM4)
     Builder.defineMacro("__ARM_FEATURE_SVE2_SM4", "1");
 
   if (HasCRC)
     Builder.defineMacro("__ARM_FEATURE_CRC32", "1");
 
+  if (HasRCPC)
+    Builder.defineMacro("__ARM_FEATURE_RCPC", "1");
+
   // The __ARM_FEATURE_CRYPTO is deprecated in favor of finer grained feature
   // macros for AES, SHA2, SHA3 and SM4
   if (HasAES && HasSHA2)
     Builder.defineMacro("__ARM_FEATURE_CRYPTO", "1");
 
   if (HasAES)
     Builder.defineMacro("__ARM_FEATURE_AES", "1");
 
bool AArch64TargetInfo::handleTargetFeatures(std::vector<std::string> &Features,
   HasSVE2AES = false;
   HasSVE2SHA3 = false;
   HasSVE2SM4 = false;
   HasSVE2BitPerm = false;
   HasMatmulFP64 = false;
   HasMatmulFP32 = false;
   HasLSE = false;
   HasMOPS = false;
+  HasRCPC = false;
 
   ArchKind = llvm::AArch64::ArchKind::INVALID;
 
   for (const auto &Feature : Features) {
     if (Feature == "+neon")
       FPU |= NeonMode;
     if (Feature == "+sve") {
       FPU |= SveMode;
if (Feature == "+f32mm") {
       HasMatmulFP32 = true;
     }
     if (Feature == "+f64mm") {
       FPU |= SveMode;
       HasMatmulFP64 = true;
     }
     if (Feature == "+crc")
       HasCRC = true;
+    if (Feature == "+rcpc")
+      HasRCPC = true;
     if (Feature == "+aes")
       HasAES = true;
     if (Feature == "+sha2")
       HasSHA2 = true;
     if (Feature == "+sha3") {
       HasSHA2 = true;
       HasSHA3 = true;
     }

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

 // CHECK-NOT: __ARM_FEATURE_DSP
 // CHECK-NOT: __ARM_FEATURE_SAT
 // CHECK-NOT: __ARM_FEATURE_SIMD32
 // CHECK: __ARM_ARCH_PROFILE 'A'
 // CHECK-NOT: __ARM_FEATURE_AES
 // CHECK-NOT: __ARM_FEATURE_BIG_ENDIAN
 // CHECK: __ARM_FEATURE_CLZ 1
 // CHECK-NOT: __ARM_FEATURE_CRC32 1
 // CHECK-NOT: __ARM_FEATURE_CRYPTO 1
 // CHECK: __ARM_FEATURE_DIRECTED_ROUNDING 1
 // CHECK: __ARM_FEATURE_DIV 1
 // CHECK: __ARM_FEATURE_FMA 1
 // CHECK: __ARM_FEATURE_IDIV 1
 // CHECK: __ARM_FEATURE_LDREX 0xF
 // CHECK: __ARM_FEATURE_NUMERIC_MAXMIN 1
+// CHECK-NOT: __ARM_FEATURE_RCPC 1
 // CHECK-NOT: __ARM_FEATURE_SHA2 1
 // CHECK-NOT: __ARM_FEATURE_SHA3 1
 // CHECK-NOT: __ARM_FEATURE_SHA512 1
 // CHECK-NOT: __ARM_FEATURE_SM3 1
 // CHECK-NOT: __ARM_FEATURE_SM4 1
 // CHECK: __ARM_FEATURE_UNALIGNED 1
 // CHECK: __ARM_FP 0xE
 // CHECK: __ARM_FP16_ARGS 1

 // CHECK-V83-OR-LATER: __ARM_FEATURE_COMPLEX 1
 // CHECK-V81-OR-LATER: __ARM_FEATURE_CRC32 1
 // CHECK-V85-OR-LATER: __ARM_FEATURE_FRINT 1
 // CHECK-V83-OR-LATER: __ARM_FEATURE_JCVT 1
 // CHECK-V81-OR-LATER: __ARM_FEATURE_QRDMX 1
 // CHECK-BEFORE-V83-NOT: __ARM_FEATURE_COMPLEX 1
 // CHECK-BEFORE-V83-NOT: __ARM_FEATURE_JCVT 1
 // CHECK-BEFORE-V85-NOT: __ARM_FEATURE_FRINT 1
+
+// RUN: %clang --target=aarch64 -march=armv8.2-a+rcpc -x c -E -dM %s -o - | FileCheck --check-prefix=CHECK-RCPC %s
+// CHECK-RCPC: __ARM_FEATURE_RCPC 1