[ELF][PPC64] Synthesize _savegpr[01]_{14..31} and _restgpr[01]_{14..31}

[MaskRay]

Summary

In the 64-bit ELF V2 API Specification: Power Architecture, 2.3.3.1. GPR
Save and Restore Functions defines some special functions which may be
referenced by GCC produced assembly (LLVM does not reference them).

With GCC -Os, when the number of call-saved registers exceeds a certain
threshold, GCC generates _savegpr0_* _restgpr0_* calls and expects the
linker to define them. See
https://sourceware.org/pipermail/binutils/2002-February/017444.html and
https://sourceware.org/pipermail/binutils/2004-August/036765.html . This
is weird because libgcc.a would be the natural place. However, the linker
generation approach has the advantage that the linker can generate
multiple copies to avoid long branch thunks. We don't consider the
advantage significant enough to complicate our trunk implementation, so
we take a simple approach.

• Check whether _savegpr[01]_{14..31} and _restgpr[01]_{14..31} are used
• If yes, assemble the predefined .s and add the object file as LazyObjFile.

[MaskRay]

lld/ELF/Arch/PPC64SaveRest.cpp

62

I should add .hidden as well.

lld/test/ELF/ppc64-savegpr1.s

15

I should change one test to check -shared

[MaskRay]

adjust

[MaskRay]

Better approach.
Synthesize InputSections

[Bdragon28]

lld/ELF/Arch/PPC64.cpp

165 ↗

(On Diff #264459)

The example in the ABI doc was illustrating that you can split it into multiple chunks if you make sure both sides finish off saving the rest of the registers. It's actually cleaner to just have it continue dropping through until the end.

I believe the reason for the ABI doc having the example like it is is probably something to do with r30,r31 save/restore being much more common than full save/restore so binutils ld has a small and a large version.

Since we're not bothering with sticking multiple copies in anyway, it doesn't matter and we can go with the simpler implementation here of not treating r29 differently.

179 ↗

(On Diff #264459)

These are at fixed offsets to catch counting errors in the code above, correct?

[MaskRay]

Simplify _restgpr0_*

lld/ELF/Arch/PPC64.cpp

165 ↗

(On Diff #264459)

Thanks for the comment. Let me simplify _restgpr0_*

This is probably some microarchitectural optimization we don't care much.

179 ↗

(On Diff #264459)

Yes.

[sfertile]

Thanks for implementing this MaskRay. I've left a couple comments, but still need to go through the testing.

lld/ELF/Arch/PPC64.cpp

133 ↗

(On Diff #265335)

Since we are always writing the entire routine into the buffer anyway why not just hard code the array contents so we don't have to compute it at runtime?

143 ↗

(On Diff #265335)

real minor nit: I think the code would be a bit clearer if this check cake outside the lamda: eg

if (!defined.empty())
  addSection(...)

152 ↗

(On Diff #265335)

Does it clutter the code too much to keep track of the correct value in the loop that calls `addOptional' and not have to adjust this later?

[MaskRay]

lld/ELF/Arch/PPC64.cpp

133 ↗

(On Diff #265335)

We need to define symbols _savegpr* and _restgpr*, so a loop is needed. There is little saving if we move instructions alone to a constant array.

143 ↗

(On Diff #265335)

Mostly there are 4 callers. Placing it here saves some code.

152 ↗

(On Diff #265335)

Yes, the alternative approach will clutter the code. It will require 2 loops, with one finding the start point and the second placing instructions and definitions. This post adjustment approach is the simplest I can find.

[sfertile]

lld/ELF/Arch/PPC64.cpp

133 ↗

(On Diff #265335)

The savings mostly come from making the 4 loops we have now (and the 2 that need to be added later for the fpr save/restore routines) nearly identical. We can then write a helper function or lambda and call that 6 time instead of having 6 loops once we add support for _savefpr* and _restfpr* as well. With a minor tweak I believe the helper would also work for the vector save restore routines as well.

