5 files changed, 29 insertions, 15 deletions

diff --git a/include/llvm/MC/MCDwarf.h b/include/llvm/MC/MCDwarf.h
index 785f42d2f9d7..2bfaf19cf2c6 100644
--- a/include/llvm/MC/MCDwarf.h
+++ b/include/llvm/MC/MCDwarf.h
@@ -362,6 +362,13 @@ public:
   static void Encode(MCContext &Context, MCDwarfLineTableParams Params,
                      int64_t LineDelta, uint64_t AddrDelta, raw_ostream &OS);
 
+  /// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas using
+  /// fixed length operands.
+  static bool FixedEncode(MCContext &Context,
+                          MCDwarfLineTableParams Params,
+                          int64_t LineDelta, uint64_t AddrDelta,
+                          raw_ostream &OS, uint32_t *Offset, uint32_t *Size);
+
   /// Utility function to emit the encoding to a streamer.
   static void Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
                    int64_t LineDelta, uint64_t AddrDelta);
diff --git a/include/llvm/MC/MCFragment.h b/include/llvm/MC/MCFragment.h
index 47b35175fec8..c999c9fc4f17 100644
--- a/include/llvm/MC/MCFragment.h
+++ b/include/llvm/MC/MCFragment.h
@@ -149,6 +149,7 @@ public:
     case MCFragment::FT_Relaxable:
     case MCFragment::FT_CompactEncodedInst:
     case MCFragment::FT_Data:
+    case MCFragment::FT_Dwarf:
       return true;
     }
   }
@@ -232,7 +233,7 @@ public:
   static bool classof(const MCFragment *F) {
     MCFragment::FragmentType Kind = F->getKind();
     return Kind == MCFragment::FT_Relaxable || Kind == MCFragment::FT_Data ||
-           Kind == MCFragment::FT_CVDefRange;
+           Kind == MCFragment::FT_CVDefRange || Kind == MCFragment::FT_Dwarf;;
   }
 };
 
@@ -514,7 +515,7 @@ public:
   }
 };
 
-class MCDwarfLineAddrFragment : public MCFragment {
+class MCDwarfLineAddrFragment : public MCEncodedFragmentWithFixups<8, 1> {
   /// LineDelta - the value of the difference between the two line numbers
   /// between two .loc dwarf directives.
   int64_t LineDelta;
@@ -523,15 +524,11 @@ class MCDwarfLineAddrFragment : public MCFragment {
   /// make up the address delta between two .loc dwarf directives.
   const MCExpr *AddrDelta;
 
-  SmallString<8> Contents;
-
 public:
   MCDwarfLineAddrFragment(int64_t LineDelta, const MCExpr &AddrDelta,
                           MCSection *Sec = nullptr)
-      : MCFragment(FT_Dwarf, false, Sec), LineDelta(LineDelta),
-        AddrDelta(&AddrDelta) {
-    Contents.push_back(0);
-  }
+      : MCEncodedFragmentWithFixups<8, 1>(FT_Dwarf, false, Sec),
+        LineDelta(LineDelta), AddrDelta(&AddrDelta) {}
 
   /// \name Accessors
   /// @{
@@ -540,9 +537,6 @@ public:
 
   const MCExpr &getAddrDelta() const { return *AddrDelta; }
 
-  SmallString<8> &getContents() { return Contents; }
-  const SmallString<8> &getContents() const { return Contents; }
-
   /// @}
 
   static bool classof(const MCFragment *F) {
diff --git a/include/llvm/MC/MCInstrAnalysis.h b/include/llvm/MC/MCInstrAnalysis.h
index 484f03b4d854..e1673208d875 100644
--- a/include/llvm/MC/MCInstrAnalysis.h
+++ b/include/llvm/MC/MCInstrAnalysis.h
@@ -64,7 +64,7 @@ public:
 
   /// Returns true if at least one of the register writes performed by
   /// \param Inst implicitly clears the upper portion of all super-registers.
-  /// 
+  ///
   /// Example: on X86-64, a write to EAX implicitly clears the upper half of
   /// RAX. Also (still on x86) an XMM write perfomed by an AVX 128-bit
   /// instruction implicitly clears the upper portion of the correspondent
@@ -87,6 +87,19 @@ public:
                                     const MCInst &Inst,
                                     APInt &Writes) const;
 
+  /// Returns true if \param Inst is a dependency breaking instruction for the
+  /// given subtarget.
+  ///
+  /// The value computed by a dependency breaking instruction is not dependent
+  /// on the inputs. An example of dependency breaking instruction on X86 is
+  /// `XOR %eax, %eax`.
+  /// TODO: In future, we could implement an alternative approach where this
+  /// method returns `true` if the input instruction is not dependent on
+  /// some/all of its input operands. An APInt mask could then be used to
+  /// identify independent operands.
+  virtual bool isDependencyBreaking(const MCSubtargetInfo &STI,
+                                    const MCInst &Inst) const;
+
   /// Given a branch instruction try to get the address the branch
   /// targets. Return true on success, and the address in Target.
   virtual bool
diff --git a/include/llvm/MC/MCParser/AsmCond.h b/include/llvm/MC/MCParser/AsmCond.h
index 8e7bfc521556..a6e0fbd7f337 100644
--- a/include/llvm/MC/MCParser/AsmCond.h
+++ b/include/llvm/MC/MCParser/AsmCond.h
@@ -15,7 +15,7 @@ namespace llvm {
 /// AsmCond - Class to support conditional assembly
 ///
 /// The conditional assembly feature (.if, .else, .elseif and .endif) is
-/// implemented with AsmCond that tells us what we are in the middle of 
+/// implemented with AsmCond that tells us what we are in the middle of
 /// processing.  Ignore can be either true or false.  When true we are ignoring
 /// the block of code in the middle of a conditional.
 
diff --git a/include/llvm/MC/MCStreamer.h b/include/llvm/MC/MCStreamer.h
index 0a5d80c6d778..e4d0dc03b87c 100644
--- a/include/llvm/MC/MCStreamer.h
+++ b/include/llvm/MC/MCStreamer.h
@@ -297,8 +297,8 @@ public:
   /// If the comment includes embedded \n's, they will each get the comment
   /// prefix as appropriate.  The added comment should not end with a \n.
   /// By default, each comment is terminated with an end of line, i.e. the
-  /// EOL param is set to true by default. If one prefers not to end the 
-  /// comment with a new line then the EOL param should be passed 
+  /// EOL param is set to true by default. If one prefers not to end the
+  /// comment with a new line then the EOL param should be passed
   /// with a false value.
   virtual void AddComment(const Twine &T, bool EOL = true) {}