Add a helper method that will be used to support EXTRACT_SUBREG for selecting trunc's in fast-isel.

llvm-svn: 55439

2 files changed, 16 insertions, 0 deletions

diff --git a/llvm/include/llvm/CodeGen/FastISel.h b/llvm/include/llvm/CodeGen/FastISel.h
index f28739448df..fcd970b8404 100644
--- a/llvm/include/llvm/CodeGen/FastISel.h
+++ b/llvm/include/llvm/CodeGen/FastISel.h
@@ -193,6 +193,11 @@ protected:
                           const TargetRegisterClass *RC,
                           uint64_t Imm);
 
+  /// FastEmitInst_extractsubreg - Emit a MachineInstr for an extract_subreg
+  /// from a specified index of a superregister.
+  unsigned FastEmitInst_extractsubreg(const TargetRegisterClass *RC,
+                                      unsigned Op0, uint32_t Idx);
+
 private:
   unsigned getRegForValue(Value *V,
                           DenseMap<const Value*, unsigned> &ValueMap);
diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
index 82eee56cd2b..2dd228249b3 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -586,3 +586,14 @@ unsigned FastISel::FastEmitInst_i(unsigned MachineInstOpcode,
   BuildMI(MBB, II, ResultReg).addImm(Imm);
   return ResultReg;
 }
+
+unsigned FastISel::FastEmitInst_extractsubreg(const TargetRegisterClass *RC,
+                                              unsigned Op0, uint32_t Idx) {
+  const TargetRegisterClass* SRC = *(RC->subregclasses_begin()+Idx-1);
+  
+  unsigned ResultReg = createResultReg(SRC);
+  const TargetInstrDesc &II = TII.get(TargetInstrInfo::EXTRACT_SUBREG);
+  
+  BuildMI(MBB, II, ResultReg).addReg(Op0);
+  return ResultReg;
+}