[MC] Write padding into fragments when -mc-relax-all flag is used

Summary:
When instruction bundling is enabled and the -mc-relax-all flag is
set, we can write bundle padding directly into fragments and avoid
creating large number of fragments significantly reducing LLVM MC
memory usage.

Test Plan: Regression test attached

Reviewers: eliben

Subscribers: jfb, mseaborn

Differential Revision: http://reviews.llvm.org/D8072

llvm-svn: 234714

include/llvm/MC/MCAsmLayout.h

@@ -50,11 +50,6 @@ private:
   /// \brief Is the layout for this fragment valid?
   bool isFragmentValid(const MCFragment *F) const;
 
-  /// \brief Compute the amount of padding required before this fragment to
-  /// obey bundling restrictions.
-  uint64_t computeBundlePadding(const MCFragment *F,
-                                uint64_t FOffset, uint64_t FSize);
-
 public:
   MCAsmLayout(MCAssembler &Assembler);
 

include/llvm/MC/MCAssembler.h

@@ -1245,11 +1245,23 @@ public:
       FileNames.push_back(FileName);
   }
 
+  /// \brief Write the necessary bundle padding to the given object writer.
+  /// Expects a fragment \p F containing instructions and its size \p FSize.
+  void writeFragmentPadding(const MCFragment &F, uint64_t FSize,
+                            MCObjectWriter *OW) const;
+
   /// @}
 
   void dump();
 };
 
+/// \brief Compute the amount of padding required before the fragment \p F to
+/// obey bundling restrictions, where \p FOffset is the fragment's offset in
+/// its section and \p FSize is the fragment's size.
+uint64_t computeBundlePadding(const MCAssembler &Assembler,
+                              const MCFragment *F,
+                              uint64_t FOffset, uint64_t FSize);
+
 } // end namespace llvm
 
 #endif

include/llvm/MC/MCELFStreamer.h

@@ -95,6 +95,9 @@ private:
 
   void fixSymbolsInTLSFixups(const MCExpr *expr);
 
+  /// \brief Merge the content of the fragment \p EF into the fragment \p DF.
+  void mergeFragment(MCDataFragment *, MCEncodedFragmentWithFixups *);
+
   bool SeenIdent;
 
   struct LocalCommon {
@@ -106,6 +109,10 @@ private:
   std::vector<LocalCommon> LocalCommons;
 
   SmallPtrSet<MCSymbol *, 16> BindingExplicitlySet;
+
+  /// BundleGroups - The stack of fragments holding the bundle-locked
+  /// instructions.
+  llvm::SmallVector<MCDataFragment *, 4> BundleGroups;
 };
 
 MCELFStreamer *createARMELFStreamer(MCContext &Context, MCAsmBackend &TAB,

include/llvm/MC/MCObjectStreamer.h

@@ -44,10 +44,6 @@ class MCObjectStreamer : public MCStreamer {
   void EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) override;
   void EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) override;
 
-  // If any labels have been emitted but not assigned fragments, ensure that
-  // they get assigned, either to F if possible or to a new data fragment.
-  void flushPendingLabels(MCFragment *F);
-
 protected:
   MCObjectStreamer(MCContext &Context, MCAsmBackend &TAB, raw_ostream &OS,
                    MCCodeEmitter *Emitter);
@@ -85,6 +81,12 @@ protected:
 
   bool changeSectionImpl(const MCSection *Section, const MCExpr *Subsection);
 
+  /// If any labels have been emitted but not assigned fragments, ensure that
+  /// they get assigned, either to F if possible or to a new data fragment.
+  /// Optionally, it is also possible to provide an offset \p FOffset, which
+  /// will be used as a symbol offset within the fragment.
+  void flushPendingLabels(MCFragment *F, uint64_t FOffset = 0);
+
 public:
   void visitUsedSymbol(const MCSymbol &Sym) override;
 

lib/MC/MCAssembler.cpp

@@ -229,8 +229,9 @@ uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
   return getSectionAddressSize(SD);
 }
 
