[JITLink][ELF][ppc64] Add skeleton ppc64 support and ELF/ppc64 JITLink backend.

This patch introduces a skeleton JITLink ppc64 support header and ELF/ppc64
backend. No relocations are supported in this initial version, but given a
program requiring no relocations (e.g. one that just returns a constant value
from main) the new backend is able to construct a LinkGraph from a ppc64 ELF
relocatable object, and the llvm-jitlink tool is able to execute it.

This commit should also serve as a good example of how to introduce a JITLink
backend for a new architecture.

Reviewed By: sgraenitz, v.g.vassilev, vchuravy, nemanjai, jain98, MaskRay

Differential Revision: https://reviews.llvm.org/D148192

Author: lhames

llvm/include/llvm/ExecutionEngine/JITLink/ELF_ppc64.h

@@ -0,0 +1,50 @@
+//===------ ELF_ppc64.h - JIT link functions for ELF/ppc64 ------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// jit-link functions for ELF/ppc64{le}.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_JITLINK_ELF_PPC64_H
+#define LLVM_EXECUTIONENGINE_JITLINK_ELF_PPC64_H
+
+#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+
+namespace llvm::jitlink {
+
+/// Create a LinkGraph from an ELF/ppc64 relocatable object.
+///
+/// Note: The graph does not take ownership of the underlying buffer, nor copy
+/// its contents. The caller is responsible for ensuring that the object buffer
+/// outlives the graph.
+///
+/// WARNING: The big-endian backend has not been tested yet.
+Expected<std::unique_ptr<LinkGraph>>
+createLinkGraphFromELFObject_ppc64(MemoryBufferRef ObjectBuffer);
+
+/// Create a LinkGraph from an ELF/ppc64le relocatable object.
+///
+/// Note: The graph does not take ownership of the underlying buffer, nor copy
+/// its contents. The caller is responsible for ensuring that the object buffer
+/// outlives the graph.
+Expected<std::unique_ptr<LinkGraph>>
+createLinkGraphFromELFObject_ppc64le(MemoryBufferRef ObjectBuffer);
+
+/// jit-link the given object buffer, which must be a ELF ppc64le object file.
+///
+/// WARNING: The big-endian backend has not been tested yet.
+void link_ELF_ppc64(std::unique_ptr<LinkGraph> G,
+                    std::unique_ptr<JITLinkContext> Ctx);
+
+/// jit-link the given object buffer, which must be a ELF ppc64le object file.
+void link_ELF_ppc64le(std::unique_ptr<LinkGraph> G,
+                      std::unique_ptr<JITLinkContext> Ctx);
+
+} // end namespace llvm::jitlink
+
+#endif // LLVM_EXECUTIONENGINE_JITLINK_ELF_PPC64_H

llvm/include/llvm/ExecutionEngine/JITLink/ppc64.h

@@ -0,0 +1,44 @@
+//===--- ppc64.h - Generic JITLink ppc64 edge kinds, utilities --*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Generic utilities for graphs representing 64-bit PowerPC objects.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_JITLINK_PPC64_H
+#define LLVM_EXECUTIONENGINE_JITLINK_PPC64_H
+
+#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+
+namespace llvm::jitlink::ppc64 {
+
+/// Represents ppc64 fixups and other ppc64-specific edge kinds.
+/// TODO: Add edge kinds.
+enum EdgeKind_ppc64 : Edge::Kind {};
+
+/// Returns a string name for the given ppc64 edge. For debugging purposes
+/// only.
+const char *getEdgeKindName(Edge::Kind K);
+
+/// Apply fixup expression for edge to block content.
+/// TOOD: Add fixups as we add edges.
+inline Error applyFixup(LinkGraph &G, Block &B, const Edge &E,
+                        const Symbol *GOTSymbol) {
+  switch (E.getKind()) {
+  default:
+    return make_error<JITLinkError>(
+        "In graph " + G.getName() + ", section " + B.getSection().getName() +
+        " unsupported edge kind " + getEdgeKindName(E.getKind()));
+  }
+
+  return Error::success();
+}
+
+} // end namespace llvm::jitlink::ppc64
+
+#endif // LLVM_EXECUTIONENGINE_JITLINK_PPC64_H

llvm/lib/ExecutionEngine/JITLink/CMakeLists.txt

@@ -24,6 +24,7 @@ add_llvm_component_library(LLVMJITLink
   ELF_aarch64.cpp
   ELF_i386.cpp
   ELF_loongarch.cpp
+  ELF_ppc64.cpp
   ELF_riscv.cpp
   ELF_x86_64.cpp
 
