[Clang] Remove preprocessor guards and global feature checks for NEON

[Lukacma]

To enable function multi-versioning (FMV), current checks which rely on cmd line options or global macros to see if target feature is present need to be removed. This patch removes those for NEON and also implements changes to NEON header file as proposed in ACLE.

[llvmbot]

@llvm/pr-subscribers-clang

Author: None (Lukacma)

Changes

To enable function multi-versioning (FMV), current checks which rely on cmd line options or global macros to see if target feature is present need to be removed. This patch removes those for NEON and also implements changes to NEON header file as proposed in ACLE.

---

Full diff: https://github.com/llvm/llvm-project/pull/95102.diff

4 Files Affected:

• (modified) clang/lib/Sema/SemaType.cpp (-23)
• (modified) clang/test/Sema/arm-vector-types-support.c (-2)
• (removed) clang/test/SemaCUDA/neon-attrs.cu (-22)
• (modified) clang/utils/TableGen/NeonEmitter.cpp (-5)

diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index 441fdcca0758f..65b87f62e294f 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -8084,29 +8084,6 @@ static void HandleNeonVectorTypeAttr(QualType &CurType, const ParsedAttr &Attr,
         AuxTI && (AuxTI->getTriple().isAArch64() || AuxTI->getTriple().isARM());
   }
 
-  // Target must have NEON (or MVE, whose vectors are similar enough
-  // not to need a separate attribute)
-  if (!(S.Context.getTargetInfo().hasFeature("neon") ||
-        S.Context.getTargetInfo().hasFeature("mve") ||
-        S.Context.getTargetInfo().hasFeature("sve") ||
-        S.Context.getTargetInfo().hasFeature("sme") ||
-        IsTargetCUDAAndHostARM) &&
-      VecKind == VectorKind::Neon) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_unsupported)
-        << Attr << "'neon', 'mve', 'sve' or 'sme'";
-    Attr.setInvalid();
-    return;
-  }
-  if (!(S.Context.getTargetInfo().hasFeature("neon") ||
-        S.Context.getTargetInfo().hasFeature("mve") ||
-        IsTargetCUDAAndHostARM) &&
-      VecKind == VectorKind::NeonPoly) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_unsupported)
-        << Attr << "'neon' or 'mve'";
-    Attr.setInvalid();
-    return;
-  }
-
   // Check the attribute arguments.
   if (Attr.getNumArgs() != 1) {
     S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments)
diff --git a/clang/test/Sema/arm-vector-types-support.c b/clang/test/Sema/arm-vector-types-support.c
index ed5f5ba175a94..1d2e1c9336fc6 100644
--- a/clang/test/Sema/arm-vector-types-support.c
+++ b/clang/test/Sema/arm-vector-types-support.c
@@ -2,6 +2,4 @@
 // RUN: %clang_cc1 %s -triple aarch64 -fsyntax-only -verify
 // RUN: %clang_cc1 %s -triple aarch64 -target-feature -fp-armv8 -target-abi aapcs-soft -fsyntax-only -verify
 
-typedef __attribute__((neon_vector_type(2))) int int32x2_t; // expected-error{{'neon_vector_type' attribute is not supported on targets missing 'neon', 'mve', 'sve' or 'sme'; specify an appropriate -march= or -mcpu=}}
-typedef __attribute__((neon_polyvector_type(16))) short poly8x16_t; // expected-error{{'neon_polyvector_type' attribute is not supported on targets missing 'neon' or 'mve'; specify an appropriate -march= or -mcpu=}}
 typedef __attribute__((arm_sve_vector_bits(256))) void nosveflag; // expected-error{{'arm_sve_vector_bits' attribute is not supported on targets missing 'sve'; specify an appropriate -march= or -mcpu=}}
diff --git a/clang/test/SemaCUDA/neon-attrs.cu b/clang/test/SemaCUDA/neon-attrs.cu
deleted file mode 100644
index 129056741ac9a..0000000000000
--- a/clang/test/SemaCUDA/neon-attrs.cu
+++ /dev/null
@@ -1,22 +0,0 @@
-// CPU-side compilation on ARM with neon enabled (no errors expected).
-// RUN: %clang_cc1 -triple arm64-linux-gnu -target-feature +neon -aux-triple nvptx64 -x cuda -fsyntax-only -verify=quiet %s
-
-// CPU-side compilation on ARM with neon disabled.
-// RUN: %clang_cc1 -triple arm64-linux-gnu -target-feature -neon -aux-triple nvptx64 -x cuda -fsyntax-only -verify %s
-
-// GPU-side compilation on ARM (no errors expected).
-// RUN: %clang_cc1 -triple nvptx64 -aux-triple arm64-linux-gnu -fcuda-is-device -x cuda -fsyntax-only -verify=quiet %s
-
-// Regular C++ compilation on ARM with neon enabled (no errors expected).
-// RUN: %clang_cc1 -triple arm64-linux-gnu -target-feature +neon -x c++ -fsyntax-only -verify=quiet %s
-
-// Regular C++ compilation on ARM with neon disabled.
-// RUN: %clang_cc1 -triple arm64-linux-gnu -target-feature -neon -x c++ -fsyntax-only -verify %s
-
-// quiet-no-diagnostics
-typedef __attribute__((neon_vector_type(4))) float float32x4_t;
-// expected-error@-1 {{'neon_vector_type' attribute is not supported on targets missing 'neon', 'mve', 'sve' or 'sme'}}
-// expect
-typedef unsigned char poly8_t;
-typedef __attribute__((neon_polyvector_type(8))) poly8_t poly8x8_t;
-// expected-error@-1 {{'neon_polyvector_type' attribute is not supported on targets missing 'neon' or 'mve'}}
diff --git a/clang/utils/TableGen/NeonEmitter.cpp b/clang/utils/TableGen/NeonEmitter.cpp
index 56f1fdf9ef574..626031d38cf00 100644
--- a/clang/utils/TableGen/NeonEmitter.cpp
+++ b/clang/utils/TableGen/NeonEmitter.cpp
@@ -2370,10 +2370,6 @@ void NeonEmitter::run(raw_ostream &OS) {
         "Please use -mfloat-abi=softfp or -mfloat-abi=hard\"\n";
   OS << "#else\n\n";
 
-  OS << "#if !defined(__ARM_NEON)\n";
-  OS << "#error \"NEON support not enabled\"\n";
-  OS << "#else\n\n";
-
   OS << "#include <stdint.h>\n\n";
 
   OS << "#include <arm_bf16.h>\n";
@@ -2450,7 +2446,6 @@ void NeonEmitter::run(raw_ostream &OS) {
   OS << "#undef __ai\n\n";
   OS << "#endif /* if !defined(__ARM_NEON) */\n";
   OS << "#endif /* ifndef __ARM_FP */\n";
-  OS << "#endif /* __ARM_NEON_H */\n";
 }
 
 /// run - Read the records in arm_fp16.td and output arm_fp16.h.  arm_fp16.h

[CarolineConcatto]

I believe we may need to leave still the test for MVE. We need to leave a comment in the ACLE stating that the MVE header is still needed.

[Lukacma]

Do we ? From my understanding this checks are Neon vector types and are unrelated to MVE. The only reason MVE is used is because MVE vectors are similar enough so we can use them as neon vectors

[momchil-velikov]

You can preserve the behaviour for MVE if you alter the diagnostics condition to be
"NEON type seen" && "no MVE" && "compiling for M-class".