Something like:

Helper(uint32_t *Buffer, uint32_t BufferSize, StringRef Prefix) {
  int r = findFirstOf(prefix);  // returns the register number corresponding to the first symbol we need to define.
  // Any referenced symbols are defined, nothing to do.
  if (r == 32)
  return;

  int Value = 0;
  const int Offset = 4 * (r - 14);
  for (r < 32; ++r) {
   Name = FormatName(prefix, r)
    addOptional(Name, Value, defined);
    Value += 4;
  }
  // No need to check if defined is empty becuase we would have returned already if no symbols need to be defiend.
  addSection(Buffer + Offset, Buffer + Size, defined);
}

Its longer and more verbose then one of the for loops, but I think its much easier to follow the logic, and then it only takes 6 lines like:

Helper(savegpr0, ArraySize(savegpr0), "__savegpr0_");

Its more lines of code total, since defining the arrays adds more lines then we save with the replacing the for loops with the helper but I think its much more approachable for a reader.

152 ↗

(On Diff #265335)

I think this approach is simpler in terms of less lines of code, but not necessarily simpler to read or understand.

[MaskRay]

Simplify

lld/ELF/Arch/PPC64.cpp

133 ↗

(On Diff #265335)

Thanks for the suggestion. I have found a way to simplify the code.

[MaskRay]

Simplify with MutableArrayRef<uint32_t>

[MaskRay]

@sfertile Looks good now?

[sfertile]

One comment but otherwise LGTM.

lld/ELF/Arch/PPC64.cpp

125 ↗

(On Diff #265618)

nit: from is always 14 so we don't need it as an argument, we can just always start the loop at 14.

[MaskRay]

Thanks for the review! Will commit soon...

lld/ELF/Arch/PPC64.cpp

125 ↗

(On Diff #265618)

This is reserved for _savevr_20 and _restvr_20 which start from 20 instead of 14..

