[AMDGPU] New intrinsic void llvm.amdgcn.s.nop(i16) (#65757)

This allows front ends to insert s_nops - this is most often when a
delay less
than s_sleep 1 is required.

Author: dstutt

llvm/include/llvm/IR/IntrinsicsAMDGPU.td

@@ -1677,6 +1677,11 @@ def int_amdgcn_s_sleep :
                                 IntrHasSideEffects]> {
 }
 
+def int_amdgcn_s_nop :
+  DefaultAttrsIntrinsic<[], [llvm_i16_ty], [ImmArg<ArgIndex<0>>, IntrNoMem,
+                                IntrHasSideEffects]> {
+}
+
 def int_amdgcn_s_incperflevel :
   ClangBuiltin<"__builtin_amdgcn_s_incperflevel">,
   DefaultAttrsIntrinsic<[], [llvm_i32_ty], [ImmArg<ArgIndex<0>>, IntrNoMem,

llvm/lib/Target/AMDGPU/SOPInstructions.td

@@ -1161,7 +1161,8 @@ multiclass SOPP_With_Relaxation <string opName, dag ins,
   def _pad_s_nop : SOPP_Pseudo <opName # "_pad_s_nop", ins, asmOps, pattern, " ", opName>;
 }
 
-def S_NOP : SOPP_Pseudo<"s_nop" , (ins i16imm:$simm16), "$simm16"> {
+def S_NOP : SOPP_Pseudo<"s_nop" , (ins i16imm:$simm16), "$simm16",
+  [(int_amdgcn_s_nop timm:$simm16)]> {
   let hasSideEffects = 1;
 }
 

llvm/test/CodeGen/AMDGPU/llvm.amdgcn.s.nop.ll

@@ -0,0 +1,30 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -march=amdgcn -mcpu=gfx900 -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
+; RUN: llc -global-isel -march=amdgcn -mcpu=gfx900 -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
+
+define amdgpu_kernel void @test_s_nop() {
+; GCN-LABEL: test_s_nop:
+; GCN:       ; %bb.0:
+; GCN-NEXT:    s_nop 0
+; GCN-NEXT:    s_nop 1
+; GCN-NEXT:    s_nop 2
+; GCN-NEXT:    s_nop 3
+; GCN-NEXT:    s_nop 4
+; GCN-NEXT:    s_nop 5
+; GCN-NEXT:    s_nop 6
+; GCN-NEXT:    s_nop 7
+; GCN-NEXT:    s_nop 63
+; GCN-NEXT:    s_endpgm
+  call void @llvm.amdgcn.s.nop(i16 0)
+  call void @llvm.amdgcn.s.nop(i16 1)
+  call void @llvm.amdgcn.s.nop(i16 2)
+  call void @llvm.amdgcn.s.nop(i16 3)
+  call void @llvm.amdgcn.s.nop(i16 4)
+  call void @llvm.amdgcn.s.nop(i16 5)
+  call void @llvm.amdgcn.s.nop(i16 6)
+  call void @llvm.amdgcn.s.nop(i16 7)
+  call void @llvm.amdgcn.s.nop(i16 63)
+  ret void
+}
+
+declare void @llvm.amdgcn.s.nop(i16)