[SPARC][IAS] Add v8plus feature bit (#101367)

Implement handling for `v8plus` feature bit to allow the user to switch
between V8 and V8+ mode with 32-bit code.
Currently this only sets the appropriate ELF machine type and flags;
codegen changes will be done in future patches.

This is done as a prerequisite for `-mv8plus` flag on clang (#98713).

Author: koachan

llvm/include/llvm/BinaryFormat/ELF.h

@@ -697,6 +697,19 @@ enum {
 #include "ELFRelocs/SystemZ.def"
 };
 
+// SPARC Specific e_flags
+enum : unsigned {
+  EF_SPARC_EXT_MASK = 0xffff00,
+  EF_SPARC_32PLUS = 0x000100,
+  EF_SPARC_SUN_US1 = 0x000200,
+  EF_SPARC_HAL_R1 = 0x000400,
+  EF_SPARC_SUN_US3 = 0x000800,
+  EF_SPARCV9_MM = 0x3,
+  EF_SPARCV9_TSO = 0x0,
+  EF_SPARCV9_PSO = 0x1,
+  EF_SPARCV9_RMO = 0x2,
+};
+
 // ELF Relocation type for Sparc.
 enum {
 #include "ELFRelocs/Sparc.def"

llvm/lib/Target/Sparc/MCTargetDesc/SparcAsmBackend.cpp

@@ -132,15 +132,15 @@ namespace {
   class SparcAsmBackend : public MCAsmBackend {
   protected:
     bool Is64Bit;
-    bool HasV9;
+    bool IsV8Plus;
 
   public:
     SparcAsmBackend(const MCSubtargetInfo &STI)
         : MCAsmBackend(STI.getTargetTriple().isLittleEndian()
                            ? llvm::endianness::little
                            : llvm::endianness::big),
           Is64Bit(STI.getTargetTriple().isArch64Bit()),
-          HasV9(STI.hasFeature(Sparc::FeatureV9)) {}
+          IsV8Plus(STI.hasFeature(Sparc::FeatureV8Plus)) {}
 
     unsigned getNumFixupKinds() const override {
       return Sparc::NumTargetFixupKinds;
@@ -359,7 +359,7 @@ namespace {
     std::unique_ptr<MCObjectTargetWriter>
     createObjectTargetWriter() const override {
       uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(OSType);
-      return createSparcELFObjectWriter(Is64Bit, HasV9, OSABI);
+      return createSparcELFObjectWriter(Is64Bit, IsV8Plus, OSABI);
     }
   };
 

llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp

@@ -21,11 +21,11 @@ using namespace llvm;
 namespace {
   class SparcELFObjectWriter : public MCELFObjectTargetWriter {
   public:
-    SparcELFObjectWriter(bool Is64Bit, bool HasV9, uint8_t OSABI)
+    SparcELFObjectWriter(bool Is64Bit, bool IsV8Plus, uint8_t OSABI)
         : MCELFObjectTargetWriter(
               Is64Bit, OSABI,
               Is64Bit ? ELF::EM_SPARCV9
-                      : (HasV9 ? ELF::EM_SPARC32PLUS : ELF::EM_SPARC),
+                      : (IsV8Plus ? ELF::EM_SPARC32PLUS : ELF::EM_SPARC),
               /*HasRelocationAddend*/ true) {}
 
     ~SparcELFObjectWriter() override = default;
@@ -148,6 +148,6 @@ bool SparcELFObjectWriter::needsRelocateWithSymbol(const MCValue &,
 }
 
 std::unique_ptr<MCObjectTargetWriter>
-llvm::createSparcELFObjectWriter(bool Is64Bit, bool HasV9, uint8_t OSABI) {
-  return std::make_unique<SparcELFObjectWriter>(Is64Bit, HasV9, OSABI);
+llvm::createSparcELFObjectWriter(bool Is64Bit, bool IsV8Plus, uint8_t OSABI) {
+  return std::make_unique<SparcELFObjectWriter>(Is64Bit, IsV8Plus, OSABI);
 }

llvm/lib/Target/Sparc/MCTargetDesc/SparcMCTargetDesc.cpp

@@ -86,7 +86,7 @@ createSparcMCSubtargetInfo(const Triple &TT, StringRef CPU, StringRef FS) {
 
 static MCTargetStreamer *
 createObjectTargetStreamer(MCStreamer &S, const MCSubtargetInfo &STI) {
-  return new SparcTargetELFStreamer(S);
+  return new SparcTargetELFStreamer(S, STI);
 }
 
 static MCTargetStreamer *createTargetAsmStreamer(MCStreamer &S,

llvm/lib/Target/Sparc/MCTargetDesc/SparcMCTargetDesc.h

@@ -35,7 +35,7 @@ MCAsmBackend *createSparcAsmBackend(const Target &T, const MCSubtargetInfo &STI,
                                     const MCRegisterInfo &MRI,
                                     const MCTargetOptions &Options);
 std::unique_ptr<MCObjectTargetWriter>
-createSparcELFObjectWriter(bool Is64Bit, bool HasV9, uint8_t OSABI);
+createSparcELFObjectWriter(bool Is64Bit, bool IsV8Plus, uint8_t OSABI);
 
