AMDGPU/SI: Add support for non-void functions

Summary:
Return values can be stored in SGPRs (i32) and VGPRs (f32).

This will be used by functions which expect some bytecode or other binary to
be appended at the end. It allows defining in which registers the return
values will be stored.

v2: don't do this for compute shaders

Reviewers: tstellarAMD, arsenm

Subscribers: arsenm

Differential Revision: http://reviews.llvm.org/D16033

llvm-svn: 257621

6 files changed, 136 insertions, 1 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUCallingConv.td b/llvm/lib/Target/AMDGPU/AMDGPUCallingConv.td
index 36ed1ed1295..b0db26124a0 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUCallingConv.td
+++ b/llvm/lib/Target/AMDGPU/AMDGPUCallingConv.td
@@ -66,6 +66,37 @@ def CC_SI : CallingConv<[
 
 ]>;
 
+def RetCC_SI : CallingConv<[
+  CCIfType<[i32] , CCAssignToReg<[
+    SGPR0, SGPR1, SGPR2, SGPR3, SGPR4, SGPR5, SGPR6, SGPR7,
+    SGPR8, SGPR9, SGPR10, SGPR11, SGPR12, SGPR13, SGPR14, SGPR15,
+    SGPR16, SGPR17, SGPR18, SGPR19, SGPR20, SGPR21, SGPR22, SGPR23,
+    SGPR24, SGPR25, SGPR26, SGPR27, SGPR28, SGPR29, SGPR30, SGPR31,
+    SGPR32, SGPR33, SGPR34, SGPR35, SGPR36, SGPR37, SGPR38, SGPR39
+  ]>>,
+
+  // 32*4 + 4 is the minimum for a fetch shader with 32 outputs.
+  CCIfType<[f32] , CCAssignToReg<[
+    VGPR0, VGPR1, VGPR2, VGPR3, VGPR4, VGPR5, VGPR6, VGPR7,
+    VGPR8, VGPR9, VGPR10, VGPR11, VGPR12, VGPR13, VGPR14, VGPR15,
+    VGPR16, VGPR17, VGPR18, VGPR19, VGPR20, VGPR21, VGPR22, VGPR23,
+    VGPR24, VGPR25, VGPR26, VGPR27, VGPR28, VGPR29, VGPR30, VGPR31,
+    VGPR32, VGPR33, VGPR34, VGPR35, VGPR36, VGPR37, VGPR38, VGPR39,
+    VGPR40, VGPR41, VGPR42, VGPR43, VGPR44, VGPR45, VGPR46, VGPR47,
+    VGPR48, VGPR49, VGPR50, VGPR51, VGPR52, VGPR53, VGPR54, VGPR55,
+    VGPR56, VGPR57, VGPR58, VGPR59, VGPR60, VGPR61, VGPR62, VGPR63,
+    VGPR64, VGPR65, VGPR66, VGPR67, VGPR68, VGPR69, VGPR70, VGPR71,
+    VGPR72, VGPR73, VGPR74, VGPR75, VGPR76, VGPR77, VGPR78, VGPR79,
+    VGPR80, VGPR81, VGPR82, VGPR83, VGPR84, VGPR85, VGPR86, VGPR87,
+    VGPR88, VGPR89, VGPR90, VGPR91, VGPR92, VGPR93, VGPR94, VGPR95,
+    VGPR96, VGPR97, VGPR98, VGPR99, VGPR100, VGPR101, VGPR102, VGPR103,
+    VGPR104, VGPR105, VGPR106, VGPR107, VGPR108, VGPR109, VGPR110, VGPR111,
+    VGPR112, VGPR113, VGPR114, VGPR115, VGPR116, VGPR117, VGPR118, VGPR119,
+    VGPR120, VGPR121, VGPR122, VGPR123, VGPR124, VGPR125, VGPR126, VGPR127,
+    VGPR128, VGPR129, VGPR130, VGPR131, VGPR132, VGPR133, VGPR134, VGPR135
+  ]>>
+]>;
+
 // Calling convention for R600
 def CC_R600 : CallingConv<[
   CCIfInReg<CCIfType<[v4f32, v4i32] , CCAssignToReg<[
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp b/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
index 2b8032e38a5..1a59a460ee7 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
@@ -572,6 +572,12 @@ void AMDGPUTargetLowering::AnalyzeFormalArguments(CCState &State,
   State.AnalyzeFormalArguments(Ins, CC_AMDGPU);
 }
 
