lld18/0004-Backport-lld-ELF-Support-relax-R_LARCH_ALIGN.patch

From 80c56e85d742bb88533e4789c76ae2b55dc36835 Mon Sep 17 00:00:00 2001
From: Jinyang He <hejinyang@loongson.cn>
Date: Tue, 6 Feb 2024 09:09:13 +0800
Subject: [PATCH 10/14] [lld][ELF] Support relax R_LARCH_ALIGN (#78692)

Refer to commit 6611d58f5bbc ("Relax R_RISCV_ALIGN"), we can relax
R_LARCH_ALIGN by same way. Reuse `SymbolAnchor`, `RISCVRelaxAux` and
`initSymbolAnchors` to simplify codes. As `riscvFinalizeRelax` is an
arch-specific function, put it override on `TargetInfo::finalizeRelax`,
so that LoongArch can override it, too.

The flow of relax R_LARCH_ALIGN is almost consistent with RISCV. The
difference is that LoongArch only has 4-bytes NOP and all executable
insn is 4-bytes aligned. So LoongArch not need rewrite NOP sequence.
Alignment maxBytesEmit parameter is supported in psABI v2.30.

(cherry picked from commit 06a728f3feab876f9195738b5774e82dadc0f3a7)
(cherry picked from commit 60a8ec3a35c722a9eb8298c215321b89d0faf5b5)
Change-Id: I680e9a44f05fb2cc820736eee63ddd999e689daf
---
 lld/ELF/Arch/LoongArch.cpp                 | 156 ++++++++++++++++++++-
 lld/ELF/Arch/RISCV.cpp                     |  28 +---
 lld/ELF/InputSection.cpp                   |   5 +-
 lld/ELF/InputSection.h                     |  24 +++-
 lld/ELF/Target.h                           |   3 +
 lld/ELF/Writer.cpp                         |   4 +-
 lld/test/ELF/loongarch-relax-align.s       | 126 +++++++++++++++++
 lld/test/ELF/loongarch-relax-emit-relocs.s |  49 +++++++
 8 files changed, 362 insertions(+), 33 deletions(-)
 create mode 100644 lld/test/ELF/loongarch-relax-align.s
 create mode 100644 lld/test/ELF/loongarch-relax-emit-relocs.s

diff --git a/lld/ELF/Arch/LoongArch.cpp b/lld/ELF/Arch/LoongArch.cpp
index d3a538577a59..3f57a76873f9 100644
--- a/lld/ELF/Arch/LoongArch.cpp
+++ b/lld/ELF/Arch/LoongArch.cpp
@@ -36,6 +36,8 @@ public:
   bool usesOnlyLowPageBits(RelType type) const override;
   void relocate(uint8_t *loc, const Relocation &rel,
                 uint64_t val) const override;
+  bool relaxOnce(int pass) const override;
+  void finalizeRelax(int passes) const override;
 };
 } // end anonymous namespace
 
@@ -521,8 +523,9 @@ RelExpr LoongArch::getRelExpr(const RelType type, const Symbol &s,
   case R_LARCH_TLS_GD_HI20:
     return R_TLSGD_GOT;
   case R_LARCH_RELAX:
-    // LoongArch linker relaxation is not implemented yet.
-    return R_NONE;
+    return config->relax ? R_RELAX_HINT : R_NONE;
+  case R_LARCH_ALIGN:
+    return R_RELAX_HINT;
 
   // Other known relocs that are explicitly unimplemented:
   //
@@ -696,6 +699,155 @@ void LoongArch::relocate(uint8_t *loc, const Relocation &rel,
   }
 }
 
