[AMDGPU][GlobalISel] Allow amdgpu_gfx calling conv

[sebastian-ne]

Summary

Calling functions from shaders already works with the SelectionDAG.

llvm/lib/Target/AMDGPU/AMDGPUCallLowering.cpp

bool AMDGPUCallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
   MachineFunction &MF = MIRBuilder.getMF();
   const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
   const SIRegisterInfo *TRI = ST.getRegisterInfo();
 
   const Function &F = MF.getFunction();
   MachineRegisterInfo &MRI = MF.getRegInfo();
   const SITargetLowering &TLI = *getTLI<SITargetLowering>();
   const DataLayout &DL = F.getParent()->getDataLayout();
-  CallingConv::ID CallConv = F.getCallingConv();
 
   if (!AMDGPUTargetMachine::EnableFixedFunctionABI &&
-      CallConv != CallingConv::AMDGPU_Gfx) {
+      Info.CallConv != CallingConv::AMDGPU_Gfx) {
     LLVM_DEBUG(dbgs() << "Variable function ABI not implemented\n");
     return false;
   }
 
-  if (AMDGPU::isShader(CallConv)) {
-    LLVM_DEBUG(dbgs() << "Unhandled call from graphics shader\n");
-    return false;
-  }
-
   SmallVector<ArgInfo, 8> OutArgs;
   for (auto &OrigArg : Info.OrigArgs)
     splitToValueTypes(OrigArg, OutArgs, DL, Info.CallConv);
 
   SmallVector<ArgInfo, 8> InArgs;
   if (Info.CanLowerReturn && !Info.OrigRet.Ty->isVoidTy())
     splitToValueTypes(Info.OrigRet, InArgs, DL, Info.CallConv);
 

llvm/test/CodeGen/AMDGPU/pal-simple-indirect-call.ll

 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; Check that no attributes are added to graphics functions
 ; RUN: opt -S -mtriple=amdgcn-amd-amdpal -amdgpu-annotate-kernel-features  %s | FileCheck -check-prefix=GCN %s
 
 ; Check that it doesn't crash
 ; RUN: llc -mtriple=amdgcn-amd-amdpal -mcpu=gfx900 < %s | FileCheck -check-prefixes=GFX9 %s
 ; RUN: llc -mtriple=amdgcn-amd-amdpal -mcpu=gfx1010 < %s | FileCheck -check-prefixes=GFX10 %s
+; RUN: llc -mtriple=amdgcn-amd-amdpal -mcpu=gfx1010 -global-isel < %s | FileCheck -check-prefixes=GFX10 %s
 
 target datalayout = "A5"
 
 define amdgpu_cs void @test_simple_indirect_call() {
 ; GCN-LABEL: define amdgpu_cs void @test_simple_indirect_call() {
 ; GFX9-LABEL: test_simple_indirect_call:
 ; GFX9:       ; %bb.0:
 ; GFX9-NEXT:    s_getpc_b64 s[36:37]