[PowerPC64] adds ABI parsing when specified on target triple

[adalava]

Summary

LLVM supports OpenPower ABI ELFv2 when argument "-mabi=elfv2" if used on clang, as default ABI is ELFv1. FreeBSD support for PowerPC64 ELFv2 ABI with LLVM is in progress[1], so this patch adds an alternative way to specify ELFv2 ABI on target triple [2].

The following results are expected:

ELFv1 when using:
-target powerpc64-unknown-freebsd12.0
-target powerpc64-unknown-freebsd12.0 -mabi=elfv1
-target powerpc64-unknown-freebsd12.0-elfv1

ELFv2 when using:
-target powerpc64-unknown-freebsd12.0 -mabi=elfv2
-target powerpc64-unknown-freebsd12.0-elfv2

[1] https://wiki.freebsd.org/powerpc/llvm-elfv2
[2] https://clang.llvm.org/docs/CrossCompilation.html

[MaskRay]

clang/lib/Basic/Targets/PPC.h

382 ↗

(On Diff #199620)

Have you researched how GNU as chooses the default ABI?

I think the change may break some Linux ppc64le users as they expect the default elfv2.

[MaskRay]

clang/lib/Basic/Targets/PPC.h

382 ↗

(On Diff #199620)

Sorry, it won't :) Then I think it is fine.

[MaskRay]

llvm/lib/Target/PowerPC/PPCTargetMachine.cpp

217 ↗

(On Diff #199620)

The initial word should be capitalized and the sentence should end with a period. At least this part of the comment (if ELFv2 on target triple ) is redundant. I don't know if the other half powerpc64-unknown-freebsd12.0-elfv2 is useful...

[adalava]

clang/lib/Basic/Targets/PPC.h

382 ↗

(On Diff #199620)

I didn't look the code, but behavior on GNU is the same as LLVM too:

• powerpc64-* and elfv2 if "powerpc64le-*" and last

I found setting the ABI value here is useless so I decided to remove to keep it consistent with it's "sister" X86 class and checked that no tests are broken after this, but would be nice if someone with more LLVm experience could give another look.

[adalava]

• remove redundant comment

[adalava]

llvm/lib/Target/PowerPC/PPCTargetMachine.cpp

217 ↗

(On Diff #199620)

yeah, sounds like code clears explains itself. I'm removing the comment.

[MaskRay]

Will FreeBSD 13 or future releases support ELFv1? If not, it may be cleaner to not invent -elfv2 -elfv1 triples, but rather dispatch on the major version, e.g. powerpc64-unknown-freebsd13.0 could mean ELFv2.

[adalava]

In D61950#1504169, @MaskRay wrote:

Will FreeBSD 13 or future releases support ELFv1? If not, it may be cleaner to not invent -elfv2 -elfv1 triples, but rather dispatch on the major version, e.g. powerpc64-unknown-freebsd13.0 could mean ELFv2.

Invent -elfv2 -elfv1 and make it used by default is not the goal here but add ABI target triple support. Discussions at llvm IRC channel shown that provide ABI in target triple is more acceptable than using -mabi=elfv2. This patch is for when you want force an ABI other than default one (that was based on <arch>, <os> or <os_version>)

For FreeBSD, yes, the default ABI will be decided based on OS version on triple powerpc64-unknown-freebsd<os_version>. However, there's no agreement on what will be that <os_version>. Even if it's decided that RELEASE/13.0 will be ELFv2, CURRENT/Development/13.0 is ELFv1, LLVM can't assume 13.0 is ELFv2 at this moment or it will break users.

So, during the transition period, developers could use TARGET_ABI variable to build the FreeBSD PPC64 ELFv2 version. As example, building FreeBSD with make TARGET=powerpc TARGET_ARCH=powerpc64 TARGET_ABI=elfv2, where it's expected to form a target triple like powerpc64-unknown-freebsd13.0-elfv2, based on "<arch><sub>-<vendor>-<sys>-<abi>" definition. That is passed right away to clang.

If it's not possible, we would have to patch FreeBSD makefiles to not use TARGET_ABI variable value when TARGET_ARCH is powerpc64, and append -mabi=elfv2 instead. This sounds feasible, however clang running on final ELFv2 userland won't know it's on ELFv2 and users will need to specify -mabi=elfv2 and CFLAGS/CXXFLAGS to compile applications. This is unfeasible, specially for FreeBSD ports, as many packages didn't handle these variables correctly.

[MaskRay]

Thanks for the explanation!

[MaskRay]

Reordered the code a bit and committed for you...

[MaskRay]

@adalava You need to run both check-llvm and check-clang, but it was my fault that I hadn't done this before committing...
Two clang tests failed (http://lab.llvm.org:8011/builders/clang-atom-d525-fedora-rel/builds/24521) It should have been fixed by rC361365

cfe/trunk/lib/Basic/Targets/PPC.h

public:
   PPC64TargetInfo(const llvm::Triple &Triple, const TargetOptions &Opts)
       : PPCTargetInfo(Triple, Opts) {
     LongWidth = LongAlign = PointerWidth = PointerAlign = 64;
     IntMaxType = SignedLong;
     Int64Type = SignedLong;
 
     if ((Triple.getArch() == llvm::Triple::ppc64le)) {
       resetDataLayout("e-m:e-i64:64-n32:64");
-      ABI = "elfv2";
     } else {
       resetDataLayout("E-m:e-i64:64-n32:64");
-      ABI = "elfv1";
     }
 
