[clang] [Clang] Remove AArch64TargetInfo::setArchFeatures (PR #146107)

[Sander de Smalen via cfe-commits]

https://github.com/sdesmalen-arm updated https://github.com/llvm/llvm-project/pull/146107

>From c44ab034e0f1a54df2a3f5c09ddabff531dea982 Mon Sep 17 00:00:00 2001
From: Sander de Smalen <sander.desmalen at arm.com>
Date: Fri, 27 Jun 2025 16:12:04 +0000
Subject: [PATCH] [Clang] Remove AArch64TargetInfo::setArchFeatures

When compiling with `-march=armv9-a+nosve` we found that Clang
still defines the `__ARM_FEATURE_SVE2` macro, which is explicitly
set in `setArchFeatures` when compiling for armv9-a.

After some experimenting, I found out that the list of features
passed into `AArch64TargetInfo::handleTargetFeatures` has already
been expanded and takes into account `+no[feature]` and has
already expanded features like `armv9-a`.

>From that I conclude that `setArchFeatures` is no longer required.
---
 clang/lib/Basic/Targets/AArch64.cpp           | 74 -------------------
 clang/lib/Basic/Targets/AArch64.h             |  2 -
 clang/test/Preprocessor/arm-target-features.c |  5 ++
 3 files changed, 5 insertions(+), 76 deletions(-)

diff --git a/clang/lib/Basic/Targets/AArch64.cpp b/clang/lib/Basic/Targets/AArch64.cpp
index 124b340b62d9f..e57feafe3ae24 100644
--- a/clang/lib/Basic/Targets/AArch64.cpp
+++ b/clang/lib/Basic/Targets/AArch64.cpp
@@ -125,79 +125,6 @@ static constexpr auto BuiltinAArch64Infos =
 #include "clang/Basic/BuiltinsAArch64.def"
     });
 
-void AArch64TargetInfo::setArchFeatures() {
-  if (*ArchInfo == llvm::AArch64::ARMV8R) {
-    HasDotProd = true;
-    HasDIT = true;
-    HasFlagM = true;
-    HasRCPC = true;
-    FPU |= NeonMode;
-    HasCCPP = true;
-    HasCRC = true;
-    HasLSE = true;
-    HasRDM = true;
-  } else if (ArchInfo->Version.getMajor() == 8) {
-    if (ArchInfo->Version.getMinor() >= 7u) {
-      HasWFxT = true;
-    }
-    if (ArchInfo->Version.getMinor() >= 6u) {
-      HasBFloat16 = true;
-      HasMatMul = true;
-    }
-    if (ArchInfo->Version.getMinor() >= 5u) {
-      HasAlternativeNZCV = true;
-      HasFRInt3264 = true;
-      HasSSBS = true;
-      HasSB = true;
-      HasPredRes = true;
-      HasBTI = true;
-    }
-    if (ArchInfo->Version.getMinor() >= 4u) {
-      HasDotProd = true;
-      HasDIT = true;
-      HasFlagM = true;
-    }
-    if (ArchInfo->Version.getMinor() >= 3u) {
-      HasRCPC = true;
-      FPU |= NeonMode;
-    }
-    if (ArchInfo->Version.getMinor() >= 2u) {
-      HasCCPP = true;
-    }
-    if (ArchInfo->Version.getMinor() >= 1u) {
-      HasCRC = true;
-      HasLSE = true;
-      HasRDM = true;
-    }
-  } else if (ArchInfo->Version.getMajor() == 9) {
-    if (ArchInfo->Version.getMinor() >= 2u) {
-      HasWFxT = true;
-    }
-    if (ArchInfo->Version.getMinor() >= 1u) {
-      HasBFloat16 = true;
-      HasMatMul = true;
-    }
-    FPU |= SveMode;
-    HasSVE2 = true;
-    HasFullFP16 = true;
-    HasAlternativeNZCV = true;
-    HasFRInt3264 = true;
-    HasSSBS = true;
-    HasSB = true;
-    HasPredRes = true;
-    HasBTI = true;
-    HasDotProd = true;
-    HasDIT = true;
-    HasFlagM = true;
-    HasRCPC = true;
-    FPU |= NeonMode;
-    HasCCPP = true;
-    HasCRC = true;
-    HasLSE = true;
-    HasRDM = true;
-  }
-}
-
 AArch64TargetInfo::AArch64TargetInfo(const llvm::Triple &Triple,
                                      const TargetOptions &Opts)
     : TargetInfo(Triple), ABI("aapcs") {
@@ -1266,7 +1193,6 @@ bool AArch64TargetInfo::handleTargetFeatures(std::vector<std::string> &Features,
   }
 
   setDataLayout();
-  setArchFeatures();
 
   if (HasNoFP) {
     FPU &= ~FPUMode;
diff --git a/clang/lib/Basic/Targets/AArch64.h b/clang/lib/Basic/Targets/AArch64.h
index 1951e0679d2ec..56adfa97efb1a 100644
--- a/clang/lib/Basic/Targets/AArch64.h
+++ b/clang/lib/Basic/Targets/AArch64.h
@@ -158,8 +158,6 @@ class LLVM_LIBRARY_VISIBILITY AArch64TargetInfo : public TargetInfo {
     return false;
   }
 
-  void setArchFeatures();
-
   void getTargetDefinesARMV81A(const LangOptions &Opts,
                                MacroBuilder &Builder) const;
   void getTargetDefinesARMV82A(const LangOptions &Opts,
diff --git a/clang/test/Preprocessor/arm-target-features.c b/clang/test/Preprocessor/arm-target-features.c
index 0f9063a27371e..fc37bebcb8330 100644
--- a/clang/test/Preprocessor/arm-target-features.c
+++ b/clang/test/Preprocessor/arm-target-features.c
@@ -1049,3 +1049,8 @@
 // CHECK-NOSIMD-NOT: #define __ARM_NEON 1
 // CHECK-NOSIMD-NOT: #define __ARM_NEON_FP 0x6
 // CHECK-NOSIMD-NOT: #define __ARM_NEON__ 1
+
+// Check that disabling SVE, as set by armv9-a, does not define __ARM_FEATURE_SVE* macros.
+// RUN:  %clang -target aarch64 -march=armv9-a+nosve -x c -E -dM -o - %s | FileCheck -check-prefix=CHECK-NOSVE %s
+// CHECK-NOSVE-NOT: #define __ARM_FEATURE_SVE 1
+// CHECK-NOSVE-NOT: #define __ARM_FEATURE_SVE2 1