@@ -38,6 +39,7 @@ add_llvm_component_library(LLVMJITLink
   aarch64.cpp
   i386.cpp
   loongarch.cpp
+  ppc64.cpp
   riscv.cpp
   x86_64.cpp
 

llvm/lib/ExecutionEngine/JITLink/ELF.cpp

@@ -17,6 +17,7 @@
 #include "llvm/ExecutionEngine/JITLink/ELF_aarch64.h"
 #include "llvm/ExecutionEngine/JITLink/ELF_i386.h"
 #include "llvm/ExecutionEngine/JITLink/ELF_loongarch.h"
+#include "llvm/ExecutionEngine/JITLink/ELF_ppc64.h"
 #include "llvm/ExecutionEngine/JITLink/ELF_riscv.h"
 #include "llvm/ExecutionEngine/JITLink/ELF_x86_64.h"
 #include "llvm/Object/ELF.h"
@@ -63,6 +64,7 @@ createLinkGraphFromELFObject(MemoryBufferRef ObjectBuffer) {
   if (memcmp(Buffer.data(), ELF::ElfMagic, strlen(ELF::ElfMagic)) != 0)
     return make_error<JITLinkError>("ELF magic not valid");
 
+  uint8_t DataEncoding = Buffer.data()[ELF::EI_DATA];
   Expected<uint16_t> TargetMachineArch = readTargetMachineArch(Buffer);
   if (!TargetMachineArch)
     return TargetMachineArch.takeError();
@@ -74,6 +76,12 @@ createLinkGraphFromELFObject(MemoryBufferRef ObjectBuffer) {
     return createLinkGraphFromELFObject_aarch32(ObjectBuffer);
   case ELF::EM_LOONGARCH:
     return createLinkGraphFromELFObject_loongarch(ObjectBuffer);
+  case ELF::EM_PPC64: {
+    if (DataEncoding == ELF::ELFDATA2LSB)
+      return createLinkGraphFromELFObject_ppc64le(ObjectBuffer);
+    else
+      return createLinkGraphFromELFObject_ppc64(ObjectBuffer);
+  }
   case ELF::EM_RISCV:
     return createLinkGraphFromELFObject_riscv(ObjectBuffer);
   case ELF::EM_X86_64:
@@ -103,6 +111,12 @@ void link_ELF(std::unique_ptr<LinkGraph> G,
   case Triple::loongarch64:
     link_ELF_loongarch(std::move(G), std::move(Ctx));
     return;
+  case Triple::ppc64:
+    link_ELF_ppc64(std::move(G), std::move(Ctx));
+    return;
+  case Triple::ppc64le:
+    link_ELF_ppc64le(std::move(G), std::move(Ctx));
+    return;
   case Triple::riscv32:
   case Triple::riscv64:
     link_ELF_riscv(std::move(G), std::move(Ctx));

