[AMDGPU] ISel for llvm.amdgcn.set.inactive.chain.arg

Add patterns to select int_amdgcn_set_inactive_chain_arg to
V_SET_INACTIVE.

This could probably use some more testing, but at least for simple cases
V_SET_INACTIVE seems to mostly work out of the box.

Differential Revision: https://reviews.llvm.org/D158605

Author: rovka

llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp

@@ -4309,6 +4309,7 @@ AMDGPURegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
     case Intrinsic::amdgcn_wqm:
     case Intrinsic::amdgcn_softwqm:
     case Intrinsic::amdgcn_set_inactive:
+    case Intrinsic::amdgcn_set_inactive_chain_arg:
     case Intrinsic::amdgcn_permlane64:
       return getDefaultMappingAllVGPR(MI);
     case Intrinsic::amdgcn_cvt_pkrtz:

llvm/lib/Target/AMDGPU/SIInstructions.td

@@ -259,6 +259,12 @@ def V_SET_INACTIVE_B64 : VPseudoInstSI <(outs VReg_64:$vdst),
 }
 } // End Defs = [SCC]
 
+def : GCNPat<(i32 (int_amdgcn_set_inactive_chain_arg i32:$src, i32:$inactive)),
+    (V_SET_INACTIVE_B32 VGPR_32:$src, VGPR_32:$inactive)>;
+
+def : GCNPat<(i64 (int_amdgcn_set_inactive_chain_arg i64:$src, i64:$inactive)),
+    (V_SET_INACTIVE_B64 VReg_64:$src, VReg_64:$inactive)>;
+
 let usesCustomInserter = 1, hasSideEffects = 0, mayLoad = 0, mayStore = 0, Uses = [EXEC] in {
   def WAVE_REDUCE_UMIN_PSEUDO_U32 : VPseudoInstSI <(outs SGPR_32:$sdst),
     (ins VSrc_b32: $src, VSrc_b32:$strategy),