+static bool relax(InputSection &sec) {
+  const uint64_t secAddr = sec.getVA();
+  const MutableArrayRef<Relocation> relocs = sec.relocs();
+  auto &aux = *sec.relaxAux;
+  bool changed = false;
+  ArrayRef<SymbolAnchor> sa = ArrayRef(aux.anchors);
+  uint64_t delta = 0;
+
+  std::fill_n(aux.relocTypes.get(), relocs.size(), R_LARCH_NONE);
+  aux.writes.clear();
+  for (auto [i, r] : llvm::enumerate(relocs)) {
+    const uint64_t loc = secAddr + r.offset - delta;
+    uint32_t &cur = aux.relocDeltas[i], remove = 0;
+    switch (r.type) {
+    case R_LARCH_ALIGN: {
+      const uint64_t addend =
+          r.sym->isUndefined() ? Log2_64(r.addend) + 1 : r.addend;
+      const uint64_t allBytes = (1 << (addend & 0xff)) - 4;
+      const uint64_t align = 1 << (addend & 0xff);
+      const uint64_t maxBytes = addend >> 8;
+      const uint64_t off = loc & (align - 1);
+      const uint64_t curBytes = off == 0 ? 0 : align - off;
+      // All bytes beyond the alignment boundary should be removed.
+      // If emit bytes more than max bytes to emit, remove all.
+      if (maxBytes != 0 && curBytes > maxBytes)
+        remove = allBytes;
+      else
+        remove = allBytes - curBytes;
+      // If we can't satisfy this alignment, we've found a bad input.
+      if (LLVM_UNLIKELY(static_cast<int32_t>(remove) < 0)) {
+        errorOrWarn(getErrorLocation((const uint8_t *)loc) +
+                    "insufficient padding bytes for " + lld::toString(r.type) +
+                    ": " + Twine(allBytes) + " bytes available for " +
+                    "requested alignment of " + Twine(align) + " bytes");
+        remove = 0;
+      }
+      break;
+    }
+    }
+
+    // For all anchors whose offsets are <= r.offset, they are preceded by
+    // the previous relocation whose `relocDeltas` value equals `delta`.
+    // Decrease their st_value and update their st_size.
+    for (; sa.size() && sa[0].offset <= r.offset; sa = sa.slice(1)) {
+      if (sa[0].end)
+        sa[0].d->size = sa[0].offset - delta - sa[0].d->value;
+      else
+        sa[0].d->value = sa[0].offset - delta;
+    }
+    delta += remove;
+    if (delta != cur) {
+      cur = delta;
+      changed = true;
+    }
+  }
+
+  for (const SymbolAnchor &a : sa) {
+    if (a.end)
+      a.d->size = a.offset - delta - a.d->value;
+    else
+      a.d->value = a.offset - delta;
+  }
+  // Inform assignAddresses that the size has changed.
+  if (!isUInt<32>(delta))
+    fatal("section size decrease is too large: " + Twine(delta));
+  sec.bytesDropped = delta;
+  return changed;
+}
+
+// When relaxing just R_LARCH_ALIGN, relocDeltas is usually changed only once in
+// the absence of a linker script. For call and load/store R_LARCH_RELAX, code
+// shrinkage may reduce displacement and make more relocations eligible for
+// relaxation. Code shrinkage may increase displacement to a call/load/store
+// target at a higher fixed address, invalidating an earlier relaxation. Any
+// change in section sizes can have cascading effect and require another
+// relaxation pass.
+bool LoongArch::relaxOnce(int pass) const {
+  if (config->relocatable)
+    return false;
+
+  if (pass == 0)
+    initSymbolAnchors();
+
+  SmallVector<InputSection *, 0> storage;
+  bool changed = false;
+  for (OutputSection *osec : outputSections) {
+    if (!(osec->flags & SHF_EXECINSTR))
+      continue;
+    for (InputSection *sec : getInputSections(*osec, storage))
+      changed |= relax(*sec);
+  }
+  return changed;
+}
+
+void LoongArch::finalizeRelax(int passes) const {
+  log("relaxation passes: " + Twine(passes));
+  SmallVector<InputSection *, 0> storage;
+  for (OutputSection *osec : outputSections) {
+    if (!(osec->flags & SHF_EXECINSTR))
+      continue;
+    for (InputSection *sec : getInputSections(*osec, storage)) {
+      RelaxAux &aux = *sec->relaxAux;
+      if (!aux.relocDeltas)
+        continue;
+
+      MutableArrayRef<Relocation> rels = sec->relocs();
+      ArrayRef<uint8_t> old = sec->content();
+      size_t newSize = old.size() - aux.relocDeltas[rels.size() - 1];
+      uint8_t *p = context().bAlloc.Allocate<uint8_t>(newSize);
+      uint64_t offset = 0;
+      int64_t delta = 0;
+      sec->content_ = p;
+      sec->size = newSize;
+      sec->bytesDropped = 0;
+
+      // Update section content: remove NOPs for R_LARCH_ALIGN and rewrite
+      // instructions for relaxed relocations.
+      for (size_t i = 0, e = rels.size(); i != e; ++i) {
+        uint32_t remove = aux.relocDeltas[i] - delta;
+        delta = aux.relocDeltas[i];
+        if (remove == 0 && aux.relocTypes[i] == R_LARCH_NONE)
+          continue;
+
+        // Copy from last location to the current relocated location.
+        const Relocation &r = rels[i];
+        uint64_t size = r.offset - offset;
+        memcpy(p, old.data() + offset, size);
+        p += size;
+        offset = r.offset + remove;
+      }
+      memcpy(p, old.data() + offset, old.size() - offset);
+
+      // Subtract the previous relocDeltas value from the relocation offset.
+      // For a pair of R_LARCH_XXX/R_LARCH_RELAX with the same offset, decrease
+      // their r_offset by the same delta.
+      delta = 0;
+      for (size_t i = 0, e = rels.size(); i != e;) {
+        uint64_t cur = rels[i].offset;
+        do {
+          rels[i].offset -= delta;
+          if (aux.relocTypes[i] != R_LARCH_NONE)
+            rels[i].type = aux.relocTypes[i];
+        } while (++i != e && rels[i].offset == cur);
+        delta = aux.relocDeltas[i - 1];
+      }
+    }
+  }
+}
+
 TargetInfo *elf::getLoongArchTargetInfo() {
   static LoongArch target;
   return &target;
diff --git a/lld/ELF/Arch/RISCV.cpp b/lld/ELF/Arch/RISCV.cpp
index d0d75118e30d..06120cabc132 100644
--- a/lld/ELF/Arch/RISCV.cpp
+++ b/lld/ELF/Arch/RISCV.cpp
@@ -44,6 +44,7 @@ public:
   void relocate(uint8_t *loc, const Relocation &rel,
                 uint64_t val) const override;
   bool relaxOnce(int pass) const override;
+  void finalizeRelax(int passes) const override;
 };
 
