AMDGPU/SI: Add llvm.amdgcn.v.interp.p[12] intrinsics

[• tstellarAMD]

Summary

These are meant to be used instead of the llvm.SI.fs.interp intrinsic which
will be deprecated at some point.

[arsenm]

include/llvm/IR/IntrinsicsAMDGPU.td

135

I'm not sure this should have the v prefix

lib/Target/AMDGPU/AMDGPUIntrinsicExpander.cpp

1 ↗

(On Diff #42621)

Why is this easier than handling the differences during intrinsic lowering?

test/CodeGen/AMDGPU/llvm.SI.fs.interp.ll

74–78 ↗

(On Diff #42621)

Should be moved into file with new name

[• tstellarAMD]

lib/Target/AMDGPU/AMDGPUIntrinsicExpander.cpp

1 ↗

(On Diff #42621)

I would like to stop using the intrinsics like fs.interp which are more like library calls, so I don't want to add them to the public IntrinsicsAMDGPU.td file. Having an IR expansion pass here means I only need to handle the lower-level intrinsics in isSourceOfDivergence(), and I don't need to use AMGPUInstrinsicInfo to look up intrinsic names.

[• tstellarAMD]

Keep old intrinsic and drop AMDGPUIntrinsicExpander pass

[arsenm]

LGTM

include/llvm/IR/IntrinsicsAMDGPU.td

 def int_amdgcn_s_dcache_wb_vol :
   GCCBuiltin<"__builtin_amdgcn_s_dcache_wb_vol">,
   Intrinsic<[], [], []>;
 
 def int_amdgcn_dispatch_ptr :
   GCCBuiltin<"__builtin_amdgcn_dispatch_ptr">,
   Intrinsic<[LLVMQualPointerType<llvm_i8_ty, 2>], [], [IntrNoMem]>;
 
+// __builtin_amdgcn_interp_p1 <i>, <attr_chan>, <attr>, <m0>
+def int_amdgcn_interp_p1 :
+  GCCBuiltin<"__builtin_amdgcn_interp_p1">,
+  Intrinsic<[llvm_float_ty],
+            [llvm_i32_ty, llvm_i32_ty, llvm_i32_ty, llvm_i32_ty],
+            [IntrNoMem]>;  // This intrinsic reads from lds, but the memory
+                           // values are constant, so it behaves like IntrNoMem.
+
+// __builtin_amdgcn_interp_p2 <p1>, <j>, <attr_chan>, <attr>, <m0>
+def int_amdgcn_interp_p2 :
+  GCCBuiltin<"__builtin_amdgcn_interp_p2">,
+  Intrinsic<[llvm_float_ty],
+            [llvm_float_ty, llvm_i32_ty, llvm_i32_ty, llvm_i32_ty, llvm_i32_ty],
+            [IntrNoMem]>;  // See int_amdgcn_v_interp_p1 for why this is
+                           // IntrNoMem.
 }

lib/Target/AMDGPU/SIISelLowering.cpp

case AMDGPUIntrinsic::SI_fs_interp: {
     SDValue Glue = M0.getValue(1);
     SDValue P1 = DAG.getNode(AMDGPUISD::INTERP_P1, DL,
                              DAG.getVTList(MVT::f32, MVT::Glue),
                              I, Op.getOperand(1), Op.getOperand(2), Glue);
     Glue = SDValue(P1.getNode(), 1);
     return DAG.getNode(AMDGPUISD::INTERP_P2, DL, MVT::f32, P1, J,
                              Op.getOperand(1), Op.getOperand(2), Glue);
   }
+  case Intrinsic::amdgcn_interp_p1: {
+    SDValue M0 = copyToM0(DAG, DAG.getEntryNode(), DL, Op.getOperand(4));
+    SDValue Glue = M0.getValue(1);
+    return DAG.getNode(AMDGPUISD::INTERP_P1, DL, MVT::f32, Op.getOperand(1),
+                       Op.getOperand(2), Op.getOperand(3), Glue);
+  }
+  case Intrinsic::amdgcn_interp_p2: {
+    SDValue M0 = copyToM0(DAG, DAG.getEntryNode(), DL, Op.getOperand(5));
+    SDValue Glue = SDValue(M0.getNode(), 1);
+    return DAG.getNode(AMDGPUISD::INTERP_P2, DL, MVT::f32, Op.getOperand(1),
+                       Op.getOperand(2), Op.getOperand(3), Op.getOperand(4),
+                       Glue);
+  }
   default:
     return AMDGPUTargetLowering::LowerOperation(Op, DAG);
   }
 }
 
 SDValue SITargetLowering::LowerINTRINSIC_VOID(SDValue Op,
                                               SelectionDAG &DAG) const {
   MachineFunction &MF = DAG.getMachineFunction();

test/CodeGen/AMDGPU/llvm.amdgcn.interp.ll

+;RUN: llc < %s -march=amdgcn -mcpu=verde -verify-machineinstrs | FileCheck --check-prefix=GCN %s
+;RUN: llc < %s -march=amdgcn -mcpu=tonga -verify-machineinstrs | FileCheck --check-prefix=GCN %s
+
+;GCN-LABEL: {{^}}v_interp:
+;GCN-NOT: s_wqm
+;GCN: s_mov_b32 m0, s{{[0-9]+}}
+;GCN: v_interp_p1_f32
+;GCN: v_interp_p2_f32
+define void @v_interp(<16 x i8> addrspace(2)* inreg, <16 x i8> addrspace(2)* inreg, <32 x i8> addrspace(2)* inreg, i32 inreg, <2 x i32>) #0 {
+main_body:
+  %i = extractelement <2 x i32> %4, i32 0
+  %j = extractelement <2 x i32> %4, i32 1
+  %p0_0 = call float @llvm.amdgcn.interp.p1(i32 %i, i32 0, i32 0, i32 %3)
+  %p1_0 = call float @llvm.amdgcn.interp.p2(float %p0_0, i32 %j, i32 0, i32 0, i32 %3)
+  %p0_1 = call float @llvm.amdgcn.interp.p1(i32 %i, i32 1, i32 0, i32 %3)
+  %p1_1 = call float @llvm.amdgcn.interp.p2(float %p0_1, i32 %j, i32 1, i32 0, i32 %3)
+  call void @llvm.SI.export(i32 15, i32 1, i32 1, i32 0, i32 1, float %p0_0, float %p0_0, float %p1_1, float %p1_1)
+  ret void
+}
+
+; Function Attrs: nounwind readnone
+declare float @llvm.amdgcn.interp.p1(i32, i32, i32, i32) #1
+
+; Function Attrs: nounwind readnone
+declare float @llvm.amdgcn.interp.p2(float, i32, i32, i32, i32) #1
+
+declare void @llvm.SI.export(i32, i32, i32, i32, i32, float, float, float, float)
+
+attributes #0 = { "ShaderType"="0" }
+attributes #1 = { nounwind readnone }