-uint64_t MCAsmLayout::computeBundlePadding(const MCFragment *F,
-                                           uint64_t FOffset, uint64_t FSize) {
+uint64_t llvm::computeBundlePadding(const MCAssembler &Assembler,
+                                    const MCFragment *F,
+                                    uint64_t FOffset, uint64_t FSize) {
   uint64_t BundleSize = Assembler.getBundleAlignSize();
   assert(BundleSize > 0 &&
          "computeBundlePadding should only be called if bundling is enabled");
@@ -332,6 +333,7 @@ MCSectionData::getSubsectionInsertionPoint(unsigned Subsection) {
     getFragmentList().insert(IP, F);
     F->setParent(this);
   }
+
   return IP;
 }
 
@@ -632,7 +634,12 @@ void MCAsmLayout::layoutFragment(MCFragment *F) {
   // The fragment's offset will point to after the padding, and its computed
   // size won't include the padding.
   //
-  if (Assembler.isBundlingEnabled() && F->hasInstructions()) {
+  // When the -mc-relax-all flag is used, we optimize bundling by writting the
+  // bundle padding directly into fragments when the instructions are emitted
+  // inside the streamer.
+  //
+  if (Assembler.isBundlingEnabled() && !Assembler.getRelaxAll() &&
+      F->hasInstructions()) {
     assert(isa<MCEncodedFragment>(F) &&
            "Only MCEncodedFragment implementations have instructions");
     uint64_t FSize = Assembler.computeFragmentSize(*this, *F);
@@ -640,7 +647,8 @@ void MCAsmLayout::layoutFragment(MCFragment *F) {
     if (FSize > Assembler.getBundleAlignSize())
       report_fatal_error("Fragment can't be larger than a bundle size");
 
-    uint64_t RequiredBundlePadding = computeBundlePadding(F, F->Offset, FSize);
+    uint64_t RequiredBundlePadding = computeBundlePadding(Assembler, F,
+                                                          F->Offset, FSize);
     if (RequiredBundlePadding > UINT8_MAX)
       report_fatal_error("Padding cannot exceed 255 bytes");
     F->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
@@ -655,24 +663,18 @@ static void writeFragmentContents(const MCFragment &F, MCObjectWriter *OW) {
   OW->WriteBytes(EF.getContents());
 }
 
-/// \brief Write the fragment \p F to the output file.
-static void writeFragment(const MCAssembler &Asm, const MCAsmLayout &Layout,
-                          const MCFragment &F) {
-  MCObjectWriter *OW = &Asm.getWriter();
-
-  // FIXME: Embed in fragments instead?
-  uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
-
+void MCAssembler::writeFragmentPadding(const MCFragment &F, uint64_t FSize,
+                                       MCObjectWriter *OW) const {
   // Should NOP padding be written out before this fragment?
   unsigned BundlePadding = F.getBundlePadding();
   if (BundlePadding > 0) {
-    assert(Asm.isBundlingEnabled() &&
+    assert(isBundlingEnabled() &&
            "Writing bundle padding with disabled bundling");
     assert(F.hasInstructions() &&
            "Writing bundle padding for a fragment without instructions");
 
-    unsigned TotalLength = BundlePadding + static_cast<unsigned>(FragmentSize);
-    if (F.alignToBundleEnd() && TotalLength > Asm.getBundleAlignSize()) {
+    unsigned TotalLength = BundlePadding + static_cast<unsigned>(FSize);
+    if (F.alignToBundleEnd() && TotalLength > getBundleAlignSize()) {
       // If the padding itself crosses a bundle boundary, it must be emitted
       // in 2 pieces, since even nop instructions must not cross boundaries.
       //             v--------------v   <- BundleAlignSize
@@ -681,16 +683,27 @@ static void writeFragment(const MCAssembler &Asm, const MCAsmLayout &Layout,
       // | Prev |####|####|    F    |
       // ----------------------------
       //        ^-------------------^   <- TotalLength
-      unsigned DistanceToBoundary = TotalLength - Asm.getBundleAlignSize();
-      if (!Asm.getBackend().writeNopData(DistanceToBoundary, OW))
+      unsigned DistanceToBoundary = TotalLength - getBundleAlignSize();
+      if (!getBackend().writeNopData(DistanceToBoundary, OW))
           report_fatal_error("unable to write NOP sequence of " +
                              Twine(DistanceToBoundary) + " bytes");
       BundlePadding -= DistanceToBoundary;
     }
-    if (!Asm.getBackend().writeNopData(BundlePadding, OW))
+    if (!getBackend().writeNopData(BundlePadding, OW))
       report_fatal_error("unable to write NOP sequence of " +
                          Twine(BundlePadding) + " bytes");
   }
+}
+
+/// \brief Write the fragment \p F to the output file.
+static void writeFragment(const MCAssembler &Asm, const MCAsmLayout &Layout,
+                          const MCFragment &F) {
+  MCObjectWriter *OW = &Asm.getWriter();
+
+  // FIXME: Embed in fragments instead?
+  uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
+
+  Asm.writeFragmentPadding(F, FragmentSize, OW);
 
