[AArch64] Decouple feature dependency expansion. (llvm#94279)

The dependency expansion step which was introduced by FMV has been
erroneously used for non-FMV features, for example when parsing the
target attribute. The PR llvm#93695 has rectified most of the tests which
were relying on dependency expansion of target features specified on the
-cc1 command line. In this patch I am decoupling the dependency
expansion of features specified on the target attribute from FMV.

To do that first I am expanding FMV dependencies before passing the list
of target features to initFeatureMap(). Similarly when parsing the
target attribute I am reconstructing an ExtensionSet from the list of
target features which was created during the command line option
parsing. The attribute parsing may toggle bits of that ExtensionSet and
at the end it is converted to a list of target features. Those are
passed to initFeatureMap(), which no longer requires an override.

A side effect of this refactoring is that features specified on the
target_version attribute now supersede the command line options, which
is what should be happening in the first place.

Author: labrinea

clang/include/clang/AST/ASTContext.h

@@ -3203,9 +3203,6 @@ class ASTContext : public RefCountedBase<ASTContext> {
   /// valid feature names.
   ParsedTargetAttr filterFunctionTargetAttrs(const TargetAttr *TD) const;
 
-  std::vector<std::string>
-  filterFunctionTargetVersionAttrs(const TargetVersionAttr *TV) const;
-
   void getFunctionFeatureMap(llvm::StringMap<bool> &FeatureMap,
                              const FunctionDecl *) const;
   void getFunctionFeatureMap(llvm::StringMap<bool> &FeatureMap,

clang/lib/AST/ASTContext.cpp

@@ -87,6 +87,7 @@
 #include "llvm/Support/MD5.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/TargetParser/AArch64TargetParser.h"
 #include "llvm/TargetParser/Triple.h"
 #include <algorithm>
 #include <cassert>
@@ -13663,17 +13664,20 @@ QualType ASTContext::getCorrespondingSignedFixedPointType(QualType Ty) const {
   }
 }
 
-std::vector<std::string> ASTContext::filterFunctionTargetVersionAttrs(
-    const TargetVersionAttr *TV) const {
-  assert(TV != nullptr);
-  llvm::SmallVector<StringRef, 8> Feats;
-  std::vector<std::string> ResFeats;
-  TV->getFeatures(Feats);
-  for (auto &Feature : Feats)
-    if (Target->validateCpuSupports(Feature.str()))
-      // Use '?' to mark features that came from TargetVersion.
-      ResFeats.push_back("?" + Feature.str());
-  return ResFeats;
+// Given a list of FMV features, return a concatenated list of the
+// corresponding backend features (which may contain duplicates).
+static std::vector<std::string> getFMVBackendFeaturesFor(
+    const llvm::SmallVectorImpl<StringRef> &FMVFeatStrings) {
+  std::vector<std::string> BackendFeats;
+  for (StringRef F : FMVFeatStrings) {
+    if (auto FMVExt = llvm::AArch64::parseArchExtension(F)) {
+      SmallVector<StringRef, 8> Feats;
+      FMVExt->DependentFeatures.split(Feats, ',', -1, false);
+      for (StringRef F : Feats)
+        BackendFeats.push_back(F.str());
+    }
+  }
+  return BackendFeats;
 }
 
 ParsedTargetAttr
@@ -13708,10 +13712,12 @@ void ASTContext::getFunctionFeatureMap(llvm::StringMap<bool> &FeatureMap,
 
     // Make a copy of the features as passed on the command line into the
     // beginning of the additional features from the function to override.
-    ParsedAttr.Features.insert(
-        ParsedAttr.Features.begin(),
-        Target->getTargetOpts().FeaturesAsWritten.begin(),
-        Target->getTargetOpts().FeaturesAsWritten.end());
+    // AArch64 handles command line option features in parseTargetAttr().
+    if (!Target->getTriple().isAArch64())
+      ParsedAttr.Features.insert(
+          ParsedAttr.Features.begin(),
+          Target->getTargetOpts().FeaturesAsWritten.begin(),
+          Target->getTargetOpts().FeaturesAsWritten.end());
 
