[lld] Add thunks for hexagon

Co-authored-by: Alexey Karyakin <[email protected]>

Author: androm3da

lld/ELF/Arch/Hexagon.cpp

@@ -10,6 +10,7 @@
 #include "Symbols.h"
 #include "SyntheticSections.h"
 #include "Target.h"
+#include "Thunks.h"
 #include "lld/Common/ErrorHandler.h"
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/Support/Endian.h"
@@ -30,6 +31,10 @@ class Hexagon final : public TargetInfo {
                      const uint8_t *loc) const override;
   RelType getDynRel(RelType type) const override;
   int64_t getImplicitAddend(const uint8_t *buf, RelType type) const override;
+  bool needsThunk(RelExpr expr, RelType type, const InputFile *file,
+                  uint64_t branchAddr, const Symbol &s,
+                  int64_t a) const override;
+  bool inBranchRange(RelType type, uint64_t src, uint64_t dst) const override;
   void relocate(uint8_t *loc, const Relocation &rel,
                 uint64_t val) const override;
   void writePltHeader(uint8_t *buf) const override;
@@ -57,6 +62,8 @@ Hexagon::Hexagon(Ctx &ctx) : TargetInfo(ctx) {
   tlsGotRel = R_HEX_TPREL_32;
   tlsModuleIndexRel = R_HEX_DTPMOD_32;
   tlsOffsetRel = R_HEX_DTPREL_32;
+
+  needsThunks = true;
 }
 
 uint32_t Hexagon::calcEFlags() const {
@@ -252,6 +259,34 @@ static uint32_t findMaskR16(Ctx &ctx, uint32_t insn) {
 
 static void or32le(uint8_t *p, int32_t v) { write32le(p, read32le(p) | v); }
 
+bool Hexagon::inBranchRange(RelType type, uint64_t src, uint64_t dst) const {
+  int64_t offset = dst - src;
+  switch (type) {
+  case llvm::ELF::R_HEX_B22_PCREL:
+  case llvm::ELF::R_HEX_PLT_B22_PCREL:
+  case llvm::ELF::R_HEX_GD_PLT_B22_PCREL:
+  case llvm::ELF::R_HEX_LD_PLT_B22_PCREL:
+    return llvm::isInt<22>(offset >> 2);
+  case llvm::ELF::R_HEX_B15_PCREL:
+    return llvm::isInt<15>(offset >> 2);
+    break;
+  case llvm::ELF::R_HEX_B13_PCREL:
+    return llvm::isInt<13>(offset >> 2);
+    break;
+  case llvm::ELF::R_HEX_B9_PCREL:
+    return llvm::isInt<9>(offset >> 2);
+  default:
+    return true;
+  }
+  llvm_unreachable("unsupported relocation");
+}
+
+bool Hexagon::needsThunk(RelExpr expr, RelType type, const InputFile *file,
+                         uint64_t branchAddr, const Symbol &s,
+                         int64_t a) const {
+  return !ctx.target->inBranchRange(type, branchAddr, s.getVA(ctx, a));
+}
+
 void Hexagon::relocate(uint8_t *loc, const Relocation &rel,
                        uint64_t val) const {
   switch (rel.type) {

lld/ELF/Relocations.cpp

@@ -2031,17 +2031,44 @@ void ThunkCreator::mergeThunks(ArrayRef<OutputSection *> outputSections) {
       });
 }
 
-static int64_t getPCBias(Ctx &ctx, RelType type) {
-  if (ctx.arg.emachine != EM_ARM)
-    return 0;
-  switch (type) {
-  case R_ARM_THM_JUMP19:
-  case R_ARM_THM_JUMP24:
-  case R_ARM_THM_CALL:
-    return 4;
-  default:
-    return 8;
+static const uint32_t HEXAGON_MASK_END_PACKET = 3 << 14;
+static const uint32_t HEXAGON_END_OF_PACKET = 3 << 14;
+static const uint32_t HEXAGON_END_OF_DUPLEX = 0 << 14;
+
+// Return the distance between the packet start and the instruction in the
+// relocation.
+static int getHexagonPacketOffset(const InputSection &isec,
+                                  const Relocation &rel) {
+  const ArrayRef<uint8_t> SectContents = isec.content();
+
+  // Search back as many as 3 instructions.
+  for (unsigned i = 0;; i++) {
+    if (i == 3 || rel.offset < (i + 1) * 4)
+      return i * 4;
+    uint32_t instWord = 0;
+    const ArrayRef<uint8_t> InstWordContents =
+        SectContents.drop_front(rel.offset - (i + 1) * 4);
+    ::memcpy(&instWord, InstWordContents.data(), sizeof(instWord));
+    if (((instWord & HEXAGON_MASK_END_PACKET) == HEXAGON_END_OF_PACKET) ||
+        ((instWord & HEXAGON_MASK_END_PACKET) == HEXAGON_END_OF_DUPLEX))
+      return i * 4;
+  }
+}
+static int64_t getPCBias(Ctx &ctx, const InputSection &isec,
+                         const Relocation &rel) {
+  if (ctx.arg.emachine == EM_ARM) {
+    switch (rel.type) {
+    case R_ARM_THM_JUMP19:
+    case R_ARM_THM_JUMP24:
+    case R_ARM_THM_CALL:
+      return 4;
+    default:
+      return 8;
+    }
   }
+  if (ctx.arg.emachine == EM_HEXAGON)
+    return -getHexagonPacketOffset(isec, rel);
+  return 0;
 }
 