   // This variable (and its dummy usage) is to participate in the assert at
   // the end of the function.

lib/MC/MCELFStreamer.cpp

@@ -15,6 +15,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/MC/MCAsmBackend.h"
+#include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCCodeEmitter.h"
@@ -40,6 +41,48 @@ using namespace llvm;
 MCELFStreamer::~MCELFStreamer() {
 }
 
+void MCELFStreamer::mergeFragment(MCDataFragment *DF,
+                                  MCEncodedFragmentWithFixups *EF) {
+  MCAssembler &Assembler = getAssembler();
+
+  if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
+    uint64_t FSize = EF->getContents().size();
+
+    if (FSize > Assembler.getBundleAlignSize())
+      report_fatal_error("Fragment can't be larger than a bundle size");
+
+    uint64_t RequiredBundlePadding = computeBundlePadding(
+        Assembler, EF, DF->getContents().size(), FSize);
+
+    if (RequiredBundlePadding > UINT8_MAX)
+      report_fatal_error("Padding cannot exceed 255 bytes");
+
+    if (RequiredBundlePadding > 0) {
+      SmallString<256> Code;
+      raw_svector_ostream VecOS(Code);
+      MCObjectWriter *OW = Assembler.getBackend().createObjectWriter(VecOS);
+
+      EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
+
+      Assembler.writeFragmentPadding(*EF, FSize, OW);
+      VecOS.flush();
+      delete OW;
+
+      DF->getContents().append(Code.begin(), Code.end());
+    }
+  }
+
+  flushPendingLabels(DF, DF->getContents().size());
+
+  for (unsigned i = 0, e = EF->getFixups().size(); i != e; ++i) {
+    EF->getFixups()[i].setOffset(EF->getFixups()[i].getOffset() +
+                                 DF->getContents().size());
+    DF->getFixups().push_back(EF->getFixups()[i]);
+  }
+  DF->setHasInstructions(true);
+  DF->getContents().append(EF->getContents().begin(), EF->getContents().end());
+}
+
 void MCELFStreamer::InitSections(bool NoExecStack) {
   // This emulates the same behavior of GNU as. This makes it easier
   // to compare the output as the major sections are in the same order.
@@ -449,7 +492,16 @@ void MCELFStreamer::EmitInstToData(const MCInst &Inst,
 
   if (Assembler.isBundlingEnabled()) {
     MCSectionData *SD = getCurrentSectionData();
-    if (SD->isBundleLocked() && !SD->isBundleGroupBeforeFirstInst())
+    if (Assembler.getRelaxAll() && SD->isBundleLocked())
+      // If the -mc-relax-all flag is used and we are bundle-locked, we re-use
+      // the current bundle group.
+      DF = BundleGroups.back();
+    else if (Assembler.getRelaxAll() && !SD->isBundleLocked())
+      // When not in a bundle-locked group and the -mc-relax-all flag is used,
+      // we create a new temporary fragment which will be later merged into
+      // the current fragment.
+      DF = new MCDataFragment();
+    else if (SD->isBundleLocked() && !SD->isBundleGroupBeforeFirstInst())
       // If we are bundle-locked, we re-use the current fragment.
       // The bundle-locking directive ensures this is a new data fragment.
       DF = cast<MCDataFragment>(getCurrentFragment());
@@ -487,6 +539,14 @@ void MCELFStreamer::EmitInstToData(const MCInst &Inst,
   }
   DF->setHasInstructions(true);
   DF->getContents().append(Code.begin(), Code.end());
+
+  if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
+    MCSectionData *SD = getCurrentSectionData();
+    if (!SD->isBundleLocked()) {
+      mergeFragment(getOrCreateDataFragment(), DF);
+      delete DF;
+    }
+  }
 }
 
 void MCELFStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
@@ -510,6 +570,12 @@ void MCELFStreamer::EmitBundleLock(bool AlignToEnd) {
   if (!SD->isBundleLocked())
     SD->setBundleGroupBeforeFirstInst(true);
 
