implement the new addressing mode description hook.

llvm-svn: 35521
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 0d5b693..4b29bc7 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -3199,6 +3199,39 @@
   return TargetLowering::isOperandValidForConstraint(Op, Letter, DAG);
 }
 
+// isLegalAddressingMode - Return true if the addressing mode represented
+// by AM is legal for this target, for a load/store of the specified type.
+bool PPCTargetLowering::isLegalAddressingMode(const AddrMode &AM, 
+                                              const Type *Ty) const {
+  // FIXME: PPC does not allow r+i addressing modes for vectors!
+  
+  // PPC allows a sign-extended 16-bit immediate field.
+  if (AM.BaseOffs <= -(1LL << 16) || AM.BaseOffs >= (1LL << 16)-1)
+    return false;
+  
+  // No global is ever allowed as a base.
+  if (AM.BaseGV)
+    return false;
+  
+  // PPC only support r+r, 
+  switch (AM.Scale) {
+  case 0:  // "r+i" or just "i", depending on HasBaseReg.
+    break;
+  case 1:
+    if (AM.HasBaseReg && AM.BaseOffs)  // "r+r+i" is not allowed.
+      return false;
+    // Otherwise we have r+r or r+i.
+    break;
+  case 2:
+    if (AM.HasBaseReg || AM.BaseOffs)  // 2*r+r  or  2*r+i is not allowed.
+      return false;
+    // Allow 2*r as r+r.
+    break;
+  }
+  
+  return true;
+}
+
 /// isLegalAddressImmediate - Return true if the integer value can be used
 /// as the offset of the target addressing mode for load / store of the
 /// given type.
@@ -3208,7 +3241,7 @@
 }
 
 bool PPCTargetLowering::isLegalAddressImmediate(llvm::GlobalValue* GV) const {
-  return TargetLowering::isLegalAddressImmediate(GV); 
+  return false; 
 }
 
 SDOperand PPCTargetLowering::LowerFRAMEADDR(SDOperand Op, SelectionDAG &DAG)
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.h b/llvm/lib/Target/PowerPC/PPCISelLowering.h
index e66d165..593400c 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.h
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.h
@@ -236,6 +236,10 @@
     SDOperand isOperandValidForConstraint(SDOperand Op, char ConstraintLetter,
                                           SelectionDAG &DAG);
 
+    /// isLegalAddressingMode - Return true if the addressing mode represented
+    /// by AM is legal for this target, for a load/store of the specified type.
+    virtual bool isLegalAddressingMode(const AddrMode &AM, const Type *Ty)const;
+    
     /// isLegalAddressImmediate - Return true if the integer value can be used
     /// as the offset of the target addressing mode for load / store of the
     /// given type.