[Hexagon] ELF attributes for Hexagon (#85359)

Defines a subset of attributes and emits them to a section called
.hexagon.attributes.

The current attributes recorded are the attributes needed by
llvm-objdump to automatically determine target features and eliminate
the need to manually pass features.

Author: quic-areg

clang/lib/Driver/ToolChains/Clang.cpp

@@ -8481,6 +8481,14 @@ void ClangAs::ConstructJob(Compilation &C, const JobAction &JA,
   case llvm::Triple::riscv64:
     AddRISCVTargetArgs(Args, CmdArgs);
     break;
+
+  case llvm::Triple::hexagon:
+    if (Args.hasFlag(options::OPT_mdefault_build_attributes,
+                     options::OPT_mno_default_build_attributes, true)) {
+      CmdArgs.push_back("-mllvm");
+      CmdArgs.push_back("-hexagon-add-build-attributes");
+    }
+    break;
   }
 
   // Consume all the warning flags. Usually this would be handled more

clang/test/Driver/hexagon-default-build-attributes.s

@@ -0,0 +1,21 @@
+/// Enabled by default for assembly
+// RUN: %clang --target=hexagon-unknown-elf -### %s 2>&1 \
+// RUN:    | FileCheck %s -check-prefix CHECK-ENABLED
+
+/// Can be forced on or off for assembly.
+// RUN: %clang --target=hexagon-unknown-elf -### %s 2>&1 -mno-default-build-attributes \
+// RUN:    | FileCheck %s -check-prefix CHECK-DISABLED
+// RUN: %clang --target=hexagon-unknown-elf -### %s 2>&1 -mdefault-build-attributes \
+// RUN:    | FileCheck %s -check-prefix CHECK-ENABLED
+
+/// Option ignored C/C++ (since we always emit hardware and ABI build attributes
+/// during codegen).
+// RUN: %clang --target=hexagon-unknown-elf -### -x c %s -mdefault-build-attributes 2>&1 \
+// RUN:    | FileCheck %s -check-prefix CHECK-DISABLED-C
+// RUN: %clang --target=hexagon-unknown-elf -### -x c++ %s -mdefault-build-attributes 2>&1 \
+// RUN:    | FileCheck %s -check-prefix CHECK-DISABLED-C
+
+// CHECK-DISABLED-NOT: "-hexagon-add-build-attributes"
+// CHECK-DISABLED-C-NOT: "-hexagon-add-build-attributes"
+// CHECK-ENABLED: "-hexagon-add-build-attributes"
+// CHECK-DISABLED-C: argument unused during compilation: '-mdefault-build-attributes'

llvm/include/llvm/BinaryFormat/ELF.h

@@ -1141,6 +1141,8 @@ enum : unsigned {
 
   SHT_CSKY_ATTRIBUTES = 0x70000001U,
 
+  SHT_HEXAGON_ATTRIBUTES = 0x70000003U,
+
   SHT_HIPROC = 0x7fffffff, // Highest processor arch-specific type.
   SHT_LOUSER = 0x80000000, // Lowest type reserved for applications.
   SHT_HIUSER = 0xffffffff  // Highest type reserved for applications.

llvm/include/llvm/Object/ELFObjectFile.h

@@ -60,6 +60,7 @@ class ELFObjectFileBase : public ObjectFile {
 
   SubtargetFeatures getMIPSFeatures() const;
   SubtargetFeatures getARMFeatures() const;
+  SubtargetFeatures getHexagonFeatures() const;
   Expected<SubtargetFeatures> getRISCVFeatures() const;
   SubtargetFeatures getLoongArchFeatures() const;
 
@@ -397,6 +398,9 @@ template <class ELFT> class ELFObjectFile : public ELFObjectFileBase {
     case ELF::EM_RISCV:
       Type = ELF::SHT_RISCV_ATTRIBUTES;
       break;
+    case ELF::EM_HEXAGON:
+      Type = ELF::SHT_HEXAGON_ATTRIBUTES;
+      break;
     default:
       return Error::success();
     }