lld/ELF/Arch/PPC64SaveRest.cpp

+//===- PPC64SaveRest.cpp --------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements some save and restore functions as described by ELF V2
+// ABI to be compatible with GCC. With GCC -Os, when the number of call-saved
+// registers exceeds a certain threshold, GCC generates _savegpr0_* _restgpr0_*
+// calls and expects the linker to define them. See
+// https://sourceware.org/pipermail/binutils/2002-February/017444.html and
+// https://sourceware.org/pipermail/binutils/2004-August/036765.html . This is
+// weird because libgcc.a would be the natural place. However, the linker
+// generation approach has the advantage that the linker can generate multiple
+// copies to avoid long branch thunks. We don't consider the advantage
+// significant enough to complicate our trunk implementation, so we take the
+// simple approach:
+//
+// if such magic symbols are referenced, assemble the predefined .s, and add the
+// object files as LazyObjFile.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Config.h"
+#include "InputFiles.h"
+#include "lld/Common/Memory.h"
+#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCInstrInfo.h"
+#include "llvm/MC/MCObjectFileInfo.h"
+#include "llvm/MC/MCObjectWriter.h"
+#include "llvm/MC/MCParser/MCAsmParser.h"
+#include "llvm/MC/MCParser/MCTargetAsmParser.h"
+#include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSubtargetInfo.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/Support/TargetRegistry.h"
+
+using namespace llvm;
+using namespace lld;
+using namespace lld::elf;
+
+// clang-format off
+/* Generated by:
+awk 'BEGIN{
+print "static constexpr char savegpr0[] = R\"("
+  print ".section .text,\"ax\",@progbits,unique,0"
+  printf ".globl "; for(i=14;i<32;i++) { printf "_savegpr0_" i (i==31?"\n":",") }
+  printf ".hidden "; for(i=14;i<32;i++) { printf "_savegpr0_" i (i==31?"\n":",") }
+  for(i=14;i<32;i++) { print "_savegpr0_" i ": " s "std " i "," (i*8-256) "(1)" }
+  print "std 0,16(1)\nblr"
+
+  print "\n.section .text,\"ax\",@progbits,unique,1"
+  printf ".globl "; for(i=14;i<32;i++) { printf "_restgpr0_" i (i==31?"\n":",") }
+  printf ".hidden "; for(i=14;i<32;i++) { printf "_restgpr0_" i (i==31?"\n":",") }
+  for(i=14;i<29;i++) { print "_restgpr0_" i ": " s "ld " i "," (i*8-256) "(1)" }
+  print "_restgpr0_29: ld 0,16(1)\nld 29,-24(1)\nmtlr 0\nld 30,-16(1)\nld 31,-8(1)\nblr"
+  print "_restgpr0_30: ld 30,-16(1)"
+  print "_restgpr0_31: ld 0,16(1)\nld 31,-8(1)\nmtlr 0\nblr"
+print ")\";\n"
+
+print "static constexpr char savegpr1[] = R\"("
+  print ".section .text,\"ax\",@progbits,unique,0"
+  printf ".globl "; for(i=14;i<32;i++) { printf "_savegpr1_" i (i==31?"\n":",") }
+  printf ".hidden "; for(i=14;i<32;i++) { printf "_savegpr1_" i (i==31?"\n":",") }
+  for(i=14;i<32;i++) { print "_savegpr1_" i ": " s "std " i "," (i*8-256) "(12)" }
+  print "blr"
+
+  print "\n.section .text,\"ax\",@progbits,unique,1"
+  printf ".globl "; for(i=14;i<32;i++) { printf "_restgpr1_" i (i==31?"\n":",") }
+  printf ".hidden "; for(i=14;i<32;i++) { printf "_restgpr1_" i (i==31?"\n":",") }
+  for(i=14;i<32;i++) { print "_restgpr1_" i ": " s "ld " i "," (i*8-256) "(12)" }
+  print "blr"
+print ")\";\n"
+}' /dev/null
+*/
+
+// We could produce function sections and add artificial R_PPC64_NONE
+// relocations to allow --gc-sections to collect unneeded functions. However,
+// that will break --shuffle-sections.
+
+static constexpr char savegpr0[] = R"(
+.section .text,"ax",@progbits,unique,0
+.globl _savegpr0_14,_savegpr0_15,_savegpr0_16,_savegpr0_17,_savegpr0_18,_savegpr0_19,_savegpr0_20,_savegpr0_21,_savegpr0_22,_savegpr0_23,_savegpr0_24,_savegpr0_25,_savegpr0_26,_savegpr0_27,_savegpr0_28,_savegpr0_29,_savegpr0_30,_savegpr0_31
+.hidden _savegpr0_14,_savegpr0_15,_savegpr0_16,_savegpr0_17,_savegpr0_18,_savegpr0_19,_savegpr0_20,_savegpr0_21,_savegpr0_22,_savegpr0_23,_savegpr0_24,_savegpr0_25,_savegpr0_26,_savegpr0_27,_savegpr0_28,_savegpr0_29,_savegpr0_30,_savegpr0_31
+_savegpr0_14: std 14,-144(1)
+_savegpr0_15: std 15,-136(1)
+_savegpr0_16: std 16,-128(1)
+_savegpr0_17: std 17,-120(1)
+_savegpr0_18: std 18,-112(1)
+_savegpr0_19: std 19,-104(1)
+_savegpr0_20: std 20,-96(1)
+_savegpr0_21: std 21,-88(1)
+_savegpr0_22: std 22,-80(1)
+_savegpr0_23: std 23,-72(1)
+_savegpr0_24: std 24,-64(1)
+_savegpr0_25: std 25,-56(1)
+_savegpr0_26: std 26,-48(1)
+_savegpr0_27: std 27,-40(1)
+_savegpr0_28: std 28,-32(1)
+_savegpr0_29: std 29,-24(1)
+_savegpr0_30: std 30,-16(1)
+_savegpr0_31: std 31,-8(1)
+std 0,16(1)
+blr
+
+.section .text,"ax",@progbits,unique,1
+.globl _restgpr0_14,_restgpr0_15,_restgpr0_16,_restgpr0_17,_restgpr0_18,_restgpr0_19,_restgpr0_20,_restgpr0_21,_restgpr0_22,_restgpr0_23,_restgpr0_24,_restgpr0_25,_restgpr0_26,_restgpr0_27,_restgpr0_28,_restgpr0_29,_restgpr0_30,_restgpr0_31
+.hidden _restgpr0_14,_restgpr0_15,_restgpr0_16,_restgpr0_17,_restgpr0_18,_restgpr0_19,_restgpr0_20,_restgpr0_21,_restgpr0_22,_restgpr0_23,_restgpr0_24,_restgpr0_25,_restgpr0_26,_restgpr0_27,_restgpr0_28,_restgpr0_29,_restgpr0_30,_restgpr0_31