 // Find or create a ThunkSection within the InputSectionDescription (ISD) that
@@ -2053,7 +2080,7 @@ ThunkSection *ThunkCreator::getISDThunkSec(OutputSection *os,
                                            const Relocation &rel,
                                            uint64_t src) {
   // See the comment in getThunk for -pcBias below.
-  const int64_t pcBias = getPCBias(ctx, rel.type);
+  const int64_t pcBias = getPCBias(ctx, *isec, rel);
   for (std::pair<ThunkSection *, uint32_t> tp : isd->thunkSections) {
     ThunkSection *ts = tp.first;
     uint64_t tsBase = os->addr + ts->outSecOff - pcBias;
@@ -2214,7 +2241,7 @@ std::pair<Thunk *, bool> ThunkCreator::getThunk(InputSection *isec,
   // out in the relocation addend. We compensate for the PC bias so that
   // an Arm and Thumb relocation to the same destination get the same keyAddend,
   // which is usually 0.
-  const int64_t pcBias = getPCBias(ctx, rel.type);
+  const int64_t pcBias = getPCBias(ctx, *isec, rel);
   const int64_t keyAddend = rel.addend + pcBias;
 
   // We use a ((section, offset), addend) pair to find the thunk position if
@@ -2373,7 +2400,7 @@ bool ThunkCreator::createThunks(uint32_t pass,
             // STT_SECTION + non-zero addend, clear the addend after
             // redirection.
             if (ctx.arg.emachine != EM_MIPS)
-              rel.addend = -getPCBias(ctx, rel.type);
+              rel.addend = -getPCBias(ctx, *isec, rel);
           }
 
         for (auto &p : isd->thunkSections)

lld/ELF/Thunks.cpp

@@ -402,6 +402,21 @@ class AVRThunk : public Thunk {
   void addSymbols(ThunkSection &isec) override;
 };
 
+// Hexagon CPUs need thunks for <<FIXME TBD>>
+// when their destination is out of range [0, 0x_?].
+class HexagonThunk : public Thunk {
+public:
+  HexagonThunk(Ctx &ctx, const InputSection &isec, Relocation &rel,
+               Symbol &dest)
+      : Thunk(ctx, dest, 0), relOffset(rel.offset) {
+    alignment = 4;
+  }
+  uint32_t relOffset;
+  uint32_t size() override { return ctx.arg.isPic ? 12 : 8; }
+  void writeTo(uint8_t *buf) override;
+  void addSymbols(ThunkSection &isec) override;
+};
+
 // MIPS LA25 thunk
 class MipsThunk final : public Thunk {
 public:
@@ -1468,6 +1483,39 @@ bool PPC64LongBranchThunk::isCompatibleWith(const InputSection &isec,
   return rel.type == R_PPC64_REL24 || rel.type == R_PPC64_REL14;
 }
 
