4 files changed, 31 insertions, 12 deletions

diff --git a/llvm/include/llvm/MC/MCAsmBackend.h b/llvm/include/llvm/MC/MCAsmBackend.h
index 1272829b1f6..030d3c05aa5 100644
--- a/llvm/include/llvm/MC/MCAsmBackend.h
+++ b/llvm/include/llvm/MC/MCAsmBackend.h
@@ -92,9 +92,12 @@ public:
   /// the offset specified by the fixup and following the fixup kind as
   /// appropriate. Errors (such as an out of range fixup value) should be
   /// reported via \p Ctx.
+  /// The  \p STI is present only for fragments of type MCRelaxableFragment and
+  /// MCDataFragment with hasInstructions() == true.
   virtual void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
                           const MCValue &Target, MutableArrayRef<char> Data,
-                          uint64_t Value, bool IsResolved) const = 0;
+                          uint64_t Value, bool IsResolved,
+                          const MCSubtargetInfo *STI) const = 0;
 
   /// Check whether the given target requires emitting differences of two
   /// symbols as a set of relocations.
@@ -108,7 +111,10 @@ public:
   /// Check whether the given instruction may need relaxation.
   ///
   /// \param Inst - The instruction to test.
-  virtual bool mayNeedRelaxation(const MCInst &Inst) const = 0;
+  /// \param STI - The MCSubtargetInfo in effect when the instruction was
+  /// encoded.
+  virtual bool mayNeedRelaxation(const MCInst &Inst,
+                                 const MCSubtargetInfo &STI) const = 0;
 
   /// Target specific predicate for whether a given fixup requires the
   /// associated instruction to be relaxed.
diff --git a/llvm/include/llvm/MC/MCFragment.h b/llvm/include/llvm/MC/MCFragment.h
index 95878f81c86..16eb124d95e 100644
--- a/llvm/include/llvm/MC/MCFragment.h
+++ b/llvm/include/llvm/MC/MCFragment.h
@@ -201,7 +201,16 @@ protected:
       : MCEncodedFragmentWithContents<ContentsSize>(FType, HasInstructions,
                                                     Sec) {}
 
+  /// STI - The MCSubtargetInfo in effect when the instruction was encoded.
+  /// must be non-null for instructions.
+  const MCSubtargetInfo *STI = nullptr;
+
 public:
+
+  /// Retrieve the MCSubTargetInfo in effect when the instruction was encoded.
+  /// Guaranteed to be non-null if hasInstructions() == true
+  const MCSubtargetInfo *getSubtargetInfo() const { return STI; }
+
   using const_fixup_iterator = SmallVectorImpl<MCFixup>::const_iterator;
   using fixup_iterator = SmallVectorImpl<MCFixup>::iterator;
 
@@ -228,7 +237,12 @@ public:
   MCDataFragment(MCSection *Sec = nullptr)
       : MCEncodedFragmentWithFixups<32, 4>(FT_Data, false, Sec) {}
 
-  void setHasInstructions(bool V) { HasInstructions = V; }
+  /// Record that the fragment contains instructions with the MCSubtargetInfo in
+  /// effect when the instruction was encoded.
+  void setHasInstructions(const MCSubtargetInfo &STI) {
+    HasInstructions = true;
+    this->STI = &STI;
+  }
 
   static bool classof(const MCFragment *F) {
     return F->getKind() == MCFragment::FT_Data;
@@ -259,20 +273,15 @@ class MCRelaxableFragment : public MCEncodedFragmentWithFixups<8, 1> {
   /// Inst - The instruction this is a fragment for.
   MCInst Inst;
 
-  /// STI - The MCSubtargetInfo in effect when the instruction was encoded.
-  const MCSubtargetInfo &STI;
-
 public:
   MCRelaxableFragment(const MCInst &Inst, const MCSubtargetInfo &STI,
                       MCSection *Sec = nullptr)
       : MCEncodedFragmentWithFixups(FT_Relaxable, true, Sec),
-        Inst(Inst), STI(STI) {}
+        Inst(Inst) { this->STI = &STI; }
 
   const MCInst &getInst() const { return Inst; }
   void setInst(const MCInst &Value) { Inst = Value; }
 
-  const MCSubtargetInfo &getSubtargetInfo() { return STI; }
-
   static bool classof(const MCFragment *F) {
     return F->getKind() == MCFragment::FT_Relaxable;
   }
diff --git a/llvm/include/llvm/MC/MCObjectStreamer.h b/llvm/include/llvm/MC/MCObjectStreamer.h
index 498a8af9011..8715a16e705 100644
--- a/llvm/include/llvm/MC/MCObjectStreamer.h
+++ b/llvm/include/llvm/MC/MCObjectStreamer.h
@@ -73,7 +73,9 @@ public:
 
   /// Get a data fragment to write into, creating a new one if the current
   /// fragment is not a data fragment.
-  MCDataFragment *getOrCreateDataFragment();
+  /// Optionally a \p STI can be passed in so that a new fragment is created
+  /// if the Subtarget differs from the current fragment.
+  MCDataFragment *getOrCreateDataFragment(const MCSubtargetInfo* STI = nullptr);
   MCPaddingFragment *getOrCreatePaddingFragment();
 
 protected:
@@ -158,7 +160,8 @@ public:
   void EmitGPRel32Value(const MCExpr *Value) override;
   void EmitGPRel64Value(const MCExpr *Value) override;
   bool EmitRelocDirective(const MCExpr &Offset, StringRef Name,
-                          const MCExpr *Expr, SMLoc Loc) override;
+                          const MCExpr *Expr, SMLoc Loc,
+                          const MCSubtargetInfo &STI) override;
   using MCStreamer::emitFill;
   void emitFill(const MCExpr &NumBytes, uint64_t FillValue,
                 SMLoc Loc = SMLoc()) override;
diff --git a/llvm/include/llvm/MC/MCStreamer.h b/llvm/include/llvm/MC/MCStreamer.h
index db4f885a7d9..43712de727b 100644
--- a/llvm/include/llvm/MC/MCStreamer.h
+++ b/llvm/include/llvm/MC/MCStreamer.h
@@ -918,7 +918,8 @@ public:
   /// Returns true if the relocation could not be emitted because Name is not
   /// known.
   virtual bool EmitRelocDirective(const MCExpr &Offset, StringRef Name,
-                                  const MCExpr *Expr, SMLoc Loc) {
+                                  const MCExpr *Expr, SMLoc Loc,
+                                  const MCSubtargetInfo &STI) {
     return true;
   }