+_restgpr0_14: ld 14,-144(1)
+_restgpr0_15: ld 15,-136(1)
+_restgpr0_16: ld 16,-128(1)
+_restgpr0_17: ld 17,-120(1)
+_restgpr0_18: ld 18,-112(1)
+_restgpr0_19: ld 19,-104(1)
+_restgpr0_20: ld 20,-96(1)
+_restgpr0_21: ld 21,-88(1)
+_restgpr0_22: ld 22,-80(1)
+_restgpr0_23: ld 23,-72(1)
+_restgpr0_24: ld 24,-64(1)
+_restgpr0_25: ld 25,-56(1)
+_restgpr0_26: ld 26,-48(1)
+_restgpr0_27: ld 27,-40(1)
+_restgpr0_28: ld 28,-32(1)
+_restgpr0_29: ld 0,16(1)
+ld 29,-24(1)
+mtlr 0
+ld 30,-16(1)
+ld 31,-8(1)
+blr
+_restgpr0_30: ld 30,-16(1)
+_restgpr0_31: ld 0,16(1)
+ld 31,-8(1)
+mtlr 0
+blr
+)";
+
+static constexpr char savegpr1[] = R"(
+.section .text,"ax",@progbits,unique,0
+.globl _savegpr1_14,_savegpr1_15,_savegpr1_16,_savegpr1_17,_savegpr1_18,_savegpr1_19,_savegpr1_20,_savegpr1_21,_savegpr1_22,_savegpr1_23,_savegpr1_24,_savegpr1_25,_savegpr1_26,_savegpr1_27,_savegpr1_28,_savegpr1_29,_savegpr1_30,_savegpr1_31
+.hidden _savegpr1_14,_savegpr1_15,_savegpr1_16,_savegpr1_17,_savegpr1_18,_savegpr1_19,_savegpr1_20,_savegpr1_21,_savegpr1_22,_savegpr1_23,_savegpr1_24,_savegpr1_25,_savegpr1_26,_savegpr1_27,_savegpr1_28,_savegpr1_29,_savegpr1_30,_savegpr1_31
+_savegpr1_14: std 14,-144(12)
+_savegpr1_15: std 15,-136(12)
+_savegpr1_16: std 16,-128(12)
+_savegpr1_17: std 17,-120(12)
+_savegpr1_18: std 18,-112(12)
+_savegpr1_19: std 19,-104(12)
+_savegpr1_20: std 20,-96(12)
+_savegpr1_21: std 21,-88(12)
+_savegpr1_22: std 22,-80(12)
+_savegpr1_23: std 23,-72(12)
+_savegpr1_24: std 24,-64(12)
+_savegpr1_25: std 25,-56(12)
+_savegpr1_26: std 26,-48(12)
+_savegpr1_27: std 27,-40(12)
+_savegpr1_28: std 28,-32(12)
+_savegpr1_29: std 29,-24(12)
+_savegpr1_30: std 30,-16(12)
+_savegpr1_31: std 31,-8(12)
+blr
+
+.section .text,"ax",@progbits,unique,1
+.globl _restgpr1_14,_restgpr1_15,_restgpr1_16,_restgpr1_17,_restgpr1_18,_restgpr1_19,_restgpr1_20,_restgpr1_21,_restgpr1_22,_restgpr1_23,_restgpr1_24,_restgpr1_25,_restgpr1_26,_restgpr1_27,_restgpr1_28,_restgpr1_29,_restgpr1_30,_restgpr1_31
+.hidden _restgpr1_14,_restgpr1_15,_restgpr1_16,_restgpr1_17,_restgpr1_18,_restgpr1_19,_restgpr1_20,_restgpr1_21,_restgpr1_22,_restgpr1_23,_restgpr1_24,_restgpr1_25,_restgpr1_26,_restgpr1_27,_restgpr1_28,_restgpr1_29,_restgpr1_30,_restgpr1_31
+_restgpr1_14: ld 14,-144(12)
+_restgpr1_15: ld 15,-136(12)
+_restgpr1_16: ld 16,-128(12)
+_restgpr1_17: ld 17,-120(12)
+_restgpr1_18: ld 18,-112(12)
+_restgpr1_19: ld 19,-104(12)
+_restgpr1_20: ld 20,-96(12)
+_restgpr1_21: ld 21,-88(12)
+_restgpr1_22: ld 22,-80(12)
+_restgpr1_23: ld 23,-72(12)
+_restgpr1_24: ld 24,-64(12)
+_restgpr1_25: ld 25,-56(12)
+_restgpr1_26: ld 26,-48(12)
+_restgpr1_27: ld 27,-40(12)
+_restgpr1_28: ld 28,-32(12)
+_restgpr1_29: ld 29,-24(12)
+_restgpr1_30: ld 30,-16(12)
+_restgpr1_31: ld 31,-8(12)
+blr
+)";
+
+// clang-format on
+
+LazyObjFile *elf::getPPC64SaveRestFile(StringRef name) {
+  const char *source;
+  if (name == "savegpr0")
+    source = savegpr0;
+  else if (name == "savegpr1")
+    source = savegpr1;
+  else
+    assert(0 && "invalid name");
+
+  StringRef tripleName = config->isLE ? "powerpc64le-unknown-linux-gnu"
+                                      : "powerpc64-unknown-linux-gnu";
+  Triple triple(tripleName);
+  std::string err;
+  const Target *target = TargetRegistry::lookupTarget("", triple, err);
+  if (!target)
+    return nullptr;
+  std::unique_ptr<MemoryBuffer> buffer = MemoryBuffer::getMemBuffer(source);
+  SourceMgr mgr;
+  mgr.AddNewSourceBuffer(std::move(buffer), SMLoc());
+
+  MCTargetOptions mcOptions;
+  std::unique_ptr<MCRegisterInfo> mri(target->createMCRegInfo(tripleName));
+  std::unique_ptr<MCAsmInfo> mai(
+      target->createMCAsmInfo(*mri, tripleName, mcOptions));
+  MCObjectFileInfo mofi;
+  MCContext ctx(mai.get(), mri.get(), &mofi, &mgr, &mcOptions);
+  mofi.InitMCObjectFileInfo(triple, true, ctx, false);
+  std::unique_ptr<MCInstrInfo> mcii(target->createMCInstrInfo());
+  std::unique_ptr<MCSubtargetInfo> sti(
+      target->createMCSubtargetInfo(tripleName, "", ""));
+
+  SmallString<0> buf;
+  raw_svector_ostream os(buf);
+  std::unique_ptr<MCCodeEmitter> ce(
+      target->createMCCodeEmitter(*mcii, *mri, ctx));
+  MCAsmBackend *mab = target->createMCAsmBackend(*sti, *mri, mcOptions);
+  std::unique_ptr<MCStreamer> str(target->createMCObjectStreamer(
+      triple, ctx, std::unique_ptr<MCAsmBackend>(mab),
+      mab->createObjectWriter(os), std::move(ce), *sti,
+      /*RelaxAll=*/false, /*IncrementalLinkerCompatible=*/false,
+      /*DWARFMustBeAtTheEnd=*/false));
+
+  std::unique_ptr<MCAsmParser> parser(createMCAsmParser(mgr, ctx, *str, *mai));
+  std::unique_ptr<MCTargetAsmParser> tap(
+      target->createMCAsmParser(*sti, *parser, *mcii, mcOptions));
+  parser->setTargetParser(*tap);
+  if (parser->Run(false))
+    return nullptr;
+
+  auto *mb = make<std::unique_ptr<MemoryBuffer>>(
+      MemoryBuffer::getMemBufferCopy(os.str()));
+  return make<LazyObjFile>(**mb, "", 0);
+}