llvm/lib/ExecutionEngine/JITLink/ELF_ppc64.cpp

@@ -0,0 +1,158 @@
+//===------- ELF_ppc64.cpp -JIT linker implementation for ELF/ppc64 -------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// ELF/ppc64 jit-link implementation.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ExecutionEngine/JITLink/ELF_ppc64.h"
+#include "llvm/ExecutionEngine/JITLink/ppc64.h"
+#include "llvm/Object/ELFObjectFile.h"
+#include "llvm/Support/Endian.h"
+
+#include "ELFLinkGraphBuilder.h"
+#include "JITLinkGeneric.h"
+
+#define DEBUG_TYPE "jitlink"
+
+namespace llvm::jitlink {
+
+template <support::endianness Endianness>
+class ELFLinkGraphBuilder_ppc64
+    : public ELFLinkGraphBuilder<object::ELFType<Endianness, true>> {
+private:
+  using ELFT = object::ELFType<Endianness, true>;
+  using Base = ELFLinkGraphBuilder<ELFT>;
+
+  using Base::G; // Use LinkGraph pointer from base class.
+
+  Error addRelocations() override {
+    LLVM_DEBUG(dbgs() << "Processing relocations:\n");
+
+    using Self = ELFLinkGraphBuilder_ppc64<Endianness>;
+    for (const auto &RelSect : Base::Sections) {
+      // Validate the section to read relocation entries from.
+      if (RelSect.sh_type == ELF::SHT_REL)
+        return make_error<StringError>("No SHT_REL in valid " +
+                                           G->getTargetTriple().getArchName() +
+                                           " ELF object files",
+                                       inconvertibleErrorCode());
+
+      if (Error Err = Base::forEachRelaRelocation(RelSect, this,
+                                                  &Self::addSingleRelocation))
+        return Err;
+    }
+
+    return Error::success();
+  }
+
+  Error addSingleRelocation(const typename ELFT::Rela &Rel,
+                            const typename ELFT::Shdr &FixupSection,
+                            Block &BlockToFix) {
+    auto ELFReloc = Rel.getType(false);
+    return make_error<JITLinkError>(
+        "In " + G->getName() + ": Unsupported ppc64 relocation type " +
+        object::getELFRelocationTypeName(ELF::EM_PPC64, ELFReloc));
+  }
+
+public:
+  ELFLinkGraphBuilder_ppc64(StringRef FileName,
+                            const object::ELFFile<ELFT> &Obj, Triple TT,
+                            LinkGraph::FeatureVector Features)
+      : ELFLinkGraphBuilder<ELFT>(Obj, std::move(TT), std::move(Features),
+                                  FileName, ppc64::getEdgeKindName) {}
+};
+
+template <support::endianness Endianness>
+class ELFJITLinker_ppc64 : public JITLinker<ELFJITLinker_ppc64<Endianness>> {
+  using JITLinkerBase = JITLinker<ELFJITLinker_ppc64<Endianness>>;
+  friend JITLinkerBase;
+
+public:
+  ELFJITLinker_ppc64(std::unique_ptr<JITLinkContext> Ctx,
+                     std::unique_ptr<LinkGraph> G, PassConfiguration PassConfig)
+      : JITLinkerBase(std::move(Ctx), std::move(G), std::move(PassConfig)) {}
+
+private:
+  Symbol *GOTSymbol = nullptr;
+
+  Error applyFixup(LinkGraph &G, Block &B, const Edge &E) const {
+    return ppc64::applyFixup(G, B, E, GOTSymbol);
+  }
+};
+
+template <support::endianness Endianness>
+Expected<std::unique_ptr<LinkGraph>>
+createLinkGraphFromELFObject_ppc64(MemoryBufferRef ObjectBuffer) {
+  LLVM_DEBUG({
+    dbgs() << "Building jitlink graph for new input "
+           << ObjectBuffer.getBufferIdentifier() << "...\n";
+  });
+
+  auto ELFObj = object::ObjectFile::createELFObjectFile(ObjectBuffer);
+  if (!ELFObj)
+    return ELFObj.takeError();
+
+  auto Features = (*ELFObj)->getFeatures();
+  if (!Features)
+    return Features.takeError();
+
+  using ELFT = object::ELFType<Endianness, true>;
+  auto &ELFObjFile = cast<object::ELFObjectFile<ELFT>>(**ELFObj);
+  return ELFLinkGraphBuilder_ppc64<Endianness>(
+             (*ELFObj)->getFileName(), ELFObjFile.getELFFile(),
+             (*ELFObj)->makeTriple(), Features->getFeatures())
+      .buildGraph();
+}
+
+template <support::endianness Endianness>
+void link_ELF_ppc64(std::unique_ptr<LinkGraph> G,
+                    std::unique_ptr<JITLinkContext> Ctx) {
+  PassConfiguration Config;
+
+  if (Ctx->shouldAddDefaultTargetPasses(G->getTargetTriple())) {
+    // Construct a JITLinker and run the link function.
+    // Add a mark-live pass.
+    if (auto MarkLive = Ctx->getMarkLivePass(G->getTargetTriple()))
+      Config.PrePrunePasses.push_back(std::move(MarkLive));
+    else
+      Config.PrePrunePasses.push_back(markAllSymbolsLive);
+  }
+
+  if (auto Err = Ctx->modifyPassConfig(*G, Config))
+    return Ctx->notifyFailed(std::move(Err));
+
+  ELFJITLinker_ppc64<Endianness>::link(std::move(Ctx), std::move(G),
+                                       std::move(Config));
+}
+
+Expected<std::unique_ptr<LinkGraph>>
+createLinkGraphFromELFObject_ppc64(MemoryBufferRef ObjectBuffer) {
+  return createLinkGraphFromELFObject_ppc64<support::big>(
+      std::move(ObjectBuffer));
+}
+
+Expected<std::unique_ptr<LinkGraph>>
+createLinkGraphFromELFObject_ppc64le(MemoryBufferRef ObjectBuffer) {
+  return createLinkGraphFromELFObject_ppc64<support::little>(
+      std::move(ObjectBuffer));
+}
+
+/// jit-link the given object buffer, which must be a ELF ppc64 object file.
+void link_ELF_ppc64(std::unique_ptr<LinkGraph> G,
+                    std::unique_ptr<JITLinkContext> Ctx) {
+  return link_ELF_ppc64<support::big>(std::move(G), std::move(Ctx));
+}
+
+/// jit-link the given object buffer, which must be a ELF ppc64le object file.
+void link_ELF_ppc64le(std::unique_ptr<LinkGraph> G,
+                      std::unique_ptr<JITLinkContext> Ctx) {
+  return link_ELF_ppc64<support::little>(std::move(G), std::move(Ctx));
+}
+
+} // end namespace llvm::jitlink

