[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.

2 files changed, 82 insertions, 1 deletions

diff --git a/llvm/lib/Object/ELF.cpp b/llvm/lib/Object/ELF.cpp
index 137f606..55dd0c8 100644
--- a/llvm/lib/Object/ELF.cpp
+++ b/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); }
diff --git a/llvm/lib/Object/ELFObjectFile.cpp b/llvm/lib/Object/ELFObjectFile.cpp
index 33be481..efec612 100644
--- a/llvm/lib/Object/ELFObjectFile.cpp
+++ b/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();
   }