[AMDGPU] calling conventions for AMDPAL OS type

Summary:
This commit adds comments on how the AMDPAL OS type overloads the
existing AMDGPU_ calling conventions used by Mesa, and adds a couple of
new ones.

Reviewers: arsenm, nhaehnle, dstuttard

Subscribers: mehdi_amini, kzhuravl, wdng, yaxunl, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D37752

llvm-svn: 314502
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUTargetTransformInfo.cpp b/llvm/lib/Target/AMDGPU/AMDGPUTargetTransformInfo.cpp
index d607fc5..153a4a8 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUTargetTransformInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUTargetTransformInfo.cpp
@@ -491,7 +491,9 @@
   case CallingConv::SPIR_KERNEL:
     return true;
   case CallingConv::AMDGPU_VS:
+  case CallingConv::AMDGPU_LS:
   case CallingConv::AMDGPU_HS:
+  case CallingConv::AMDGPU_ES:
   case CallingConv::AMDGPU_GS:
   case CallingConv::AMDGPU_PS:
   case CallingConv::AMDGPU_CS: