Implement two virtual functions in SPUTargetLowering.

Before the implementation of isLegalAddressingMode, some rare cases 
of code were miscompiled if optimized with the LoopStrengthReduce pass.
It is unclear (to me) if LSR is "allowed" to produce wrong code with a 
bad TargetLowering, or if the bug is elsewhere and this patch just 
hides it.

llvm-svn: 115919

lib/Target/CellSPU/SPUISelLowering.cpp

@@ -3088,3 +3088,29 @@ SPUTargetLowering::isOffsetFoldingLegal(const GlobalAddressSDNode *GA) const {
   // The SPU target isn't yet aware of offsets.
   return false;
 }
+
+// can we compare to Imm without writing it into a register?
+bool SPUTargetLowering::isLegalICmpImmediate(int64_t Imm) const {
+  //ceqi, cgti, etc. all take s10 operand
+  return isInt<10>(Imm);
+}
+
+bool 
+SPUTargetLowering::isLegalAddressingMode(const AddrMode &AM, 
+                                         const Type * ) const{
+
+  // A-form: 18bit absolute address. 
+  if (AM.BaseGV && !AM.HasBaseReg && AM.Scale == 0 && AM.BaseOffs == 0)
+    return true;
+ 
+  // D-form: reg + 14bit offset
+  if (AM.BaseGV ==0 && AM.HasBaseReg && AM.Scale == 0 && isInt<14>(AM.BaseOffs))
+    return true;
+
+  // X-form: reg+reg
+  if (AM.BaseGV == 0 && AM.HasBaseReg && AM.Scale == 1 && AM.BaseOffs ==0)
+    return true;
+
+  return false;
+}
+

lib/Target/CellSPU/SPUISelLowering.h

@@ -170,6 +170,11 @@ namespace llvm {
                   const SmallVectorImpl<ISD::OutputArg> &Outs,
                   const SmallVectorImpl<SDValue> &OutVals,
                   DebugLoc dl, SelectionDAG &DAG) const;
+
+    virtual bool isLegalICmpImmediate(int64_t Imm) const;
+
+    virtual bool isLegalAddressingMode(const AddrMode &AM, 
+                                       const Type *Ty) const;
   };
 }