- Remove Tilmann's custom truncate lowering: it completely hosed over

DAGcombine's ability to find reasons to remove truncates when they were not
  needed. Consequently, the CellSPU backend would produce correct, but _really
  slow and horrible_, code.

  Replaced with instruction sequences that do the equivalent truncation in
  SPUInstrInfo.td.

- Re-examine how unaligned loads and stores work. Generated unaligned
  load code has been tested on the CellSPU hardware; see the i32operations.c
  and i64operations.c in CodeGen/CellSPU/useful-harnesses.  (While they may be
  toy test code, it does prove that some real world code does compile
  correctly.)

- Fix truncating stores in bug 3193 (note: unpack_df.ll will still make llc
  fault because i64 ult is not yet implemented.)

- Added i64 eq and neq for setcc and select/setcc; started new instruction
  information file for them in SPU64InstrInfo.td. Additional i64 operations
  should be added to this file and not to SPUInstrInfo.td.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61447 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/CellSPU/SPUISelLowering.h

@@ -39,7 +39,7 @@ namespace llvm {
       SHUFB,                    ///< Vector shuffle (permute)
       SHUFFLE_MASK,             ///< Shuffle mask
       CNTB,                     ///< Count leading ones in bytes
-      PROMOTE_SCALAR,           ///< Promote scalar->vector
+      PREFSLOT2VEC,             ///< Promote scalar->vector
       VEC2PREFSLOT,             ///< Extract element 0
       MPY,                      ///< 16-bit Multiply (low parts of a 32-bit)
       MPYU,                     ///< Multiply Unsigned
@@ -58,6 +58,7 @@ namespace llvm {
       ROTBYTES_LEFT_BITS,       ///< Rotate bytes left by bit shift count
       SELECT_MASK,              ///< Select Mask (FSM, FSMB, FSMH, FSMBI)
       SELB,                     ///< Select bits -> (b & mask) | (a & ~mask)
+      GATHER_BITS,              ///< Gather bits from bytes/words/halfwords
       ADD_EXTENDED,             ///< Add extended, with carry
       CARRY_GENERATE,           ///< Carry generate for ADD_EXTENDED
       SUB_EXTENDED,             ///< Subtract extended, with borrow
@@ -120,6 +121,9 @@ namespace llvm {
                                                 const SelectionDAG &DAG,
                                                 unsigned Depth = 0) const;
 
+    virtual unsigned ComputeNumSignBitsForTargetNode(SDValue Op,
+                                                   unsigned Depth = 0) const;
+
     ConstraintType getConstraintType(const std::string &ConstraintLetter) const;
 
     std::pair<unsigned, const TargetRegisterClass*>