lld/ELF/CMakeLists.txt

add_lld_library(lldELF
   Arch/ARM.cpp
   Arch/AVR.cpp
   Arch/Hexagon.cpp
   Arch/Mips.cpp
   Arch/MipsArchTree.cpp
   Arch/MSP430.cpp
   Arch/PPC.cpp
   Arch/PPC64.cpp
+  Arch/PPC64SaveRest.cpp
   Arch/RISCV.cpp
   Arch/SPARCV9.cpp
   Arch/X86.cpp
   Arch/X86_64.cpp
   ARMErrataFix.cpp
   CallGraphSort.cpp
   DWARF.cpp
   Driver.cpp
add_lld_library(lldELF
   ${LLVM_TARGETS_TO_BUILD}
   BinaryFormat
   BitWriter
   Core
   DebugInfoDWARF
   Demangle
   LTO
   MC
+  MCParser
   Object
   Option
   Passes
   Support
 
   LINK_LIBS
   lldCommon
   ${LLVM_PTHREAD_LIB}
 
   DEPENDS
   ELFOptionsTableGen
   ${tablegen_deps}
   )

lld/ELF/Driver.cpp

template <class ELFT> void LinkerDriver::link(opt::InputArgList &args) {
   // add files to the link, via autolinking, these files are always
   // appended to the Files vector.
   {
     llvm::TimeTraceScope timeScope("Parse input files");
     for (size_t i = 0; i < files.size(); ++i)
       parseFile(files[i]);
   }
 