+  if (getAssembler().getRelaxAll() && !SD->isBundleLocked()) {
+    // TODO: drop the lock state and set directly in the fragment
+    MCDataFragment *DF = new MCDataFragment();
+    BundleGroups.push_back(DF);
+  }
+
   SD->setBundleLockState(AlignToEnd ? MCSectionData::BundleLockedAlignToEnd :
                                       MCSectionData::BundleLocked);
 }
@@ -525,7 +591,27 @@ void MCELFStreamer::EmitBundleUnlock() {
   else if (SD->isBundleGroupBeforeFirstInst())
     report_fatal_error("Empty bundle-locked group is forbidden");
 
-  SD->setBundleLockState(MCSectionData::NotBundleLocked);
+  // When the -mc-relax-all flag is used, we emit instructions to fragments
+  // stored on a stack. When the bundle unlock is emited, we pop a fragment 
+  // from the stack a merge it to the one below.
+  if (getAssembler().getRelaxAll()) {
+    assert(!BundleGroups.empty() && "There are no bundle groups");
+    MCDataFragment *DF = BundleGroups.back();
+
+    // FIXME: Use BundleGroups to track the lock state instead.
+    SD->setBundleLockState(MCSectionData::NotBundleLocked);
+
+    // FIXME: Use more separate fragments for nested groups. 
+    if (!SD->isBundleLocked()) {
+      mergeFragment(getOrCreateDataFragment(), DF);
+      BundleGroups.pop_back();
+      delete DF;
+    }
+
+    if (SD->getBundleLockState() != MCSectionData::BundleLockedAlignToEnd)
+      getOrCreateDataFragment()->setAlignToBundleEnd(false);
+  } else
+    SD->setBundleLockState(MCSectionData::NotBundleLocked);
 }
 
 void MCELFStreamer::Flush() {

lib/MC/MCObjectStreamer.cpp

@@ -37,7 +37,7 @@ MCObjectStreamer::~MCObjectStreamer() {
   delete Assembler;
 }
 
-void MCObjectStreamer::flushPendingLabels(MCFragment *F) {
+void MCObjectStreamer::flushPendingLabels(MCFragment *F, uint64_t FOffset) {
   if (PendingLabels.size()) {
     if (!F) {
       F = new MCDataFragment();
@@ -46,7 +46,7 @@ void MCObjectStreamer::flushPendingLabels(MCFragment *F) {
     }
     for (MCSymbolData *SD : PendingLabels) {
       SD->setFragment(F);
-      SD->setOffset(0);
+      SD->setOffset(FOffset);
     }
     PendingLabels.clear();
   }
@@ -87,7 +87,8 @@ MCDataFragment *MCObjectStreamer::getOrCreateDataFragment() {
   MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
   // When bundling is enabled, we don't want to add data to a fragment that
   // already has instructions (see MCELFStreamer::EmitInstToData for details)
-  if (!F || (Assembler->isBundlingEnabled() && F->hasInstructions())) {
+  if (!F || (Assembler->isBundlingEnabled() && !Assembler->getRelaxAll() &&
+             F->hasInstructions())) {
     F = new MCDataFragment();
     insert(F);
   }
@@ -143,7 +144,9 @@ void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) {
   // If there is a current fragment, mark the symbol as pointing into it.
   // Otherwise queue the label and set its fragment pointer when we emit the
   // next fragment.
-  if (auto *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment())) {
+  auto *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
+  if (F && !(getAssembler().isBundlingEnabled() &&
+             getAssembler().getRelaxAll())) {
     SD.setFragment(F);
     SD.setOffset(F->getContents().size());
   } else {
@@ -242,6 +245,9 @@ void MCObjectStreamer::EmitInstruction(const MCInst &Inst,
 
 void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst,
                                           const MCSubtargetInfo &STI) {
+  if (getAssembler().getRelaxAll() && getAssembler().isBundlingEnabled())
+    llvm_unreachable("All instructions should have already been relaxed");
+
   // Always create a new, separate fragment here, because its size can change
   // during relaxation.
   MCRelaxableFragment *IF = new MCRelaxableFragment(Inst, STI);

test/MC/X86/AlignedBundling/bundle-group-too-large-error.s

@@ -1,4 +1,5 @@
 # RUN: not llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - 2>&1 | FileCheck %s
+# RUN: not llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu -mc-relax-all %s -o - 2>&1 | FileCheck %s
 
