Eliminate target hook IsEligibleForTailCallOptimization.

Target independent isel should always pass along the "tail call" property. Change
target hook LowerCall's parameter "isTailCall" into a refernce. If the target
decides it's impossible to honor the tail call request, it should set isTailCall
to false to make target independent isel happy.

llvm-svn: 94626
diff --git a/llvm/lib/Target/Alpha/AlphaISelLowering.cpp b/llvm/lib/Target/Alpha/AlphaISelLowering.cpp
index 399c224..0bbe567 100644
--- a/llvm/lib/Target/Alpha/AlphaISelLowering.cpp
+++ b/llvm/lib/Target/Alpha/AlphaISelLowering.cpp
@@ -221,11 +221,13 @@
 SDValue
 AlphaTargetLowering::LowerCall(SDValue Chain, SDValue Callee,
                                CallingConv::ID CallConv, bool isVarArg,
-                               bool isTailCall,
+                               bool &isTailCall,
                                const SmallVectorImpl<ISD::OutputArg> &Outs,
                                const SmallVectorImpl<ISD::InputArg> &Ins,
                                DebugLoc dl, SelectionDAG &DAG,
                                SmallVectorImpl<SDValue> &InVals) {
+  // Alpha target does not yet support tail call optimization.
+  isTailCall = false;
 
   // Analyze operands of the call, assigning locations to each operand.
   SmallVector<CCValAssign, 16> ArgLocs;
diff --git a/llvm/lib/Target/Alpha/AlphaISelLowering.h b/llvm/lib/Target/Alpha/AlphaISelLowering.h
index b204faf..0f17025 100644
--- a/llvm/lib/Target/Alpha/AlphaISelLowering.h
+++ b/llvm/lib/Target/Alpha/AlphaISelLowering.h
@@ -121,7 +121,7 @@
 
     virtual SDValue
       LowerCall(SDValue Chain, SDValue Callee,
-                CallingConv::ID CallConv, bool isVarArg, bool isTailCall,
+                CallingConv::ID CallConv, bool isVarArg, bool &isTailCall,
                 const SmallVectorImpl<ISD::OutputArg> &Outs,
                 const SmallVectorImpl<ISD::InputArg> &Ins,
                 DebugLoc dl, SelectionDAG &DAG,