+  if (config->emachine == EM_PPC64) {
+    bool savegpr0 = false, savegpr1 = false;
+    char name[32];
+    for (int i = 14; i < 32; ++i) {
+      format("_savegpr0_%d", i).snprint(name, sizeof(name));
+      if (symtab->find(name))
+        savegpr0 = true;
+      format("_restgpr0_%d", i).snprint(name, sizeof(name));
+      if (symtab->find(name))
+        savegpr0 = true;
+
+      format("_savegpr1_%d", i).snprint(name, sizeof(name));
+      if (symtab->find(name))
+        savegpr1 = true;
+      format("_restgpr1_%d", i).snprint(name, sizeof(name));
+      if (symtab->find(name))
+        savegpr1 = true;
+    }
+    if (savegpr0)
+      if (LazyObjFile *file = getPPC64SaveRestFile("savegpr0"))
+        parseFile(file);
+    if (savegpr1)
+      if (LazyObjFile *file = getPPC64SaveRestFile("savegpr1"))
+        parseFile(file);
+  }
+
   // Now that we have every file, we can decide if we will need a
   // dynamic symbol table.
   // We need one if we were asked to export dynamic symbols or if we are
   // producing a shared library.
   // We also need one if any shared libraries are used and for pie executables
   // (probably because the dynamic linker needs it).
   config->hasDynSymTab =
       !sharedFiles.empty() || config->isPic || config->exportDynamic;

lld/ELF/InputFiles.h

InputFile *createObjectFile(MemoryBufferRef mb, StringRef archiveName = "",
                             uint64_t offsetInArchive = 0);
 
 inline bool isBitcode(MemoryBufferRef mb) {
   return identify_magic(mb.getBuffer()) == llvm::file_magic::bitcode;
 }
 
 std::string replaceThinLTOSuffix(StringRef path);
 
+LazyObjFile *getPPC64SaveRestFile(StringRef name);
+
 extern std::vector<ArchiveFile *> archiveFiles;
 extern std::vector<BinaryFile *> binaryFiles;
 extern std::vector<BitcodeFile *> bitcodeFiles;
 extern std::vector<LazyObjFile *> lazyObjFiles;
 extern std::vector<InputFile *> objectFiles;
 extern std::vector<SharedFile *> sharedFiles;
 
 } // namespace elf
 } // namespace lld
 
 #endif

lld/test/ELF/ppc64-savegpr0.s

+# REQUIRES: ppc
+## _savegpr0_{14..31} and _restgpr0_{14..31} can be synthesized.
+
+# RUN: llvm-mc -filetype=obj -triple=ppc64 %s -o %t14.o
+# RUN: ld.lld %t14.o -o %t14
+# RUN: llvm-objdump -d --no-show-raw-insn %t14 | FileCheck %s
+# RUN: llvm-readelf -s %t14 | FileCheck --check-prefix=NM %s
+
+# RUN: echo 'bl _restgpr0_14' | llvm-mc -filetype=obj -triple=ppc64le - -o %t14r.o
+# RUN: ld.lld -shared %t14r.o -o %t14r.so
+# RUN: llvm-objdump -d --no-show-raw-insn %t14r.so | FileCheck %s
+
+# RUN: echo 'bl _savegpr0_31' | llvm-mc -filetype=obj -triple=ppc64le - -o %t31.o
+# RUN: ld.lld %t31.o -o %t31
+# RUN: llvm-objdump -d --no-show-raw-insn %t31 | FileCheck %s
+
+# RUN: echo 'bl _savegpr0_32' | llvm-mc -filetype=obj -triple=ppc64le - -o %t32.o
+# RUN: not ld.lld %t32.o -o /dev/null
+
+# NM: NOTYPE LOCAL HIDDEN {{.*}} _savegpr0_14
+
+# CHECK:      <_savegpr0_14>:
+# CHECK-NEXT:   std 14, -144(1)
+# CHECK-EMPTY:
+# CHECK-NEXT: <_savegpr0_15>:
+# CHECK-NEXT:   std 15, -136(1)
+# CHECK-EMPTY:
+
+# CHECK:      <_savegpr0_31>:
+# CHECK-NEXT:   std 31, -8(1)
+# CHECK-NEXT:   std 0, 16(1)
+# CHECK-NEXT:   blr
+# CHECK-EMPTY:
+# CHECK-NEXT: <_restgpr0_14>:
+# CHECK-NEXT:   ld 14, -144(1)
+# CHECK-EMPTY:
+# CHECK-NEXT: <_restgpr0_15>:
+# CHECK-NEXT:   ld 15, -136(1)
+# CHECK-EMPTY:
+
+# CHECK:      <_restgpr0_29>:
+# CHECK-NEXT:   ld 0, 16(1)
+# CHECK-NEXT:   ld 29, -24(1)
+# CHECK-NEXT:   mtlr 0
+# CHECK-NEXT:   ld 30, -16(1)
+# CHECK-NEXT:   ld 31, -8(1)
+# CHECK-NEXT:   blr
+# CHECK-EMPTY:
+# CHECK-NEXT: <_restgpr0_30>:
+# CHECK-NEXT:   ld 30, -16(1)
+# CHECK-EMPTY:
+# CHECK-NEXT: <_restgpr0_31>:
+# CHECK-NEXT:   ld 0, 16(1)
+# CHECK-NEXT:   ld 31, -8(1)
+# CHECK-NEXT:   mtlr 0
+# CHECK-NEXT:   blr
+
+.globl _start
+_start:
+  bl _savegpr0_14