 # CHECK: ERROR: Fragment can't be larger than a bundle size
 

test/MC/X86/AlignedBundling/different-sections.s

@@ -1,5 +1,7 @@
 # RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - \
 # RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu -mc-relax-all %s -o - \
+# RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
 
 # Test two different executable sections with bundling.
 

test/MC/X86/AlignedBundling/labeloffset.s

@@ -1,6 +1,8 @@
 # RUN: llvm-mc -triple=i686-linux -filetype=obj %s -o - | \
 # RUN: llvm-objdump -disassemble -no-show-raw-insn -r - | FileCheck %s
 # RUN: llvm-mc -triple=i686-nacl -filetype=obj %s -o - | \
+# RUN: llvm-objdump -disassemble -no-show-raw-insn -r - | FileCheck %s
+# RUN: llvm-mc -triple=i686-nacl -filetype=obj -mc-relax-all %s -o - | \
 # RUN: llvm-objdump -disassemble -no-show-raw-insn -r - | FileCheck %s
 
         .bundle_align_mode 5

test/MC/X86/AlignedBundling/long-nop-pad.s

@@ -1,5 +1,7 @@
 # RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - \
 # RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu -mc-relax-all %s -o - \
+# RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
 
 # Test that long nops are generated for padding where possible.
 

test/MC/X86/AlignedBundling/nesting.s

@@ -1,5 +1,7 @@
 # RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - \
 # RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu -mc-relax-all %s -o - \
+# RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
 
 # Will be bundle-aligning to 16 byte boundaries
   .bundle_align_mode 4

test/MC/X86/AlignedBundling/pad-align-to-bundle-end.s

@@ -1,5 +1,7 @@
 # RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - \
 # RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu -mc-relax-all %s -o - \
+# RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
 
 # Test some variations of padding to the end of a bundle.
 

test/MC/X86/AlignedBundling/pad-bundle-groups.s

@@ -1,5 +1,7 @@
 # RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - \
 # RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu -mc-relax-all %s -o - \
+# RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
 
 # Test some variations of padding for bundle-locked groups.
 

test/MC/X86/AlignedBundling/relax-at-bundle-end.s

@@ -1,5 +1,7 @@
 # RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - \
 # RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu -mc-relax-all %s -o - \
+# RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
 
 # Test that an instruction near a bundle end gets properly padded
 # after it is relaxed.

test/MC/X86/AlignedBundling/relax-in-bundle-group.s

@@ -1,5 +1,7 @@
 # RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - \
 # RUN:   | llvm-objdump -disassemble - | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu -mc-relax-all %s -o - \
+# RUN:   | llvm-objdump -disassemble - | FileCheck %s
 
 # Test that instructions inside bundle-locked groups are relaxed even if their
 # fixup is short enough not to warrant relaxation on its own.

test/MC/X86/AlignedBundling/single-inst-bundling.s

@@ -1,5 +1,7 @@
 # RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - \
-# RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck %s
+# RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck -check-prefix=CHECK -check-prefix=CHECK-OPT %s
+# RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu -mc-relax-all %s -o - \
+# RUN:   | llvm-objdump -disassemble -no-show-raw-insn - | FileCheck -check-prefix=CHECK -check-prefix=CHECK-RELAX %s
 
 # Test simple NOP insertion for single instructions.
 
@@ -24,14 +26,17 @@ foo:
   movl    %ebx, %edi
   callq   bar
   cmpl    %r14d, %ebp
+# CHECK-RELAX:   nopl
   jle     .L_ELSE
 # Due to the padding that's inserted before the addl, the jump target
 # becomes farther by one byte.
-# CHECK:         jle 5
+# CHECK-OPT:     jle 5
+# CHECK-RELAX:   jle 7
 
   addl    %ebp, %eax
-# CHECK:          nop
-# CHECK-NEXT:     20: addl
+# CHECK-OPT:     nop
+# CHECK-OPT-NEXT:20: addl
+# CHECK-RELAX:   26: addl
 
   jmp     .L_RET
 .L_ELSE: