Add support for long branches

include/llvm/CodeGen/Passes.h

@@ -181,6 +181,10 @@ namespace llvm {
   /// branches.
   extern char &BranchFolderPassID;
 
+  /// BranchRelaxation - This pass replaces branches that need to jump further
+  /// than is supported by a branch instruction.
+  extern char &BranchRelaxationPassID;
+
   /// MachineFunctionPrinterPass - This pass prints out MachineInstr's.
   extern char &MachineFunctionPrinterPassID;
 

include/llvm/InitializePasses.h

@@ -79,6 +79,7 @@ void initializeBlockFrequencyInfoWrapperPassPass(PassRegistry&);
 void initializeBoundsCheckingPass(PassRegistry&);
 void initializeBranchFolderPassPass(PassRegistry&);
 void initializeBranchProbabilityInfoWrapperPassPass(PassRegistry&);
+void initializeBranchRelaxationPass(PassRegistry&);
 void initializeBreakCriticalEdgesPass(PassRegistry&);
 void initializeCFGOnlyViewerLegacyPassPass(PassRegistry&);
 void initializeCFGPrinterLegacyPassPass(PassRegistry&);

include/llvm/Target/TargetInstrInfo.h

@@ -443,6 +443,31 @@ class TargetInstrInfo : public MCInstrInfo {
                                 const MachineInstr &MI1,
                                 const MachineRegisterInfo *MRI = nullptr) const;
 
+  /// \returns true if a branch from an instruction with opcode \p BranchOpc
+  ///  bytes is capable of jumping to a position \p BrOffset bytes away.
+  virtual bool isBranchOffsetInRange(unsigned BranchOpc,
+                                     int64_t BrOffset) const {
+    llvm_unreachable("target did not implement");
+  }
+
+  /// \returns The block that branch instruction \p MI jumps to.
+  virtual MachineBasicBlock *getBranchDestBlock(const MachineInstr &MI) const {
+    llvm_unreachable("target did not implement");
+  }
+
+  /// Insert an unconditional indirect branch at the end of \p MBB to \p
+  /// NewDestBB.  \p BrOffset indicates the offset of \p NewDestBB relative to
+  /// the offset of the position to insert the new branch.
+  ///
+  /// \returns The number of bytes added to the block.
+  virtual unsigned insertIndirectBranch(MachineBasicBlock &MBB,
+                                        MachineBasicBlock &NewDestBB,
+                                        const DebugLoc &DL,
+                                        int64_t BrOffset = 0,
+                                        RegScavenger *RS = nullptr) const {
+    llvm_unreachable("target did not implement");
+  }
+
   /// Analyze the branching code at the end of MBB, returning
   /// true if it cannot be understood (e.g. it's a switch dispatch or isn't
   /// implemented for a target).  Upon success, this returns false and returns