+// Hexagon Target Thunks
+static uint64_t getHexagonThunkDestVA(Ctx &ctx, const Symbol &s, int64_t a) {
+  uint64_t v = s.isInPlt(ctx) ? s.getPltVA(ctx) : s.getVA(ctx, a);
+  return SignExtend64<32>(v); // FIXME: sign extend to 64-bit?
+}
+
+void HexagonThunk::writeTo(uint8_t *buf) {
+  uint64_t s = getHexagonThunkDestVA(ctx, destination, addend);
+  uint64_t p = getThunkTargetSym()->getVA(ctx);
+
+  if (ctx.arg.isPic) {
+    write32(ctx, buf + 0, 0x00004000); // {  immext(#0)
+    ctx.target->relocateNoSym(buf, R_HEX_B32_PCREL_X, s - p);
+    write32(ctx, buf + 4, 0x6a49c00e); //    r14 = add(pc,##0) }
+    ctx.target->relocateNoSym(buf + 4, R_HEX_6_PCREL_X, s - p);
+
+    write32(ctx, buf + 8, 0x528ec000); // {  jumpr r14 }
+  } else {
+    write32(ctx, buf + 0, 0x00004000); //  { immext
+    ctx.target->relocateNoSym(buf, R_HEX_B32_PCREL_X, s - p);
+    write32(ctx, buf + 4, 0x5800c000); //    jump <> }
+    ctx.target->relocateNoSym(buf + 4, R_HEX_B22_PCREL_X, s - p);
+  }
+}
+void HexagonThunk::addSymbols(ThunkSection &isec) {
+  Symbol *enclosing = isec.getEnclosingSymbol(relOffset);
+  StringRef src = enclosing ? enclosing->getName() : isec.name;
+
+  addSymbol(saver().save("__trampoline_for_" + destination.getName() +
+                         "_from_" + src),
+            STT_FUNC, 0, isec);
+}
+
 Thunk::Thunk(Ctx &ctx, Symbol &d, int64_t a)
     : ctx(ctx), destination(d), addend(a), offset(0) {
   destination.thunkAccessed = true;
@@ -1637,6 +1685,24 @@ static std::unique_ptr<Thunk> addThunkAVR(Ctx &ctx, RelType type, Symbol &s,
   }
 }
 
+static std::unique_ptr<Thunk> addThunkHexagon(Ctx &ctx,
+                                              const InputSection &isec,
+                                              Relocation &rel, Symbol &s) {
+  switch (rel.type) {
+  case R_HEX_B9_PCREL:
+  case R_HEX_B13_PCREL:
+  case R_HEX_B15_PCREL:
+  case R_HEX_B22_PCREL:
+  case R_HEX_PLT_B22_PCREL:
+  case R_HEX_GD_PLT_B22_PCREL:
+    return std::make_unique<HexagonThunk>(ctx, isec, rel, s);
+  default:
+    Fatal(ctx) << "unrecognized relocation " << rel.type << " to " << &s
+               << " for hexagon target";
+    llvm_unreachable("");
+  }
+}
+
 static std::unique_ptr<Thunk> addThunkMips(Ctx &ctx, RelType type, Symbol &s) {
   if ((s.stOther & STO_MIPS_MICROMIPS) && isMipsR6(ctx))
     return std::make_unique<MicroMipsR6Thunk>(ctx, s);
@@ -1706,8 +1772,11 @@ std::unique_ptr<Thunk> elf::addThunk(Ctx &ctx, const InputSection &isec,
     return addThunkPPC32(ctx, isec, rel, s);
   case EM_PPC64:
     return addThunkPPC64(ctx, rel.type, s, a);
+  case EM_HEXAGON:
+    return addThunkHexagon(ctx, isec, rel, s);
   default:
-    llvm_unreachable("add Thunk only supported for ARM, AVR, Mips and PowerPC");
+    llvm_unreachable(
+        "add Thunk only supported for ARM, AVR, Hexagon, Mips and PowerPC");
   }
 }
 