llvm/lib/ExecutionEngine/JITLink/ppc64.cpp

@@ -0,0 +1,27 @@
+//===----- ppc64.cpp - Generic JITLink ppc64 edge kinds, utilities ------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Generic utilities for graphs representing 64-bit PowerPC objects.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ExecutionEngine/JITLink/ppc64.h"
+
+#define DEBUG_TYPE "jitlink"
+
+namespace llvm::jitlink::ppc64 {
+
+const char *getEdgeKindName(Edge::Kind K) {
+  // TODO: Add edge names.
+  switch (K) {
+  default:
+    return getGenericEdgeKindName(static_cast<Edge::Kind>(K));
+  }
+}
+
+} // end namespace llvm::jitlink::ppc64

llvm/test/ExecutionEngine/JITLink/ppc64/lit.local.cfg

@@ -0,0 +1,2 @@
+if not 'PowerPC' in config.root.targets:
+  config.unsupported = True

llvm/test/ExecutionEngine/JITLink/ppc64/ppc64le-no-relocs.s

@@ -0,0 +1,20 @@
+# RUN: llvm-mc -triple=powerpc64le-unknown-linux-gnu -filetype=obj -o %t %s
+# RUN: llvm-jitlink -noexec %t
+#
+# Check that a program that just returns immediately from main (requiring no
+# relocations at all) loads under llvm-jitlink.
+
+	.text
+	.abiversion 2
+	.file	"ppc64le-no-relocs.c"
+	.globl	main
+	.p2align	4
+	.type	main,@function
+main:
+.Lfunc_begin0:
+	li 3, 0
+	blr
+	.long	0
+	.quad	0
+.Lfunc_end0:
+	.size	main, .Lfunc_end0-.Lfunc_begin0