 } // end anonymous namespace
@@ -513,33 +514,14 @@ void RISCV::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
   }
 }
 
-namespace {
-struct SymbolAnchor {
-  uint64_t offset;
-  Defined *d;
-  bool end; // true for the anchor of st_value+st_size
-};
-} // namespace
-
-struct elf::RISCVRelaxAux {
-  // This records symbol start and end offsets which will be adjusted according
-  // to the nearest relocDeltas element.
-  SmallVector<SymbolAnchor, 0> anchors;
-  // For relocations[i], the actual offset is r_offset - (i ? relocDeltas[i-1] :
-  // 0).
-  std::unique_ptr<uint32_t[]> relocDeltas;
-  // For relocations[i], the actual type is relocTypes[i].
-  std::unique_ptr<RelType[]> relocTypes;
-  SmallVector<uint32_t, 0> writes;
-};
 
-static void initSymbolAnchors() {
+void elf::initSymbolAnchors() {
   SmallVector<InputSection *, 0> storage;
   for (OutputSection *osec : outputSections) {
     if (!(osec->flags & SHF_EXECINSTR))
       continue;
     for (InputSection *sec : getInputSections(*osec, storage)) {
-      sec->relaxAux = make<RISCVRelaxAux>();
+      sec->relaxAux = make<RelaxAux>();
       if (sec->relocs().size()) {
         sec->relaxAux->relocDeltas =
             std::make_unique<uint32_t[]>(sec->relocs().size());
@@ -766,7 +748,7 @@ bool RISCV::relaxOnce(int pass) const {
   return changed;
 }
 
-void elf::riscvFinalizeRelax(int passes) {
+void RISCV::finalizeRelax(int passes) const {
   llvm::TimeTraceScope timeScope("Finalize RISC-V relaxation");
   log("relaxation passes: " + Twine(passes));
   SmallVector<InputSection *, 0> storage;
@@ -774,7 +756,7 @@ void elf::riscvFinalizeRelax(int passes) {
     if (!(osec->flags & SHF_EXECINSTR))
       continue;
     for (InputSection *sec : getInputSections(*osec, storage)) {
-      RISCVRelaxAux &aux = *sec->relaxAux;
+      RelaxAux &aux = *sec->relaxAux;
       if (!aux.relocDeltas)
         continue;
 
diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index 1aff6b968d86..b178d82407e3 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -351,8 +351,9 @@ InputSectionBase *InputSection::getRelocatedSection() const {
 
 template <class ELFT, class RelTy>
 void InputSection::copyRelocations(uint8_t *buf) {
-  if (config->relax && !config->relocatable && config->emachine == EM_RISCV) {
-    // On RISC-V, relaxation might change relocations: copy from
+  if (config->relax && !config->relocatable &&
+      (config->emachine == EM_RISCV || config->emachine == EM_LOONGARCH)) {
+    // On LoongArch and RISC-V, relaxation might change relocations: copy from
     // internal ones that are updated by relaxation.
     InputSectionBase *sec = getRelocatedSection();
     copyRelocations<ELFT, RelTy>(buf, llvm::make_range(sec->relocations.begin(),
diff --git a/lld/ELF/InputSection.h b/lld/ELF/InputSection.h
index 2b91711abba3..842bc369909d 100644
--- a/lld/ELF/InputSection.h
+++ b/lld/ELF/InputSection.h
@@ -101,7 +101,23 @@ protected:
         link(link), info(info) {}
 };
 
