AMDGPU/GlobalISel: Implement call lowering for shaders returning values

Reviewers: arsenm, nhaehnle

Subscribers: kzhuravl, jvesely, wdng, yaxunl, rovka, kristof.beyls, dstuttard, tpr, t-tye, volkan, llvm-commits

Differential Revision: https://reviews.llvm.org/D57166

llvm-svn: 357964

llvm/lib/Target/AMDGPU/AMDGPUCallLowering.cpp

@@ -20,12 +20,49 @@
 #include "SIMachineFunctionInfo.h"
 #include "SIRegisterInfo.h"
 #include "MCTargetDesc/AMDGPUMCTargetDesc.h"
+#include "llvm/CodeGen/Analysis.h"
 #include "llvm/CodeGen/CallingConvLower.h"
 #include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/Support/LowLevelTypeImpl.h"
 
 using namespace llvm;
 
+namespace {
+
+struct OutgoingArgHandler : public CallLowering::ValueHandler {
+  OutgoingArgHandler(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI,
+                     MachineInstrBuilder MIB, CCAssignFn *AssignFn)
+      : ValueHandler(MIRBuilder, MRI, AssignFn), MIB(MIB) {}
+
+  MachineInstrBuilder MIB;
+
+  unsigned getStackAddress(uint64_t Size, int64_t Offset,
+                           MachinePointerInfo &MPO) override {
+    llvm_unreachable("not implemented");
+  }
+
+  void assignValueToAddress(unsigned ValVReg, unsigned Addr, uint64_t Size,
+                            MachinePointerInfo &MPO, CCValAssign &VA) override {
+    llvm_unreachable("not implemented");
+  }
+
+  void assignValueToReg(unsigned ValVReg, unsigned PhysReg,
+                        CCValAssign &VA) override {
+    MIB.addUse(PhysReg);
+    MIRBuilder.buildCopy(PhysReg, ValVReg);
+  }
+
+  bool assignArg(unsigned ValNo, MVT ValVT, MVT LocVT,
+                 CCValAssign::LocInfo LocInfo,
+                 const CallLowering::ArgInfo &Info,
+                 CCState &State) override {
+    return AssignFn(ValNo, ValVT, LocVT, LocInfo, Info.Flags, State);
+  }
+};
+
+}
+
 AMDGPUCallLowering::AMDGPUCallLowering(const AMDGPUTargetLowering &TLI)
   : CallLowering(&TLI) {
 }
@@ -33,11 +70,44 @@ AMDGPUCallLowering::AMDGPUCallLowering(const AMDGPUTargetLowering &TLI)
 bool AMDGPUCallLowering::lowerReturn(MachineIRBuilder &MIRBuilder,
                                      const Value *Val,
                                      ArrayRef<unsigned> VRegs) const {
-  // FIXME: Add support for non-void returns.
-  if (Val)
+
+  MachineFunction &MF = MIRBuilder.getMF();
+  MachineRegisterInfo &MRI = MF.getRegInfo();
+  SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
+  MFI->setIfReturnsVoid(!Val);
+
+  if (!Val) {
+    MIRBuilder.buildInstr(AMDGPU::S_ENDPGM).addImm(0);
+    return true;
+  }
+
+  unsigned VReg = VRegs[0];
+
+  const Function &F = MF.getFunction();
+  auto &DL = F.getParent()->getDataLayout();
+  if (!AMDGPU::isShader(F.getCallingConv()))
     return false;
 
-  MIRBuilder.buildInstr(AMDGPU::S_ENDPGM).addImm(0);
+
+  const AMDGPUTargetLowering &TLI = *getTLI<AMDGPUTargetLowering>();
+  SmallVector<EVT, 4> SplitVTs;
+  SmallVector<uint64_t, 4> Offsets;
+  ArgInfo OrigArg{VReg, Val->getType()};
+  setArgFlags(OrigArg, AttributeList::ReturnIndex, DL, F);
+  ComputeValueVTs(TLI, DL, OrigArg.Ty, SplitVTs, &Offsets, 0);
+
+  SmallVector<ArgInfo, 8> SplitArgs;
+  CCAssignFn *AssignFn = CCAssignFnForReturn(F.getCallingConv(), false);
+  for (unsigned i = 0, e = Offsets.size(); i != e; ++i) {
+    Type *SplitTy = SplitVTs[i].getTypeForEVT(F.getContext());
+    SplitArgs.push_back({VRegs[i], SplitTy, OrigArg.Flags, OrigArg.IsFixed});
+  }
+  auto RetInstr = MIRBuilder.buildInstrNoInsert(AMDGPU::SI_RETURN_TO_EPILOG);
+  OutgoingArgHandler Handler(MIRBuilder, MRI, RetInstr, AssignFn);
+  if (!handleAssignments(MIRBuilder, SplitArgs, Handler))
+    return false;
+  MIRBuilder.insertInstr(RetInstr);
+
   return true;
 }
 

llvm/test/CodeGen/AMDGPU/GlobalISel/irtranslator-amdgpu_vs.ll

@@ -55,6 +55,27 @@ define amdgpu_vs void @test_order(float inreg %arg0, float inreg %arg1, float %a
   ret void
 }
 
+; CHECK-LABEL: name: ret_struct
+; CHECK: [[S0:%[0-9]+]]:_(s32) = COPY $sgpr0
+; CHECK: [[S1:%[0-9]+]]:_(s32) = COPY $sgpr1
+; CHECK: $sgpr0 = COPY [[S0]]
+; CHECK: $sgpr1 = COPY [[S1]]
+; CHECK: SI_RETURN_TO_EPILOG $sgpr0, $sgpr1
+define amdgpu_vs <{ i32, i32 }> @ret_struct(i32 inreg %arg0, i32 inreg %arg1) {
+main_body:
+  %tmp0 = insertvalue <{ i32, i32 }> undef, i32 %arg0, 0
+  %tmp1 = insertvalue <{ i32, i32 }> %tmp0, i32 %arg1, 1
+  ret <{ i32, i32 }> %tmp1
+}
+
+; CHECK_LABEL: name: non_void_ret
+; CHECK: [[ZERO:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
+; CHECK: $sgpr0 = COPY [[ZERO]]
+; SI_RETURN_TO_EPILOG $sgpr0
+define amdgpu_vs i32 @non_void_ret() {
+  ret i32 0
+}
+
 declare void @llvm.amdgcn.exp.f32(i32, i32, float, float, float, float, i1, i1)  #0
 
 attributes #0 = { nounwind }

llvm/test/CodeGen/AMDGPU/GlobalISel/todo.ll

@@ -1,10 +0,0 @@
-; RUN: llc -mtriple=amdgcn-mesa-mesa3d -global-isel -global-isel-abort=2 %s -o - 2>&1 | FileCheck %s
-
-; This isn't implemented, but we need to make sure we fall back to SelectionDAG
-; instead of generating wrong code.
-; CHECK: warning: Instruction selection used fallback path for non_void_ret
-; CHECK: non_void_ret:
-; CHECK-NOT: s_endpgm
-define amdgpu_vs i32 @non_void_ret() {
-  ret i32 0
-}