+void AMDGPUTargetLowering::AnalyzeReturn(CCState &State,
+                           const SmallVectorImpl<ISD::OutputArg> &Outs) const {
+
+  State.AnalyzeReturn(Outs, RetCC_SI);
+}
+
 SDValue AMDGPUTargetLowering::LowerReturn(
                                      SDValue Chain,
                                      CallingConv::ID CallConv,
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.h b/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.h
index 65e4a0a7186..37925416a9c 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.h
+++ b/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.h
@@ -115,6 +115,8 @@ protected:
                                SmallVectorImpl<ISD::InputArg> &OrigIns) const;
   void AnalyzeFormalArguments(CCState &State,
                               const SmallVectorImpl<ISD::InputArg> &Ins) const;
+  void AnalyzeReturn(CCState &State,
+                     const SmallVectorImpl<ISD::OutputArg> &Outs) const;
 
 public:
   AMDGPUTargetLowering(TargetMachine &TM, const AMDGPUSubtarget &STI);
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUInstrInfo.td b/llvm/lib/Target/AMDGPU/AMDGPUInstrInfo.td
index b7a263e34e7..575dfe41365 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUInstrInfo.td
+++ b/llvm/lib/Target/AMDGPU/AMDGPUInstrInfo.td
@@ -242,4 +242,4 @@ def IL_brcond      : SDNode<"AMDGPUISD::BRANCH_COND", SDTIL_BRCond, [SDNPHasChai
 // Call/Return DAG Nodes
 //===----------------------------------------------------------------------===//
 def IL_retflag       : SDNode<"AMDGPUISD::RET_FLAG", SDTNone,
-    [SDNPHasChain, SDNPOptInGlue]>;
+    [SDNPHasChain, SDNPOptInGlue, SDNPVariadic]>;
diff --git a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
index 6ba61b28ba2..0c678c4b73b 100644
--- a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
@@ -880,6 +880,95 @@ SDValue SITargetLowering::LowerFormalArguments(
   return DAG.getNode(ISD::TokenFactor, DL, MVT::Other, Chains);
 }
 
