AMDGPU/SI: Prevent the DAGCombiner from creating setcc with i1 inputs

[• tstellarAMD]

Ping.

[arsenm]

lib/Target/AMDGPU/SIISelLowering.cpp

512–516

I think this should only do this for Op == ISD:SETCC.

We probably do want i1 logical operations to use the scalar 64-bit instructions on the results.

[• tstellarAMD]

Keep i1 as desirable for non-sett ops.

[• tstellarAMD]

Fix missing ampersand.

[arsenm]

LGTM

lib/Target/AMDGPU/SIISelLowering.h

EVT getOptimalMemOpType(uint64_t Size, unsigned DstAlign,
                           MachineFunction &MF) const override;
 
   TargetLoweringBase::LegalizeTypeAction
   getPreferredVectorAction(EVT VT) const override;
 
   bool shouldConvertConstantLoadToIntImm(const APInt &Imm,
                                         Type *Ty) const override;
 
+  bool isTypeDesirableForOp(unsigned Op, EVT VT) const override;
+
   SDValue LowerFormalArguments(SDValue Chain, CallingConv::ID CallConv,
                                bool isVarArg,
                                const SmallVectorImpl<ISD::InputArg> &Ins,
                                SDLoc DL, SelectionDAG &DAG,
                                SmallVectorImpl<SDValue> &InVals) const override;
 
   MachineBasicBlock * EmitInstrWithCustomInserter(MachineInstr * MI,
                                       MachineBasicBlock * BB) const override;

lib/Target/AMDGPU/SIISelLowering.cpp

 
 bool SITargetLowering::shouldConvertConstantLoadToIntImm(const APInt &Imm,
                                                          Type *Ty) const {
   const SIInstrInfo *TII =
       static_cast<const SIInstrInfo *>(Subtarget->getInstrInfo());
   return TII->isInlineConstant(Imm);
 }
 
+bool SITargetLowering::isTypeDesirableForOp(unsigned Op, EVT VT) const {
+
+  // SimplifySetCC uses this function to determine whether or not it should
+  // create setcc with i1 operands.  We don't want i1 setcc or really any i1
+  // operations.
+  if (VT == MVT::i1)
+    return false;
+
+  return TargetLowering::isTypeDesirableForOp(Op, VT);
+}
+
 SDValue SITargetLowering::LowerParameter(SelectionDAG &DAG, EVT VT, EVT MemVT,
                                          SDLoc SL, SDValue Chain,
                                          unsigned Offset, bool Signed) const {
   const DataLayout &DL = DAG.getDataLayout();
   MachineFunction &MF = DAG.getMachineFunction();
   const SIRegisterInfo *TRI =
       static_cast<const SIRegisterInfo*>(Subtarget->getRegisterInfo());
   unsigned InputPtrReg = TRI->getPreloadedValue(MF, SIRegisterInfo::INPUT_PTR);

test/CodeGen/AMDGPU/setcc.ll

define void @v3i8_eq(<3 x i8> addrspace(1)* %out, <3 x i8> addrspace(1)* %ptra, <3 x i8> addrspace(1)* %ptrb) {
   %gep.out = getelementptr <3 x i8>, <3 x i8> addrspace(1)* %out, i32 %tid
   %a = load <3 x i8>, <3 x i8> addrspace(1)* %gep.a
   %b = load <3 x i8>, <3 x i8> addrspace(1)* %gep.b
   %cmp = icmp eq <3 x i8> %a, %b
   %ext = sext <3 x i1> %cmp to <3 x i8>
   store <3 x i8> %ext, <3 x i8> addrspace(1)* %gep.out
   ret void
 }
+
+; Make sure we don't try to emit i1 setcc ops
+; FUNC-LABEL: setcc-i1
+; SI: s_and_b32 [[AND:s[0-9]+]], s{{[0-9]+}}, 1
+; SI: v_cmp_eq_i32_e64 s[0:1], 0, [[AND]]
+define void @setcc-i1(i32 %in) {
+  %and = and i32 %in, 1
+  %cmp = icmp eq i32 %and, 0
+  br i1 %cmp, label %endif, label %if
+if:
+  unreachable
+endif:
+  ret void
+}

test/CodeGen/AMDGPU/trunc-cmp-constant.ll

 ; RUN: llc -march=amdgcn -mcpu=SI -verify-machineinstrs < %s | FileCheck -check-prefix=SI -check-prefix=FUNC %s
 ; RUN: llc -march=amdgcn -mcpu=tonga -verify-machineinstrs < %s | FileCheck -check-prefix=SI -check-prefix=FUNC %s
 
 ; FUNC-LABEL {{^}}sextload_i1_to_i32_trunc_cmp_eq_0:
 ; SI: buffer_load_ubyte [[LOAD:v[0-9]+]]
 ; SI: v_and_b32_e32 [[TMP:v[0-9]+]], 1, [[LOAD]]
-; SI: v_cmp_eq_i32_e32 vcc, 1, [[TMP]]{{$}}
-; SI: s_xor_b64 s{{\[[0-9]+:[0-9]+\]}}, vcc, -1{{$}}
+; SI: v_cmp_eq_i32_e32 vcc, 0, [[TMP]]{{$}}
 ; SI: v_cndmask_b32_e64
 ; SI: buffer_store_byte
 define void @sextload_i1_to_i32_trunc_cmp_eq_0(i1 addrspace(1)* %out, i1 addrspace(1)* %in) nounwind {
   %load = load i1, i1 addrspace(1)* %in
   %ext = sext i1 %load to i32
   %cmp = icmp eq i32 %ext, 0
   store i1 %cmp, i1 addrspace(1)* %out
   ret void