     if (ParsedAttr.CPU != "" && Target->isValidCPUName(ParsedAttr.CPU))
       TargetCPU = ParsedAttr.CPU;
@@ -13732,32 +13738,31 @@ void ASTContext::getFunctionFeatureMap(llvm::StringMap<bool> &FeatureMap,
                     Target->getTargetOpts().FeaturesAsWritten.end());
     Target->initFeatureMap(FeatureMap, getDiagnostics(), TargetCPU, Features);
   } else if (const auto *TC = FD->getAttr<TargetClonesAttr>()) {
-    std::vector<std::string> Features;
     if (Target->getTriple().isAArch64()) {
-      // TargetClones for AArch64
       llvm::SmallVector<StringRef, 8> Feats;
       TC->getFeatures(Feats, GD.getMultiVersionIndex());
-      for (StringRef Feat : Feats)
-        if (Target->validateCpuSupports(Feat.str()))
-          // Use '?' to mark features that came from AArch64 TargetClones.
-          Features.push_back("?" + Feat.str());
+      std::vector<std::string> Features = getFMVBackendFeaturesFor(Feats);
       Features.insert(Features.begin(),
                       Target->getTargetOpts().FeaturesAsWritten.begin(),
                       Target->getTargetOpts().FeaturesAsWritten.end());
+      Target->initFeatureMap(FeatureMap, getDiagnostics(), TargetCPU, Features);
     } else {
+      std::vector<std::string> Features;
       StringRef VersionStr = TC->getFeatureStr(GD.getMultiVersionIndex());
       if (VersionStr.starts_with("arch="))
         TargetCPU = VersionStr.drop_front(sizeof("arch=") - 1);
       else if (VersionStr != "default")
         Features.push_back((StringRef{"+"} + VersionStr).str());
+      Target->initFeatureMap(FeatureMap, getDiagnostics(), TargetCPU, Features);
     }
-    Target->initFeatureMap(FeatureMap, getDiagnostics(), TargetCPU, Features);
   } else if (const auto *TV = FD->getAttr<TargetVersionAttr>()) {
-    std::vector<std::string> Feats = filterFunctionTargetVersionAttrs(TV);
-    Feats.insert(Feats.begin(),
-                 Target->getTargetOpts().FeaturesAsWritten.begin(),
-                 Target->getTargetOpts().FeaturesAsWritten.end());
-    Target->initFeatureMap(FeatureMap, getDiagnostics(), TargetCPU, Feats);
+    llvm::SmallVector<StringRef, 8> Feats;
+    TV->getFeatures(Feats);
+    std::vector<std::string> Features = getFMVBackendFeaturesFor(Feats);
+    Features.insert(Features.begin(),
+                    Target->getTargetOpts().FeaturesAsWritten.begin(),
+                    Target->getTargetOpts().FeaturesAsWritten.end());
+    Target->initFeatureMap(FeatureMap, getDiagnostics(), TargetCPU, Features);
   } else {
     FeatureMap = Target->getTargetOpts().FeatureMap;
   }

clang/lib/Basic/Targets/AArch64.cpp

@@ -1050,57 +1050,18 @@ bool AArch64TargetInfo::handleTargetFeatures(std::vector<std::string> &Features,
   return true;
 }
 