+SDValue SITargetLowering::LowerReturn(SDValue Chain,
+                                      CallingConv::ID CallConv,
+                                      bool isVarArg,
+                                      const SmallVectorImpl<ISD::OutputArg> &Outs,
+                                      const SmallVectorImpl<SDValue> &OutVals,
+                                      SDLoc DL, SelectionDAG &DAG) const {
+  MachineFunction &MF = DAG.getMachineFunction();
+  SIMachineFunctionInfo *Info = MF.getInfo<SIMachineFunctionInfo>();
+
+  if (Info->getShaderType() == ShaderType::COMPUTE)
+    return AMDGPUTargetLowering::LowerReturn(Chain, CallConv, isVarArg, Outs,
+                                             OutVals, DL, DAG);
+
+  SmallVector<ISD::OutputArg, 48> Splits;
+  SmallVector<SDValue, 48> SplitVals;
+
+  // Split vectors into their elements.
+  for (unsigned i = 0, e = Outs.size(); i != e; ++i) {
+    const ISD::OutputArg &Out = Outs[i];
+
+    if (Out.VT.isVector()) {
+      MVT VT = Out.VT.getVectorElementType();
+      ISD::OutputArg NewOut = Out;
+      NewOut.Flags.setSplit();
+      NewOut.VT = VT;
+
+      // We want the original number of vector elements here, e.g.
+      // three or five, not four or eight.
+      unsigned NumElements = Out.ArgVT.getVectorNumElements();
+
+      for (unsigned j = 0; j != NumElements; ++j) {
+        SDValue Elem = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, DL, VT, OutVals[i],
+                                   DAG.getConstant(j, DL, MVT::i32));
+        SplitVals.push_back(Elem);
+        Splits.push_back(NewOut);
+        NewOut.PartOffset += NewOut.VT.getStoreSize();
+      }
+    } else {
+      SplitVals.push_back(OutVals[i]);
+      Splits.push_back(Out);
+    }
+  }
+
+  // CCValAssign - represent the assignment of the return value to a location.
+  SmallVector<CCValAssign, 48> RVLocs;
+
+  // CCState - Info about the registers and stack slots.
+  CCState CCInfo(CallConv, isVarArg, DAG.getMachineFunction(), RVLocs,
+                 *DAG.getContext());
+
+  // Analyze outgoing return values.
+  AnalyzeReturn(CCInfo, Splits);
+
+  SDValue Flag;
+  SmallVector<SDValue, 48> RetOps;
+  RetOps.push_back(Chain); // Operand #0 = Chain (updated below)
+
+  // Copy the result values into the output registers.
+  for (unsigned i = 0, realRVLocIdx = 0;
+       i != RVLocs.size();
+       ++i, ++realRVLocIdx) {
+    CCValAssign &VA = RVLocs[i];
+    assert(VA.isRegLoc() && "Can only return in registers!");
+
+    SDValue Arg = SplitVals[realRVLocIdx];
+
+    // Copied from other backends.
+    switch (VA.getLocInfo()) {
+    default: llvm_unreachable("Unknown loc info!");
+    case CCValAssign::Full:
+      break;
+    case CCValAssign::BCvt:
+      Arg = DAG.getNode(ISD::BITCAST, DL, VA.getLocVT(), Arg);
+      break;
+    }
+
+    Chain = DAG.getCopyToReg(Chain, DL, VA.getLocReg(), Arg, Flag);
+    Flag = Chain.getValue(1);
+    RetOps.push_back(DAG.getRegister(VA.getLocReg(), VA.getLocVT()));
+  }
+
+  // Update chain and glue.
+  RetOps[0] = Chain;
+  if (Flag.getNode())
+    RetOps.push_back(Flag);
+
+  return DAG.getNode(AMDGPUISD::RET_FLAG, DL, MVT::Other, RetOps);
+}
+
 MachineBasicBlock * SITargetLowering::EmitInstrWithCustomInserter(
     MachineInstr * MI, MachineBasicBlock * BB) const {
 
diff --git a/llvm/lib/Target/AMDGPU/SIISelLowering.h b/llvm/lib/Target/AMDGPU/SIISelLowering.h
index e2f8cb19d6b..f01b2c0d09f 100644
--- a/llvm/lib/Target/AMDGPU/SIISelLowering.h
+++ b/llvm/lib/Target/AMDGPU/SIISelLowering.h
@@ -95,6 +95,13 @@ public:
                                SDLoc DL, SelectionDAG &DAG,
                                SmallVectorImpl<SDValue> &InVals) const override;
 
+  SDValue LowerReturn(SDValue Chain,
+                      CallingConv::ID CallConv,
+                      bool isVarArg,
+                      const SmallVectorImpl<ISD::OutputArg> &Outs,
+                      const SmallVectorImpl<SDValue> &OutVals,
+                      SDLoc DL, SelectionDAG &DAG) const override;
+
   MachineBasicBlock * EmitInstrWithCustomInserter(MachineInstr * MI,
                                       MachineBasicBlock * BB) const override;
   bool enableAggressiveFMAFusion(EVT VT) const override;