lld/test/ELF/hexagon-jump-error.s

@@ -0,0 +1,119 @@
+# REQUIRES: hexagon
+# RUN: llvm-mc -filetype=obj -triple=hexagon-unknown-linux-musl %s -o %t.o
+# RUN: ld.lld %t.o -o %t
+# RUN: llvm-objdump -d %t 2>&1 | FileCheck --check-prefix=CHECK-NONPIC %s
+# RUN: llvm-mc -filetype=obj --position-independent \
+# RUN:         -triple=hexagon-unknown-linux-musl %s -o %t.o
+# RUN: ld.lld --pie %t.o -o %t
+# RUN: llvm-objdump -d %t 2>&1 | FileCheck --check-prefix=CHECK-PIC %s
+
+# Packets with pc-relative relocations are more interesting because
+# the offset must be relative to the start of the source, destination
+# packets and not necessarily the instruction word containing the jump/call.
+
+# CHECK:  Disassembly of section .text:
+
+# CHECK-NONPIC: 000200b4 <__trampoline_for_myfn_a_from_.text.thunk>:
+# CHECK-NONPIC: { immext(#0x1000040)
+# CHECK-NONPIC:   jump 0x1020110 }
+
+# CHECK-PIC:    00010150 <__trampoline_for_myfn_a_from_.text.thunk>:
+# CHECK-PIC:    { immext(#0x1000040)
+# CHECK-PIC:      r14 = add(pc,##0x1000060) }
+# CHECK-PIC:    { jumpr r14 }
+
+# CHECK-NONPIC: 000200bc <myfn_b>:
+# CHECK-NONPIC: { jumpr r31 }
+# CHECK-PIC:    0001015c <myfn_b>:
+# CHECK-PIC:    { jumpr r31 }
+    .globl myfn_b
+    .type  myfn_b, @function
+myfn_b:
+    jumpr r31
+    .size  myfn_b, .-myfn_b
+
+# CHECK-PIC:    00010160 <main>:
+    .globl main
+    .type  main, @function
+main:
+    { r0 = #0
+      call myfn_a }
+# CHECK-PIC:      { call 0x10150
+# CHECK-NONPIC:   { call 0x200b4
+# CHECK:            r0 = #0x0 }
+    call myfn_a
+# CHECK-PIC:    call 0x10150
+# CHECK-NONPIC: call 0x200b4
+    call myfn_b
+# CHECK-PIC:    call 0x1015c
+# CHECK-NONPIC: call 0x200bc
+
+    { r2 = add(r0, r1)
+      if (p0) call #myfn_b
+      if (!p0) call #myfn_a }
+# CHECK-PIC:     { if (p0) call 0x1015c
+# CHECK-PIC:       if (!p0) call 0x10150
+# CHECK-NONPIC:  { if (p0) call 0x200bc
+# CHECK-NONPIC:    if (!p0) call 0x200b4
+# CHECK:           r2 = add(r0,r1) }
+
+    { r2 = add(r0, r1)
+      if (p0) call #myfn_a
+      if (!p0) call #myfn_a }
+# CHECK-PIC:  { if (p0) call 0x10150
+# CHECK-PIC:    if (!p0) call 0x10150
+# CHECK-NONPIC:  { if (p0) call 0x200b4
+# CHECK-NONPIC:    if (!p0) call 0x200b4
+# CHECK:           r2 = add(r0,r1) }
+
+    { r2 = add(r0, r1)
+      r1 = r4
+      r4 = r5
+      if (r0 == #0) jump:t #myfn_a }
+# CHECK-PIC:     { if (r0==#0) jump:t 0x10150
+# CHECK-NONPIC:  { if (r0==#0) jump:t 0x200b4
+# CHECK:           r2 = add(r0,r1)
+# CHECK:           r1 = r4; r4 = r5 }
+
+    { r2 = add(r0, r1)
+      r4 = r5
+      if (r0 <= #0) jump:t #myfn_a
+      p1 = cmp.eq(r0, #0); if (p1.new) jump:nt #myfn_a }
+# CHECK-NONPIC:  { if (r0<=#0) jump:t 0x200b4
+# CHECK-NONPIC:    p1 = cmp.eq(r0,#0x0); if (p1.new) jump:nt 0x200b4
+# CHECK-PIC:     { if (r0<=#0) jump:t 0x10150
+# CHECK-PIC:       p1 = cmp.eq(r0,#0x0); if (p1.new) jump:nt 0x10150
+# CHECK:           r2 = add(r0,r1)
+# CHECK:           r4 = r5 }
+
+    {r0 = #0; jump #myfn_a}
+# CHECK-PIC:    { r0 = #0x0 ; jump 0x10150 }
+# CHECK-NONPIC: { r0 = #0x0 ; jump 0x200b4 }
+    {r0 = #0; jump #myfn_b}
+# CHECK-PIC:    { r0 = #0x0 ; jump 0x1015c }
+# CHECK-NONPIC: { r0 = #0x0 ; jump 0x200bc }
+    jumpr r31
+    .size   main, .-main
+
+    .section .text.foo
+    .skip 0x1000000
+
+    .globl myfn_a
+    .type  myfn_a, @function
+myfn_a:
+    {r0 = #0; jump #myfn_b}
+    jumpr r31
+    .size  myfn_a, .-myfn_a
+
+# CHECK-NONPIC: 01020110 <myfn_a>:
+# CHECK-NONPIC: { r0 = #0x0 ; jump 0x1020118 }
+# CHECK-NONPIC: { jumpr r31 }
+
+# CHECK-NONPIC: 01020118 <__trampoline_for_myfn_b_from_.text.thunk>:
+# CHECK-NONPIC: { immext(#0xfeffff80)
+# CHECK-NONPIC:   jump 0x200bc }
+
+# CHECK-PIC:    010101b8 <__trampoline_for_myfn_b_from_.text.thunk>:
+# CHECK-PIC:    { immext(#0xfeffff80)
+# CHECK-PIC:      r14 = add(pc,##0xfeffffa4) }
+# CHECK-PIC:    { jumpr r14 }