[lld] [lld] Add target support for SystemZ (s390x) (PR #75643)

[Fangrui Song via llvm-commits]

================
@@ -0,0 +1,587 @@
+//===- SystemZ.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
+//
+//===----------------------------------------------------------------------===//
+
+#include "OutputSections.h"
+#include "Symbols.h"
+#include "SyntheticSections.h"
+#include "Target.h"
+#include "lld/Common/ErrorHandler.h"
+#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/Support/Endian.h"
+
+using namespace llvm;
+using namespace llvm::object;
+using namespace llvm::support::endian;
+using namespace llvm::ELF;
+using namespace lld;
+using namespace lld::elf;
+
+namespace {
+class SystemZ : public TargetInfo {
+public:
+  SystemZ();
+  RelExpr getRelExpr(RelType type, const Symbol &s,
+                     const uint8_t *loc) const override;
+  RelType getDynRel(RelType type) const override;
+  void writeGotHeader(uint8_t *buf) const override;
+  void writeGotPlt(uint8_t *buf, const Symbol &s) const override;
+  void writeIgotPlt(uint8_t *buf, const Symbol &s) const override;
+  void writePltHeader(uint8_t *buf) const override;
+  void addPltHeaderSymbols(InputSection &isd) const override;
+  void writePlt(uint8_t *buf, const Symbol &sym,
+                uint64_t pltEntryAddr) const override;
+  RelExpr adjustTlsExpr(RelType type, RelExpr expr) const override;
+  RelExpr adjustGotPcExpr(RelType type, int64_t addend,
+                          const uint8_t *loc) const override;
+  bool relaxOnce(int pass) const override;
+  void relocate(uint8_t *loc, const Relocation &rel,
+                uint64_t val) const override;
+  int64_t getImplicitAddend(const uint8_t *buf, RelType type) const override;
+
+private:
+  void relaxGot(uint8_t *loc, const Relocation &rel, uint64_t val) const;
+  void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel, uint64_t val) const;
+  void relaxTlsGdToLe(uint8_t *loc, const Relocation &rel, uint64_t val) const;
+  void relaxTlsLdToLe(uint8_t *loc, const Relocation &rel, uint64_t val) const;
+};
+} // namespace
+
+SystemZ::SystemZ() {
+  copyRel = R_390_COPY;
+  gotRel = R_390_GLOB_DAT;
+  pltRel = R_390_JMP_SLOT;
+  relativeRel = R_390_RELATIVE;
+  iRelativeRel = R_390_IRELATIVE;
+  symbolicRel = R_390_64;
+  tlsGotRel = R_390_TLS_TPOFF;
+  tlsModuleIndexRel = R_390_TLS_DTPMOD;
+  tlsOffsetRel = R_390_TLS_DTPOFF;
+  gotHeaderEntriesNum = 3;
+  gotPltHeaderEntriesNum = 0;
+  gotEntrySize = 8;
+  pltHeaderSize = 32;
+  pltEntrySize = 32;
+  ipltEntrySize = 32;
+
+  // This "trap instruction" is used to fill gaps between sections.
+  // On SystemZ, the behavior of the GNU ld is to fill those gaps
+  // with nop instructions instead - and unfortunately the default
+  // glibc crt object files (used to) rely on that behavior since
+  // they use an alignment on the .init section fragments that causes
+  // gaps which must be filled with nops as they are being executed.
+  // Therefore, we provide a nop instruction as "trapInstr" here.
+  trapInstr = {0x07, 0x07, 0x07, 0x07};
+
+  defaultImageBase = 0x1000000;
+}
+
+RelExpr SystemZ::getRelExpr(RelType type, const Symbol &s,
+                            const uint8_t *loc) const {
+  switch (type) {
+  case R_390_NONE:
+    return R_NONE;
+  // Relocations targeting the symbol value.
+  case R_390_8:
+  case R_390_12:
+  case R_390_16:
+  case R_390_20:
+  case R_390_32:
+  case R_390_64:
+    return R_ABS;
+  case R_390_PC16:
+  case R_390_PC32:
+  case R_390_PC64:
+  case R_390_PC12DBL:
+  case R_390_PC16DBL:
+  case R_390_PC24DBL:
+  case R_390_PC32DBL:
+    return R_PC;
+  case R_390_GOTOFF16:
+  case R_390_GOTOFF: // a.k.a. R_390_GOTOFF32
+  case R_390_GOTOFF64:
+    return R_GOTREL;
+  // Relocations targeting the PLT associated with the symbol.
+  case R_390_PLT32:
+  case R_390_PLT64:
+  case R_390_PLT12DBL:
+  case R_390_PLT16DBL:
+  case R_390_PLT24DBL:
+  case R_390_PLT32DBL:
+    return R_PLT_PC;
+  case R_390_PLTOFF16:
+  case R_390_PLTOFF32:
+  case R_390_PLTOFF64:
+    return R_PLT_GOTREL;
+  // Relocations targeting the GOT entry associated with the symbol.
+  case R_390_GOTENT:
+    return R_GOT_PC;
+  case R_390_GOT12:
+  case R_390_GOT16:
+  case R_390_GOT20:
+  case R_390_GOT32:
+  case R_390_GOT64:
+    return R_GOT_OFF;
+  // Relocations targeting the GOTPLT entry associated with the symbol.
+  case R_390_GOTPLTENT:
+    return R_GOTPLT_PC;
+  case R_390_GOTPLT12:
+  case R_390_GOTPLT16:
+  case R_390_GOTPLT20:
+  case R_390_GOTPLT32:
+  case R_390_GOTPLT64:
+    return R_GOTPLT_OFF;
+  // Relocations targeting _GLOBAL_OFFSET_TABLE_.
+  case R_390_GOTPC:
+  case R_390_GOTPCDBL:
+    return R_GOTONLY_PC;
+  // TLS-related relocations.
+  case R_390_TLS_LOAD:
+    return R_NONE;
+  case R_390_TLS_GDCALL:
+    return R_TLSGD_PC;
+  case R_390_TLS_LDCALL:
+    return R_TLSLD_PC;
+  case R_390_TLS_GD32:
+  case R_390_TLS_GD64:
+    return R_TLSGD_GOT;
+  case R_390_TLS_LDM32:
+  case R_390_TLS_LDM64:
+    return R_TLSLD_GOT;
+  case R_390_TLS_LDO32:
+  case R_390_TLS_LDO64:
+    return R_DTPREL;
+  case R_390_TLS_LE32:
+  case R_390_TLS_LE64:
+    return R_TPREL;
+  case R_390_TLS_IE32:
+  case R_390_TLS_IE64:
----------------
MaskRay wrote:

Thanks. IIUC TLS_IE{32,64} are not useful in the presence of TLS_IEENT.

https://github.com/llvm/llvm-project/pull/75643