llvm/include/llvm/Support/HexagonAttributeParser.h

@@ -0,0 +1,37 @@
+//===-- HexagonAttributeParser.h - Hexagon Attribute Parser -----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_HEXAGONATTRIBUTEPARSER_H
+#define LLVM_SUPPORT_HEXAGONATTRIBUTEPARSER_H
+
+#include "llvm/Support/ELFAttributeParser.h"
+#include "llvm/Support/HexagonAttributes.h"
+
+namespace llvm {
+class HexagonAttributeParser : public ELFAttributeParser {
+  struct DisplayHandler {
+    HexagonAttrs::AttrType Attribute;
+    Error (HexagonAttributeParser::*Routine)(unsigned);
+  };
+
+  static const DisplayHandler DisplayRoutines[];
+
+  Error handler(uint64_t Tag, bool &Handled) override;
+
+public:
+  HexagonAttributeParser(ScopedPrinter *SP)
+      : ELFAttributeParser(SP, HexagonAttrs::getHexagonAttributeTags(),
+                           "hexagon") {}
+  HexagonAttributeParser()
+      : ELFAttributeParser(HexagonAttrs::getHexagonAttributeTags(), "hexagon") {
+  }
+};
+
+} // namespace llvm
+
+#endif

llvm/include/llvm/Support/HexagonAttributes.h

@@ -0,0 +1,32 @@
+//===-- HexagonAttributes.h - Qualcomm Hexagon Attributes -----------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_HEXAGONATTRIBUTES_H
+#define LLVM_SUPPORT_HEXAGONATTRIBUTES_H
+
+#include "llvm/Support/ELFAttributes.h"
+
+namespace llvm {
+namespace HexagonAttrs {
+
+const TagNameMap &getHexagonAttributeTags();
+
+enum AttrType : unsigned {
+  ARCH = 4,
+  HVXARCH = 5,
+  HVXIEEEFP = 6,
+  HVXQFLOAT = 7,
+  ZREG = 8,
+  AUDIO = 9,
+  CABAC = 10
+};
+
+} // namespace HexagonAttrs
+} // namespace llvm
+
+#endif

llvm/lib/Object/ELF.cpp

@@ -251,7 +251,10 @@ StringRef llvm::object::getELFSectionTypeName(uint32_t Machine, unsigned Type) {
     }
     break;
   case ELF::EM_HEXAGON:
-    switch (Type) { STRINGIFY_ENUM_CASE(ELF, SHT_HEX_ORDERED); }
+    switch (Type) {
+      STRINGIFY_ENUM_CASE(ELF, SHT_HEX_ORDERED);
+      STRINGIFY_ENUM_CASE(ELF, SHT_HEXAGON_ATTRIBUTES);
+    }
     break;
   case ELF::EM_X86_64:
     switch (Type) { STRINGIFY_ENUM_CASE(ELF, SHT_X86_64_UNWIND); }

llvm/lib/Object/ELFObjectFile.cpp

@@ -20,6 +20,7 @@
 #include "llvm/Support/ARMAttributeParser.h"
 #include "llvm/Support/ARMBuildAttributes.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/HexagonAttributeParser.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/RISCVAttributeParser.h"
 #include "llvm/Support/RISCVAttributes.h"
@@ -287,6 +288,81 @@ SubtargetFeatures ELFObjectFileBase::getARMFeatures() const {
   return Features;
 }
 
+static std::optional<std::string> hexagonAttrToFeatureString(unsigned Attr) {
+  switch (Attr) {
+  case 5:
+    return "v5";
+  case 55:
+    return "v55";
+  case 60:
+    return "v60";
+  case 62:
+    return "v62";
+  case 65:
+    return "v65";
+  case 67:
+    return "v67";
+  case 68:
+    return "v68";
+  case 69:
+    return "v69";
+  case 71:
+    return "v71";
+  case 73:
+    return "v73";
+  default:
+    return {};
+  }
+}
+
+SubtargetFeatures ELFObjectFileBase::getHexagonFeatures() const {
+  SubtargetFeatures Features;
+  HexagonAttributeParser Parser;
+  if (Error E = getBuildAttributes(Parser)) {
+    // Return no attributes if none can be read.
+    // This behavior is important for backwards compatibility.
+    consumeError(std::move(E));
+    return Features;
+  }
+  std::optional<unsigned> Attr;
+
+  if ((Attr = Parser.getAttributeValue(HexagonAttrs::ARCH))) {
+    if (std::optional<std::string> FeatureString =
+            hexagonAttrToFeatureString(*Attr))
+      Features.AddFeature(*FeatureString);
+  }
+
+  if ((Attr = Parser.getAttributeValue(HexagonAttrs::HVXARCH))) {
+    std::optional<std::string> FeatureString =
+        hexagonAttrToFeatureString(*Attr);
+    // There is no corresponding hvx arch for v5 and v55.
+    if (FeatureString && *Attr >= 60)
+      Features.AddFeature("hvx" + *FeatureString);
+  }
+
+  if ((Attr = Parser.getAttributeValue(HexagonAttrs::HVXIEEEFP)))
+    if (*Attr)
+      Features.AddFeature("hvx-ieee-fp");
+
+  if ((Attr = Parser.getAttributeValue(HexagonAttrs::HVXQFLOAT)))
+    if (*Attr)
+      Features.AddFeature("hvx-qfloat");
+
+  if ((Attr = Parser.getAttributeValue(HexagonAttrs::ZREG)))
+    if (*Attr)
+      Features.AddFeature("zreg");
+
+  if ((Attr = Parser.getAttributeValue(HexagonAttrs::AUDIO)))
+    if (*Attr)
+      Features.AddFeature("audio");
+
+  if ((Attr = Parser.getAttributeValue(HexagonAttrs::CABAC)))
+    if (*Attr)
+      Features.AddFeature("cabac");
+
+  return Features;
+}
+
 Expected<SubtargetFeatures> ELFObjectFileBase::getRISCVFeatures() const {
   SubtargetFeatures Features;
   unsigned PlatformFlags = getPlatformFlags();
@@ -349,6 +425,8 @@ Expected<SubtargetFeatures> ELFObjectFileBase::getFeatures() const {
     return getRISCVFeatures();
   case ELF::EM_LOONGARCH:
     return getLoongArchFeatures();
+  case ELF::EM_HEXAGON:
+    return getHexagonFeatures();
   default:
     return SubtargetFeatures();
   }