 // Defines symbolic names for Sparc v9 ASI tag names.
 namespace SparcASITag {

llvm/lib/Target/Sparc/MCTargetDesc/SparcTargetStreamer.cpp

@@ -12,11 +12,24 @@
 
 #include "SparcTargetStreamer.h"
 #include "SparcInstPrinter.h"
+#include "SparcMCTargetDesc.h"
+#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/MC/MCELFObjectWriter.h"
 #include "llvm/MC/MCRegister.h"
+#include "llvm/MC/MCSubtargetInfo.h"
 #include "llvm/Support/FormattedStream.h"
 
 using namespace llvm;
 
+static unsigned getEFlagsForFeatureSet(const MCSubtargetInfo &STI) {
+  unsigned EFlags = 0;
+
+  if (STI.hasFeature(Sparc::FeatureV8Plus))
+    EFlags |= ELF::EF_SPARC_32PLUS;
+
+  return EFlags;
+}
+
 // pin vtable to this file
 SparcTargetStreamer::SparcTargetStreamer(MCStreamer &S) : MCTargetStreamer(S) {}
 
@@ -38,8 +51,16 @@ void SparcTargetAsmStreamer::emitSparcRegisterScratch(unsigned reg) {
      << ", #scratch\n";
 }
 
-SparcTargetELFStreamer::SparcTargetELFStreamer(MCStreamer &S)
-    : SparcTargetStreamer(S) {}
+SparcTargetELFStreamer::SparcTargetELFStreamer(MCStreamer &S,
+                                               const MCSubtargetInfo &STI)
+    : SparcTargetStreamer(S) {
+  ELFObjectWriter &W = getStreamer().getWriter();
+  unsigned EFlags = W.getELFHeaderEFlags();
+
+  EFlags |= getEFlagsForFeatureSet(STI);
+
+  W.setELFHeaderEFlags(EFlags);
+}
 
 MCELFStreamer &SparcTargetELFStreamer::getStreamer() {
   return static_cast<MCELFStreamer &>(Streamer);

llvm/lib/Target/Sparc/MCTargetDesc/SparcTargetStreamer.h

@@ -40,7 +40,7 @@ class SparcTargetAsmStreamer : public SparcTargetStreamer {
 // This part is for ELF object output
 class SparcTargetELFStreamer : public SparcTargetStreamer {
 public:
-  SparcTargetELFStreamer(MCStreamer &S);
+  SparcTargetELFStreamer(MCStreamer &S, const MCSubtargetInfo &STI);
   MCELFStreamer &getStreamer();
   void emitSparcRegisterIgnore(unsigned reg) override {}
   void emitSparcRegisterScratch(unsigned reg) override {}

llvm/lib/Target/Sparc/Sparc.td

@@ -34,6 +34,9 @@ def FeatureNoFMULS
 def FeatureV9
   : SubtargetFeature<"v9", "IsV9", "true",
                      "Enable SPARC-V9 instructions">;
+def FeatureV8Plus
+  : SubtargetFeature<"v8plus", "IsV8Plus", "true",
+                     "Enable V8+ mode, allowing use of 64-bit V9 instructions in 32-bit code">;
 def FeatureV8Deprecated
   : SubtargetFeature<"deprecated-v8", "UseV8DeprecatedInsts", "true",
                      "Enable deprecated V8 instructions in V9 mode">;

llvm/test/MC/Sparc/elf-sparc-machine-type.s

@@ -1,11 +1,11 @@
 ## Emit correct machine type depending on triple and cpu options.
 ## - `-triple sparc` emits an object of type EM_SPARC;
-## - `-triple sparc -mcpu=v9` emits EM_SPARC32PLUS; and
+## - `-triple sparc -mattr=+v8plus` emits EM_SPARC32PLUS; and
 ## - `-triple sparcv9` emits EM_SPARCV9.
 
-# RUN: llvm-mc -filetype=obj -triple sparc            %s -o - | llvm-readobj -h - | FileCheck --check-prefixes=SPARC       %s
-# RUN: llvm-mc -filetype=obj -triple sparc   -mcpu=v9 %s -o - | llvm-readobj -h - | FileCheck --check-prefixes=SPARC32PLUS %s
-# RUN: llvm-mc -filetype=obj -triple sparcv9          %s -o - | llvm-readobj -h - | FileCheck --check-prefixes=SPARCV9     %s
+# RUN: llvm-mc -filetype=obj -triple sparc                  %s -o - | llvm-readobj -h - | FileCheck --check-prefixes=SPARC       %s
+# RUN: llvm-mc -filetype=obj -triple sparc   -mattr=+v8plus %s -o - | llvm-readobj -h - | FileCheck --check-prefixes=SPARC32PLUS %s
+# RUN: llvm-mc -filetype=obj -triple sparcv9                %s -o - | llvm-readobj -h - | FileCheck --check-prefixes=SPARCV9     %s
 
 # SPARC:       Machine: EM_SPARC (0x2)
 # SPARC32PLUS: Machine: EM_SPARC32PLUS (0x12)