Index: lib/Target/PowerPC/PPCISelLowering.cpp
===================================================================
--- lib/Target/PowerPC/PPCISelLowering.cpp
+++ lib/Target/PowerPC/PPCISelLowering.cpp
@@ -5151,10 +5151,30 @@
   };
 
   const unsigned NumGPRs = array_lengthof(GPR);
-  const unsigned NumFPRs = 13;
+  const unsigned NumFPRs = useSoftFloat() ? 0 : 13;
   const unsigned NumVRs  = array_lengthof(VR);
   const unsigned NumQFPRs = NumFPRs;
 
+  // On ELFv2, we can avoid allocating the parameter area if all the arguments 
+  // can be passed to the callee in registers.
+  // For the fast calling convention, there is another check below.
+  // Note: keep consistent with LowerFormalArguments_64SVR4()
+  bool HasParameterArea = !isELFv2ABI || isVarArg;
+  if (!HasParameterArea && CallConv != CallingConv::Fast) {
+    unsigned ParamAreaSize = NumGPRs * PtrByteSize;
+    unsigned AvailableFPRs = NumFPRs;
+    unsigned AvailableVRs = NumVRs;
+    unsigned NumBytesTmp = NumBytes;
+    for (unsigned i = 0; i != NumOps; ++i) {
+      if (Outs[i].Flags.isNest()) continue;
+      if (CalculateStackSlotUsed(Outs[i].VT, Outs[i].ArgVT, Outs[i].Flags,
+                                PtrByteSize, LinkageSize, ParamAreaSize,
+                                NumBytesTmp, AvailableFPRs, AvailableVRs,
+                                Subtarget.hasQPX()))
+        HasParameterArea = true;
+    }
+  }
+
   // When using the fast calling convention, we don't provide backing for
   // arguments that will be in registers.
   unsigned NumGPRsUsed = 0, NumFPRsUsed = 0, NumVRsUsed = 0;
@@ -5222,13 +5242,16 @@
 
   unsigned NumBytesActuallyUsed = NumBytes;
 
-  // The prolog code of the callee may store up to 8 GPR argument registers to
+  // In the old ELFv1 ABI, 
+  // the prolog code of the callee may store up to 8 GPR argument registers to
   // the stack, allowing va_start to index over them in memory if its varargs.
   // Because we cannot tell if this is needed on the caller side, we have to
   // conservatively assume that it is needed.  As such, make sure we have at
   // least enough stack space for the caller to store the 8 GPRs.
-  // FIXME: On ELFv2, it may be unnecessary to allocate the parameter area.
-  NumBytes = std::max(NumBytes, LinkageSize + 8 * PtrByteSize);
+  // In the ELFv2 ABI, we allocate the parameter area iff a callee 
+  // really requires memory operands, e.g. a vararg function.
+  if (HasParameterArea)
+    NumBytes = std::max(NumBytes, LinkageSize + 8 * PtrByteSize);
 
   // Tail call needs the stack to be aligned.
   if (getTargetMachine().Options.GuaranteedTailCallOpt &&