[llvm-objdump][AMDGPU] Detect CPU string

AMDGPU ISA isn't backwards compatible and hence -mcpu must always be specified during disassembly.
However, the AMDGPU target CPU is stored in e_flags in the ELF object.

This patch allows targets to implement CPU string detection, and also implements it for AMDGPU by looking at e_flags.

Reviewed By: scott.linder

Differential Revision: https://reviews.llvm.org/D84519

Author: Ronak Chauhan

llvm/include/llvm/Object/ELFObjectFile.h

@@ -86,6 +86,10 @@ class ELFObjectFileBase : public ObjectFile {
 
   SubtargetFeatures getRISCVFeatures() const;
 
+  Optional<StringRef> tryGetCPUName() const override;
+
+  StringRef getAMDGPUCPUName() const;
+
   void setARMSubArch(Triple &TheTriple) const override;
 
   virtual uint16_t getEType() const = 0;

llvm/include/llvm/Object/ObjectFile.h

@@ -327,6 +327,7 @@ class ObjectFile : public SymbolicFile {
   virtual StringRef getFileFormatName() const = 0;
   virtual Triple::ArchType getArch() const = 0;
   virtual SubtargetFeatures getFeatures() const = 0;
+  virtual Optional<StringRef> tryGetCPUName() const { return None; };
   virtual void setARMSubArch(Triple &TheTriple) const { }
   virtual Expected<uint64_t> getStartAddress() const {
     return errorCodeToError(object_error::parse_failed);

llvm/lib/Object/ELFObjectFile.cpp

@@ -355,6 +355,117 @@ SubtargetFeatures ELFObjectFileBase::getFeatures() const {
   }
 }
 
+Optional<StringRef> ELFObjectFileBase::tryGetCPUName() const {
+  switch (getEMachine()) {
+  case ELF::EM_AMDGPU:
+    return getAMDGPUCPUName();
+  default:
+    return None;
+  }
+}
+
+StringRef ELFObjectFileBase::getAMDGPUCPUName() const {
+  assert(getEMachine() == ELF::EM_AMDGPU);
+  unsigned CPU = getPlatformFlags() & ELF::EF_AMDGPU_MACH;
+
+  switch (CPU) {
+  // Radeon HD 2000/3000 Series (R600).
+  case ELF::EF_AMDGPU_MACH_R600_R600:
+    return "r600";
+  case ELF::EF_AMDGPU_MACH_R600_R630:
+    return "r630";
+  case ELF::EF_AMDGPU_MACH_R600_RS880:
+    return "rs880";
+  case ELF::EF_AMDGPU_MACH_R600_RV670:
+    return "rv670";
+
+  // Radeon HD 4000 Series (R700).
+  case ELF::EF_AMDGPU_MACH_R600_RV710:
+    return "rv710";
+  case ELF::EF_AMDGPU_MACH_R600_RV730:
+    return "rv730";
+  case ELF::EF_AMDGPU_MACH_R600_RV770:
+    return "rv770";
+
+  // Radeon HD 5000 Series (Evergreen).
+  case ELF::EF_AMDGPU_MACH_R600_CEDAR:
+    return "cedar";
+  case ELF::EF_AMDGPU_MACH_R600_CYPRESS:
+    return "cypress";
+  case ELF::EF_AMDGPU_MACH_R600_JUNIPER:
+    return "juniper";
+  case ELF::EF_AMDGPU_MACH_R600_REDWOOD:
+    return "redwood";
+  case ELF::EF_AMDGPU_MACH_R600_SUMO:
+    return "sumo";
+
+  // Radeon HD 6000 Series (Northern Islands).
+  case ELF::EF_AMDGPU_MACH_R600_BARTS:
+    return "barts";
+  case ELF::EF_AMDGPU_MACH_R600_CAICOS:
+    return "caicos";
+  case ELF::EF_AMDGPU_MACH_R600_CAYMAN:
+    return "cayman";
+  case ELF::EF_AMDGPU_MACH_R600_TURKS:
+    return "turks";
+
+  // AMDGCN GFX6.
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX600:
+    return "gfx600";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX601:
+    return "gfx601";
+
+  // AMDGCN GFX7.
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX700:
+    return "gfx700";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX701:
+    return "gfx701";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX702:
+    return "gfx702";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX703:
+    return "gfx703";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX704:
+    return "gfx704";
+
+  // AMDGCN GFX8.
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX801:
+    return "gfx801";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX802:
+    return "gfx802";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX803:
+    return "gfx803";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX810:
+    return "gfx810";
+
+  // AMDGCN GFX9.
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX900:
+    return "gfx900";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX902:
+    return "gfx902";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX904:
+    return "gfx904";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX906:
+    return "gfx906";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX908:
+    return "gfx908";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX909:
+    return "gfx909";
+
+  // AMDGCN GFX10.
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX1010:
+    return "gfx1010";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX1011:
+    return "gfx1011";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX1012:
+    return "gfx1012";
+  case ELF::EF_AMDGPU_MACH_AMDGCN_GFX1030:
+    return "gfx1030";
+
+  default:
+    llvm_unreachable("Unknown EF_AMDGPU_MACH value");
+  }
+}
+
 // FIXME Encode from a tablegen description or target parser.
 void ELFObjectFileBase::setARMSubArch(Triple &TheTriple) const {
   if (TheTriple.getSubArch() != Triple::NoSubArch)

llvm/test/tools/llvm-objdump/ELF/AMDGPU/subtarget.ll

@@ -0,0 +1,83 @@
+define amdgpu_kernel void @test_kernel() {
+  ret void
+}
+
+; Test subtarget detection. Disassembly is only supported for GFX8 and beyond.
+;
+; ----------------------------------GFX10--------------------------------------
+;
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx1030 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx1030 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt
+
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx1012 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx1012 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt
+
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx1011 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx1011 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt
+
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx1010 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx1010 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt
+
+
+; ----------------------------------GFX9---------------------------------------
+;
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx909 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx909 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt
+
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx908 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx908 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt
+
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx906 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx906 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt
+
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx904 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx904 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt
+
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx902 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx902 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt
+
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx900 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx900 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt
+
+
+; ----------------------------------GFX8---------------------------------------
+;
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx810 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx810 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt
+
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx803 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx803 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt
+
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx802 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx802 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt
+
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx801 -filetype=obj -O0 -o %t.o %s
+; RUN: llvm-objdump -D --arch-name=amdgcn --mcpu=gfx801 %t.o > %t-specify.txt
+; RUN: llvm-objdump -D %t.o > %t-detect.txt
+; RUN: diff %t-specify.txt %t-detect.txt

llvm/tools/llvm-objdump/llvm-objdump.cpp

@@ -2170,6 +2170,10 @@ static void disassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
   if (!AsmInfo)
     reportError(Obj->getFileName(),
                 "no assembly info for target " + TripleName);
+
+  if (MCPU.empty())
+    MCPU = Obj->tryGetCPUName().getValueOr("").str();
+
   std::unique_ptr<const MCSubtargetInfo> STI(
       TheTarget->createMCSubtargetInfo(TripleName, MCPU, Features.getString()));
   if (!STI)