-bool AArch64TargetInfo::initFeatureMap(
-    llvm::StringMap<bool> &Features, DiagnosticsEngine &Diags, StringRef CPU,
-    const std::vector<std::string> &FeaturesVec) const {
-  std::vector<std::string> UpdatedFeaturesVec;
-  // Parse the CPU and add any implied features.
-  std::optional<llvm::AArch64::CpuInfo> CpuInfo = llvm::AArch64::parseCpu(CPU);
-  if (CpuInfo) {
-    auto Exts = CpuInfo->getImpliedExtensions();
-    std::vector<StringRef> CPUFeats;
-    llvm::AArch64::getExtensionFeatures(Exts, CPUFeats);
-    for (auto F : CPUFeats) {
-      assert((F[0] == '+' || F[0] == '-') && "Expected +/- in target feature!");
-      UpdatedFeaturesVec.push_back(F.str());
-    }
-  }
-
-  // Process target and dependent features. This is done in two loops collecting
-  // them into UpdatedFeaturesVec: first to add dependent '+'features, second to
-  // add target '+/-'features that can later disable some of features added on
-  // the first loop. Function Multi Versioning features begin with '?'.
-  for (const auto &Feature : FeaturesVec)
-    if (((Feature[0] == '?' || Feature[0] == '+')) &&
-        AArch64TargetInfo::doesFeatureAffectCodeGen(Feature.substr(1))) {
-      StringRef DepFeatures =
-          AArch64TargetInfo::getFeatureDependencies(Feature.substr(1));
-      SmallVector<StringRef, 1> AttrFeatures;
-      DepFeatures.split(AttrFeatures, ",");
-      for (auto F : AttrFeatures)
-        UpdatedFeaturesVec.push_back(F.str());
-    }
-  for (const auto &Feature : FeaturesVec)
-    if (Feature[0] != '?') {
-      std::string UpdatedFeature = Feature;
-      if (Feature[0] == '+') {
-        std::optional<llvm::AArch64::ExtensionInfo> Extension =
-          llvm::AArch64::parseArchExtension(Feature.substr(1));
-        if (Extension)
-          UpdatedFeature = Extension->Feature.str();
-      }
-      UpdatedFeaturesVec.push_back(UpdatedFeature);
-    }
-
-  return TargetInfo::initFeatureMap(Features, Diags, CPU, UpdatedFeaturesVec);
-}
-
 // Parse AArch64 Target attributes, which are a comma separated list of:
 //  "arch=<arch>" - parsed to features as per -march=..
 //  "cpu=<cpu>" - parsed to features as per -mcpu=.., with CPU set to <cpu>
 //  "tune=<cpu>" - TuneCPU set to <cpu>
 //  "feature", "no-feature" - Add (or remove) feature.
 //  "+feature", "+nofeature" - Add (or remove) feature.
+//
+// A feature may correspond to an Extension (anything with a corresponding
+// AEK_), in which case an ExtensionSet is used to parse it and expand its
+// dependencies. Otherwise the feature is passed through (e.g. +v8.1a,
+// +outline-atomics, -fmv, etc). Features coming from the command line are
+// already parsed, therefore their dependencies do not need expansion.
 ParsedTargetAttr AArch64TargetInfo::parseTargetAttr(StringRef Features) const {
   ParsedTargetAttr Ret;
   if (Features == "default")
@@ -1110,23 +1071,26 @@ ParsedTargetAttr AArch64TargetInfo::parseTargetAttr(StringRef Features) const {
   bool FoundArch = false;
 
   auto SplitAndAddFeatures = [](StringRef FeatString,
-                                std::vector<std::string> &Features) {
+                                std::vector<std::string> &Features,
+                                llvm::AArch64::ExtensionSet &FeatureBits) {
     SmallVector<StringRef, 8> SplitFeatures;
     FeatString.split(SplitFeatures, StringRef("+"), -1, false);
     for (StringRef Feature : SplitFeatures) {
-      StringRef FeatureName = llvm::AArch64::getArchExtFeature(Feature);
-      if (!FeatureName.empty())
-        Features.push_back(FeatureName.str());
+      if (FeatureBits.parseModifier(Feature, /* AllowNoDashForm = */ true))
+        continue;
+      // Pass through features that are not extensions, e.g. +v8.1a,
+      // +outline-atomics, -fmv, etc.
+      if (Feature.starts_with("no"))
+        Features.push_back("-" + Feature.drop_front(2).str());
       else
-        // Pushing the original feature string to give a sema error later on
-        // when they get checked.
-        if (Feature.starts_with("no"))
-          Features.push_back("-" + Feature.drop_front(2).str());
-        else
-          Features.push_back("+" + Feature.str());
+        Features.push_back("+" + Feature.str());
     }
   };
 