lld/test/ELF/ppc64-savegpr1.s

+# REQUIRES: ppc
+## _savegpr1_{14..31} and _restgpr1_{14..31} can be synthesized.
+
+# RUN: llvm-mc -filetype=obj -triple=ppc64 %s -o %t14.o
+# RUN: ld.lld %t14.o -o %t14
+# RUN: llvm-objdump -d --no-show-raw-insn %t14 | FileCheck %s
+
+# RUN: echo 'bl _restgpr1_14' | llvm-mc -filetype=obj -triple=ppc64le - -o %t14r.o
+# RUN: ld.lld -shared %t14r.o -o %t14r.so
+# RUN: llvm-objdump -d --no-show-raw-insn %t14r.so | FileCheck %s
+
+# RUN: echo 'bl _savegpr1_31' | llvm-mc -filetype=obj -triple=ppc64le - -o %t31.o
+# RUN: ld.lld %t31.o -o %t31
+# RUN: llvm-objdump -d --no-show-raw-insn %t31 | FileCheck %s
+
+# RUN: echo 'bl _savegpr1_32' | llvm-mc -filetype=obj -triple=ppc64le - -o %t32.o
+# RUN: not ld.lld %t32.o -o /dev/null
+
+# NM: NOTYPE LOCAL HIDDEN {{.*}} _savegpr1_14
+
+# CHECK:      <_savegpr1_14>:
+# CHECK-NEXT:   std 14, -144(12)
+# CHECK-EMPTY:
+# CHECK-NEXT: <_savegpr1_15>:
+# CHECK-NEXT:   std 15, -136(12)
+# CHECK-EMPTY:
+
+# CHECK:      <_savegpr1_31>:
+# CHECK-NEXT:   std 31, -8(12)
+# CHECK-NEXT:   blr
+# CHECK-EMPTY:
+# CHECK-NEXT: <_restgpr1_14>:
+# CHECK-NEXT:   ld 14, -144(12)
+# CHECK-EMPTY:
+# CHECK-NEXT: <_restgpr1_15>:
+# CHECK-NEXT:   ld 15, -136(12)
+# CHECK-EMPTY:
+
+# CHECK:      <_restgpr1_31>:
+# CHECK-NEXT:   ld 31, -8(12)
+# CHECK-NEXT:   blr
+
+.globl _start
+_start:
+  bl _savegpr1_14

llvm/utils/gn/secondary/lld/ELF/BUILD.gn

sources = [
     "Arch/ARM.cpp",
     "Arch/AVR.cpp",
     "Arch/Hexagon.cpp",
     "Arch/MSP430.cpp",
     "Arch/Mips.cpp",
     "Arch/MipsArchTree.cpp",
     "Arch/PPC.cpp",
     "Arch/PPC64.cpp",
+    "Arch/PPC64SaveRest.cpp",
     "Arch/RISCV.cpp",
     "Arch/SPARCV9.cpp",
     "Arch/X86.cpp",
     "Arch/X86_64.cpp",
     "CallGraphSort.cpp",
     "DWARF.cpp",
     "Driver.cpp",
     "DriverUtils.cpp",