-    switch (getTriple().getOS()) {
+    switch (Triple.getOS()) {
     case llvm::Triple::FreeBSD:
       LongDoubleWidth = LongDoubleAlign = 64;
       LongDoubleFormat = &llvm::APFloat::IEEEdouble();
       break;
     case llvm::Triple::AIX:
       // FIXME: -mlong-double-128 is not yet supported on AIX.
       LongDoubleWidth = LongDoubleAlign = 64;
       LongDoubleFormat = &llvm::APFloat::IEEEdouble();

llvm/trunk/include/llvm/ADT/Triple.h

enum EnvironmentType {
     GNUABIN32,
     GNUABI64,
     GNUEABI,
     GNUEABIHF,
     GNUX32,
     CODE16,
     EABI,
     EABIHF,
+    ELFv1,
+    ELFv2,
     Android,
     Musl,
     MuslEABI,
     MuslEABIHF,
 
     MSVC,
     Itanium,
     Cygnus,

llvm/trunk/lib/Support/Triple.cpp

StringRef Triple::getEnvironmentTypeName(EnvironmentType Kind) {
   case GNUABIN32: return "gnuabin32";
   case GNUABI64: return "gnuabi64";
   case GNUEABIHF: return "gnueabihf";
   case GNUEABI: return "gnueabi";
   case GNUX32: return "gnux32";
   case CODE16: return "code16";
   case EABI: return "eabi";
   case EABIHF: return "eabihf";
+  case ELFv1: return "elfv1";
+  case ELFv2: return "elfv2";
   case Android: return "android";
   case Musl: return "musl";
   case MuslEABI: return "musleabi";
   case MuslEABIHF: return "musleabihf";
   case MSVC: return "msvc";
   case Itanium: return "itanium";
   case Cygnus: return "cygnus";
   case CoreCLR: return "coreclr";
return StringSwitch<Triple::OSType>(OSName)
     .StartsWith("emscripten", Triple::Emscripten)
     .Default(Triple::UnknownOS);
 }
 
 static Triple::EnvironmentType parseEnvironment(StringRef EnvironmentName) {
   return StringSwitch<Triple::EnvironmentType>(EnvironmentName)
     .StartsWith("eabihf", Triple::EABIHF)
     .StartsWith("eabi", Triple::EABI)
+    .StartsWith("elfv1", Triple::ELFv1)
+    .StartsWith("elfv2", Triple::ELFv2)
     .StartsWith("gnuabin32", Triple::GNUABIN32)
     .StartsWith("gnuabi64", Triple::GNUABI64)
     .StartsWith("gnueabihf", Triple::GNUEABIHF)
     .StartsWith("gnueabi", Triple::GNUEABI)
     .StartsWith("gnux32", Triple::GNUX32)
     .StartsWith("code16", Triple::CODE16)
     .StartsWith("gnu", Triple::GNU)
     .StartsWith("android", Triple::Android)

llvm/trunk/lib/Target/PowerPC/PPCTargetMachine.cpp

static PPCTargetMachine::PPCABI computeTargetABI(const Triple &TT,
 
   if (TT.isMacOSX())
     return PPCTargetMachine::PPC_ABI_UNKNOWN;
 
   switch (TT.getArch()) {
   case Triple::ppc64le:
     return PPCTargetMachine::PPC_ABI_ELFv2;
   case Triple::ppc64:
+    if (TT.getEnvironment() == llvm::Triple::ELFv2)
+      return PPCTargetMachine::PPC_ABI_ELFv2;
     return PPCTargetMachine::PPC_ABI_ELFv1;
   default:
     return PPCTargetMachine::PPC_ABI_UNKNOWN;
   }
 }
 
 static Reloc::Model getEffectiveRelocModel(const Triple &TT,
                                            Optional<Reloc::Model> RM) {

llvm/trunk/test/CodeGen/PowerPC/ppc64-elf-abi.ll

 ; RUN: llc -verify-machineinstrs -mtriple=powerpc64-unknown-linux-gnu < %s | FileCheck %s -check-prefix=CHECK-ELFv1
 ; RUN: llc -verify-machineinstrs -mtriple=powerpc64-unknown-linux-gnu -target-abi elfv1 < %s | FileCheck %s -check-prefix=CHECK-ELFv1
 ; RUN: llc -verify-machineinstrs -mtriple=powerpc64-unknown-linux-gnu -target-abi elfv2 < %s | FileCheck %s -check-prefix=CHECK-ELFv2
 ; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu < %s | FileCheck %s -check-prefix=CHECK-ELFv2
 ; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu -target-abi elfv1 < %s | FileCheck %s -check-prefix=CHECK-ELFv1
 ; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu -target-abi elfv2 < %s | FileCheck %s -check-prefix=CHECK-ELFv2
 
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64-unknown-freebsd < %s | FileCheck %s -check-prefix=CHECK-ELFv1
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64-unknown-freebsd -target-abi elfv1 < %s | FileCheck %s -check-prefix=CHECK-ELFv1
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64-unknown-freebsd -target-abi elfv2 < %s | FileCheck %s -check-prefix=CHECK-ELFv2
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64-unknown-freebsd-elfv1  < %s | FileCheck %s -check-prefix=CHECK-ELFv1
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64-unknown-freebsd-elfv2  < %s | FileCheck %s -check-prefix=CHECK-ELFv2
+
 ; CHECK-ELFv2: .abiversion 2
 ; CHECK-ELFv1-NOT: .abiversion 2
-