-struct RISCVRelaxAux;
+struct SymbolAnchor {
+  uint64_t offset;
+  Defined *d;
+  bool end; // true for the anchor of st_value+st_size
+};
+
+struct RelaxAux {
+  // This records symbol start and end offsets which will be adjusted according
+  // to the nearest relocDeltas element.
+  SmallVector<SymbolAnchor, 0> anchors;
+  // For relocations[i], the actual offset is
+  //   r_offset - (i ? relocDeltas[i-1] : 0).
+  std::unique_ptr<uint32_t[]> relocDeltas;
+  // For relocations[i], the actual type is relocTypes[i].
+  std::unique_ptr<RelType[]> relocTypes;
+  SmallVector<uint32_t, 0> writes;
+};
 
 // This corresponds to a section of an input file.
 class InputSectionBase : public SectionBase {
@@ -222,9 +238,9 @@ public:
     // basic blocks.
     JumpInstrMod *jumpInstrMod = nullptr;
 
-    // Auxiliary information for RISC-V linker relaxation. RISC-V does not use
-    // jumpInstrMod.
-    RISCVRelaxAux *relaxAux;
+    // Auxiliary information for RISC-V and LoongArch linker relaxation.
+    // They do not use jumpInstrMod.
+    RelaxAux *relaxAux;
 
     // The compressed content size when `compressed` is true.
     size_t compressedSize;
diff --git a/lld/ELF/Target.h b/lld/ELF/Target.h
index 47dbe6b4d1c6..bf831afa1793 100644
--- a/lld/ELF/Target.h
+++ b/lld/ELF/Target.h
@@ -94,6 +94,8 @@ public:
 
   // Do a linker relaxation pass and return true if we changed something.
   virtual bool relaxOnce(int pass) const { return false; }
+  // Do finalize relaxation after collecting relaxation infos.
+  virtual void finalizeRelax(int passes) const {}
 
   virtual void applyJumpInstrMod(uint8_t *loc, JumpModType type,
                                  JumpModType val) const {}
@@ -234,6 +236,7 @@ void addArmInputSectionMappingSymbols();
 void addArmSyntheticSectionMappingSymbol(Defined *);
 void sortArmMappingSymbols();
 void convertArmInstructionstoBE8(InputSection *sec, uint8_t *buf);
+void initSymbolAnchors();
 
 LLVM_LIBRARY_VISIBILITY extern const TargetInfo *target;
 TargetInfo *getTarget();
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 368c9aabceae..dd37bbbf76c1 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -1668,8 +1668,8 @@ template <class ELFT> void Writer<ELFT>::finalizeAddressDependentContent() {
       }
     }
   }
-  if (!config->relocatable && config->emachine == EM_RISCV)
-    riscvFinalizeRelax(pass);
+  if (!config->relocatable)
+    target->finalizeRelax(pass);
 