llvm/lib/ObjectYAML/ELFYAML.cpp

@@ -716,6 +716,7 @@ void ScalarEnumerationTraits<ELFYAML::ELF_SHT>::enumeration(
     break;
   case ELF::EM_HEXAGON:
     ECase(SHT_HEX_ORDERED);
+    ECase(SHT_HEXAGON_ATTRIBUTES);
     break;
   case ELF::EM_X86_64:
     ECase(SHT_X86_64_UNWIND);

llvm/lib/Support/CMakeLists.txt

@@ -188,6 +188,8 @@ add_llvm_component_library(LLVMSupport
   GlobPattern.cpp
   GraphWriter.cpp
   Hashing.cpp
+  HexagonAttributeParser.cpp
+  HexagonAttributes.cpp
   InitLLVM.cpp
   InstructionCost.cpp
   IntEqClasses.cpp

llvm/lib/Support/HexagonAttributeParser.cpp

@@ -0,0 +1,55 @@
+//===-- HexagonAttributeParser.cpp - Hexagon Attribute Parser -------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/HexagonAttributeParser.h"
+
+using namespace llvm;
+
+const HexagonAttributeParser::DisplayHandler
+    HexagonAttributeParser::DisplayRoutines[] = {
+        {
+            HexagonAttrs::ARCH,
+            &ELFAttributeParser::integerAttribute,
+        },
+        {
+            HexagonAttrs::HVXARCH,
+            &ELFAttributeParser::integerAttribute,
+        },
+        {
+            HexagonAttrs::HVXIEEEFP,
+            &ELFAttributeParser::integerAttribute,
+        },
+        {
+            HexagonAttrs::HVXQFLOAT,
+            &ELFAttributeParser::integerAttribute,
+        },
+        {
+            HexagonAttrs::ZREG,
+            &ELFAttributeParser::integerAttribute,
+        },
+        {
+            HexagonAttrs::AUDIO,
+            &ELFAttributeParser::integerAttribute,
+        },
+        {
+            HexagonAttrs::CABAC,
+            &ELFAttributeParser::integerAttribute,
+        }};
+
+Error HexagonAttributeParser::handler(uint64_t Tag, bool &Handled) {
+  Handled = false;
+  for (const auto &R : DisplayRoutines) {
+    if (uint64_t(R.Attribute) == Tag) {
+      if (Error E = (this->*R.Routine)(Tag))
+        return E;
+      Handled = true;
+      break;
+    }
+  }
+  return Error::success();
+}

llvm/lib/Support/HexagonAttributes.cpp

@@ -0,0 +1,27 @@
+//===-- HexagonAttributes.cpp - Qualcomm Hexagon Attributes ---------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/HexagonAttributes.h"
+
+using namespace llvm;
+using namespace llvm::HexagonAttrs;
+
+static constexpr TagNameItem TagData[] = {
+    {ARCH, "Tag_arch"},
+    {HVXARCH, "Tag_hvx_arch"},
+    {HVXIEEEFP, "Tag_hvx_ieeefp"},
+    {HVXQFLOAT, "Tag_hvx_qfloat"},
+    {ZREG, "Tag_zreg"},
+    {AUDIO, "Tag_audio"},
+    {CABAC, "Tag_cabac"},
+};
+
+constexpr TagNameMap HexagonAttributeTags{TagData};
+const TagNameMap &llvm::HexagonAttrs::getHexagonAttributeTags() {
+  return HexagonAttributeTags;
+}