+  llvm::AArch64::ExtensionSet FeatureBits;
+  // Reconstruct the bitset from the command line option features.
+  FeatureBits.reconstructFromParsedFeatures(getTargetOpts().FeaturesAsWritten);
+
   for (auto &Feature : AttrFeatures) {
     Feature = Feature.trim();
     if (Feature.starts_with("fpmath="))
@@ -1149,9 +1113,9 @@ ParsedTargetAttr AArch64TargetInfo::parseTargetAttr(StringRef Features) const {
       // Ret.Features.
       if (!AI)
         continue;
-      Ret.Features.push_back(AI->ArchFeature.str());
+      FeatureBits.addArchDefaults(*AI);
       // Add any extra features, after the +
-      SplitAndAddFeatures(Split.second, Ret.Features);
+      SplitAndAddFeatures(Split.second, Ret.Features, FeatureBits);
     } else if (Feature.starts_with("cpu=")) {
       if (!Ret.CPU.empty())
         Ret.Duplicate = "cpu=";
@@ -1161,33 +1125,30 @@ ParsedTargetAttr AArch64TargetInfo::parseTargetAttr(StringRef Features) const {
         std::pair<StringRef, StringRef> Split =
             Feature.split("=").second.trim().split("+");
         Ret.CPU = Split.first;
-        SplitAndAddFeatures(Split.second, Ret.Features);
+        if (auto CpuInfo = llvm::AArch64::parseCpu(Ret.CPU)) {
+          FeatureBits.addCPUDefaults(*CpuInfo);
+          SplitAndAddFeatures(Split.second, Ret.Features, FeatureBits);
+        }
       }
     } else if (Feature.starts_with("tune=")) {
       if (!Ret.Tune.empty())
         Ret.Duplicate = "tune=";
       else
         Ret.Tune = Feature.split("=").second.trim();
     } else if (Feature.starts_with("+")) {
-      SplitAndAddFeatures(Feature, Ret.Features);
-    } else if (Feature.starts_with("no-")) {
-      StringRef FeatureName =
-          llvm::AArch64::getArchExtFeature(Feature.split("-").second);
-      if (!FeatureName.empty())
-        Ret.Features.push_back("-" + FeatureName.drop_front(1).str());
-      else
-        Ret.Features.push_back("-" + Feature.split("-").second.str());
+      SplitAndAddFeatures(Feature, Ret.Features, FeatureBits);
     } else {
-      // Try parsing the string to the internal target feature name. If it is
-      // invalid, add the original string (which could already be an internal
-      // name). These should be checked later by isValidFeatureName.
-      StringRef FeatureName = llvm::AArch64::getArchExtFeature(Feature);
-      if (!FeatureName.empty())
-        Ret.Features.push_back(FeatureName.str());
+      if (FeatureBits.parseModifier(Feature, /* AllowNoDashForm = */ true))
+        continue;
+      // Pass through features that are not extensions, e.g. +v8.1a,
+      // +outline-atomics, -fmv, etc.
+      if (Feature.starts_with("no-"))
+        Ret.Features.push_back("-" + Feature.drop_front(3).str());
       else
         Ret.Features.push_back("+" + Feature.str());
     }
   }
+  FeatureBits.toLLVMFeatureList(Ret.Features);
   return Ret;
 }
 

clang/lib/Basic/Targets/AArch64.h

@@ -107,10 +107,6 @@ class LLVM_LIBRARY_VISIBILITY AArch64TargetInfo : public TargetInfo {
   unsigned multiVersionSortPriority(StringRef Name) const override;
   unsigned multiVersionFeatureCost() const override;
 
-  bool
-  initFeatureMap(llvm::StringMap<bool> &Features, DiagnosticsEngine &Diags,
-                 StringRef CPU,
-                 const std::vector<std::string> &FeaturesVec) const override;
   bool useFP16ConversionIntrinsics() const override {
     return false;
   }

clang/test/CodeGen/aarch64-cpu-supports-target.c

@@ -48,5 +48,5 @@ int test_versions() {
     return code();
 }
 // CHECK: attributes #0 = { noinline nounwind optnone "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
-// CHECK: attributes #1 = { noinline nounwind optnone "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-features"="+neon" }
-// CHECK: attributes #2 = { noinline nounwind optnone "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-features"="+fp-armv8,+fullfp16,+neon,+sve" }
+// CHECK: attributes #1 = { noinline nounwind optnone "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-features"="+fp-armv8,+neon" }
+// CHECK: attributes #2 = { noinline nounwind optnone "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-features"="+fp-armv8,+fullfp16,+sve" }

clang/test/CodeGen/aarch64-sme-intrinsics/aarch64-sme-attrs.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +sme \
+// RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +sme -target-feature +bf16 \
 // RUN:   -disable-O0-optnone -Werror -emit-llvm -o - %s \
 // RUN: | opt -S -passes=mem2reg \
 // RUN: | opt -S -passes=inline \