   if (config->relocatable)
     for (OutputSection *sec : outputSections)
diff --git a/lld/test/ELF/loongarch-relax-align.s b/lld/test/ELF/loongarch-relax-align.s
new file mode 100644
index 000000000000..ab61e15d5cac
--- /dev/null
+++ b/lld/test/ELF/loongarch-relax-align.s
@@ -0,0 +1,126 @@
+# REQUIRES: loongarch
+
+# RUN: llvm-mc --filetype=obj --triple=loongarch32 --mattr=+relax %s -o %t.32.o
+# RUN: llvm-mc --filetype=obj --triple=loongarch64 --mattr=+relax %s -o %t.64.o
+# RUN: ld.lld --section-start=.text=0x10000 --section-start=.text2=0x20000 -e 0 %t.32.o -o %t.32
+# RUN: ld.lld --section-start=.text=0x10000 --section-start=.text2=0x20000 -e 0 %t.64.o -o %t.64
+# RUN: ld.lld --section-start=.text=0x10000 --section-start=.text2=0x20000 -e 0 %t.32.o --no-relax -o %t.32n
+# RUN: ld.lld --section-start=.text=0x10000 --section-start=.text2=0x20000 -e 0 %t.64.o --no-relax -o %t.64n
+# RUN: llvm-objdump -td --no-show-raw-insn %t.32 | FileCheck %s
+# RUN: llvm-objdump -td --no-show-raw-insn %t.64 | FileCheck %s
+# RUN: llvm-objdump -td --no-show-raw-insn %t.32n | FileCheck %s
+# RUN: llvm-objdump -td --no-show-raw-insn %t.64n | FileCheck %s
+
+## Test the R_LARCH_ALIGN without symbol index.
+# RUN: llvm-mc --filetype=obj --triple=loongarch64 --mattr=+relax %s -o %t.o64.o --defsym=old=1
+# RUN: ld.lld --section-start=.text=0x10000 --section-start=.text2=0x20000 -e 0 %t.o64.o -o %t.o64
+# RUN: ld.lld --section-start=.text=0x10000 --section-start=.text2=0x20000 -e 0 %t.o64.o --no-relax -o %t.o64n
+# RUN: llvm-objdump -td --no-show-raw-insn %t.o64 | FileCheck %s
+# RUN: llvm-objdump -td --no-show-raw-insn %t.o64n | FileCheck %s
+
+## -r keeps section contents unchanged.
+# RUN: ld.lld -r %t.64.o -o %t.64.r
+# RUN: llvm-objdump -dr --no-show-raw-insn %t.64.r | FileCheck %s --check-prefix=CHECKR
+
+# CHECK-DAG: {{0*}}10000 l .text  {{0*}}44 .Ltext_start
+# CHECK-DAG: {{0*}}10038 l .text  {{0*}}0c .L1
+# CHECK-DAG: {{0*}}10040 l .text  {{0*}}04 .L2
+# CHECK-DAG: {{0*}}20000 l .text2 {{0*}}14 .Ltext2_start
+
+# CHECK:      <.Ltext_start>:
+# CHECK-NEXT:   break 1
+# CHECK-NEXT:   break 2
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   break 3
+# CHECK-NEXT:   break 4
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   pcalau12i     $a0, 0
+# CHECK-NEXT:   addi.{{[dw]}} $a0, $a0, 0
+# CHECK-NEXT:   pcalau12i     $a0, 0
+# CHECK-NEXT:   addi.{{[dw]}} $a0, $a0, 56
+# CHECK-NEXT:   pcalau12i     $a0, 0
+# CHECK-NEXT:   addi.{{[dw]}} $a0, $a0, 64
+# CHECK-EMPTY:
+# CHECK-NEXT: <.L1>:
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   nop
+# CHECK-EMPTY:
+# CHECK-NEXT: <.L2>:
+# CHECK-NEXT:   break 5
+
+# CHECK:      <.Ltext2_start>:
+# CHECK-NEXT:   pcalau12i     $a0, 0
+# CHECK-NEXT:   addi.{{[dw]}} $a0, $a0, 0
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   break 6
+
+# CHECKR:      <.Ltext2_start>:
+# CHECKR-NEXT:   pcalau12i $a0, 0
+# CHECKR-NEXT:   {{0*}}00: R_LARCH_PCALA_HI20 .Ltext2_start
+# CHECKR-NEXT:   {{0*}}00: R_LARCH_RELAX      *ABS*
+# CHECKR-NEXT:   addi.d    $a0, $a0, 0
+# CHECKR-NEXT:   {{0*}}04: R_LARCH_PCALA_LO12 .Ltext2_start
+# CHECKR-NEXT:   {{0*}}04: R_LARCH_RELAX      *ABS*
+# CHECKR-NEXT:   nop
+# CHECKR-NEXT:   {{0*}}08: R_LARCH_ALIGN      .Lalign_symbol+0x4
+# CHECKR-NEXT:   nop
+# CHECKR-NEXT:   nop
+# CHECKR-NEXT:   break 6
+
+.macro .fake_p2align_4 max=0
+  .ifdef old
+    .if \max==0
+      .reloc ., R_LARCH_ALIGN, 0xc
+      nop; nop; nop
+    .endif
+  .else
+    .reloc ., R_LARCH_ALIGN, .Lalign_symbol + 0x4 + (\max << 8)
+    nop; nop; nop
+  .endif
+.endm
+
+  .text
+.Lalign_symbol:
+.Ltext_start:
+  break 1
+  break 2
+## +0x8: Emit 2 nops, delete 1 nop.
+  .fake_p2align_4
+
+  break 3
+## +0x14: Emit 3 nops > 8 bytes, not emit.
+  .fake_p2align_4 8
+
+  break 4
+  .fake_p2align_4 8
+## +0x18: Emit 2 nops <= 8 bytes.
+
+## Compensate
+.ifdef old
+  nop; nop
+.endif
+
+## +0x20: Test symbol value and symbol size can be handled.
+  la.pcrel $a0, .Ltext_start
+  la.pcrel $a0, .L1
+  la.pcrel $a0, .L2
+
+## +0x38: Emit 2 nops, delete 1 nop.
+.L1:
+  .fake_p2align_4
+.L2:
+  break 5
+  .size .L1, . - .L1
+  .size .L2, . - .L2
+  .size .Ltext_start, . - .Ltext_start
+
+## Test another text section.
+  .section .text2,"ax",@progbits
+.Ltext2_start:
+  la.pcrel $a0, .Ltext2_start
+  .fake_p2align_4
+  break 6
+  .size .Ltext2_start, . - .Ltext2_start
diff --git a/lld/test/ELF/loongarch-relax-emit-relocs.s b/lld/test/ELF/loongarch-relax-emit-relocs.s
new file mode 100644
index 000000000000..581fce8c95ca
--- /dev/null
+++ b/lld/test/ELF/loongarch-relax-emit-relocs.s
@@ -0,0 +1,49 @@
+# REQUIRES: loongarch
+## Test that we can handle --emit-relocs while relaxing.
+
+# RUN: llvm-mc --filetype=obj --triple=loongarch32 --mattr=+relax %s -o %t.32.o
+# RUN: llvm-mc --filetype=obj --triple=loongarch64 --mattr=+relax %s -o %t.64.o
+# RUN: ld.lld -Ttext=0x10000 --emit-relocs %t.32.o -o %t.32
+# RUN: ld.lld -Ttext=0x10000 --emit-relocs %t.64.o -o %t.64
+# RUN: llvm-objdump -dr %t.32 | FileCheck %s
+# RUN: llvm-objdump -dr %t.64 | FileCheck %s
+
+## -r should keep original relocations.
+# RUN: ld.lld -r %t.64.o -o %t.64.r
+# RUN: llvm-objdump -dr %t.64.r | FileCheck %s --check-prefix=CHECKR
+
+## --no-relax should keep original relocations.
+## TODO Due to R_LARCH_RELAX is not relaxed, it plays same as --relax now.
+# RUN: ld.lld -Ttext=0x10000 --emit-relocs --no-relax %t.64.o -o %t.64.norelax
+# RUN: llvm-objdump -dr %t.64.norelax | FileCheck %s
+
+# CHECK:      00010000 <_start>:
+# CHECK-NEXT:   pcalau12i $a0, 0
+# CHECK-NEXT:     R_LARCH_PCALA_HI20 _start
+# CHECK-NEXT:     R_LARCH_RELAX *ABS*
+# CHECK-NEXT:   addi.{{[dw]}} $a0, $a0, 0
+# CHECK-NEXT:     R_LARCH_PCALA_LO12 _start
+# CHECK-NEXT:     R_LARCH_RELAX *ABS*
+# CHECK-NEXT:   nop
+# CHECK-NEXT:     R_LARCH_ALIGN .Lla-relax-align0+0x4
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   ret
+
+# CHECKR:      <_start>:
+# CHECKR-NEXT:   pcalau12i $a0, 0
+# CHECKR-NEXT:     R_LARCH_PCALA_HI20 _start
+# CHECKR-NEXT:     R_LARCH_RELAX *ABS*
+# CHECKR-NEXT:   addi.d $a0, $a0, 0
+# CHECKR-NEXT:     R_LARCH_PCALA_LO12 _start
+# CHECKR-NEXT:     R_LARCH_RELAX *ABS*
+# CHECKR-NEXT:   nop
+# CHECKR-NEXT:     R_LARCH_ALIGN .Lla-relax-align0+0x4
+# CHECKR-NEXT:   nop
+# CHECKR-NEXT:   nop
+# CHECKR-NEXT:   ret
+
+.global _start
+_start:
+  la.pcrel $a0, _start
+  .p2align 4
+  ret
-- 
2.20.1