[Backport to 20] Partial pick of #3106 - Set an arg of __spirv_ocl_nan to unsigned

OpenCL built-in nan's argument type is unsigned.

Author: wenju-he

lib/SPIRV/SPIRVUtil.cpp

@@ -2650,6 +2650,9 @@ class OpenCLStdToSPIRVFriendlyIRMangleInfo : public BuiltinFuncMangleInfo {
     case OpenCLLIB::S_Upsample:
       addUnsignedArg(1);
       break;
+    case OpenCLLIB::Nan:
+      addUnsignedArg(0);
+      break;
     case OpenCLLIB::Vloadn:
     case OpenCLLIB::Vload_half:
     case OpenCLLIB::Vload_halfn:

test/transcoding/OpenCL/nan.ll

@@ -0,0 +1,33 @@
+; RUN: llvm-as %s -o %t.bc
+; RUN: llvm-spirv %t.bc -o %t.spv
+; RUN: llvm-spirv %t.spv -to-text -o %t.spt
+; RUN: FileCheck < %t.spt %s --check-prefix=CHECK-SPIRV
+
+; RUN: llvm-spirv -r %t.spv -o %t.rev.bc
+; RUN: llvm-dis < %t.rev.bc | FileCheck %s --check-prefixes=CHECK-LLVM
+; RUN: llvm-spirv -r %t.spv --spirv-target-env=SPV-IR -o %t.rev.bc
+; RUN: llvm-dis < %t.rev.bc | FileCheck %s --check-prefixes=CHECK-SPV-IR
+
+; Check OpenCL built-in nan translation.
+
+target datalayout = "e-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-n8:16:32:64-G1"
+target triple = "spir64"
+
+; CHECK-SPIRV: ExtInst [[#]] [[#]] [[#]] nan
+
+; CHECK-LLVM: call spir_func float @_Z3nanj(
+
+; CHECK-SPV-IR: call spir_func float @_Z15__spirv_ocl_nanj(
+
+define dso_local spir_kernel void @test(ptr addrspace(1) align 4 %a, i32 %b) {
+entry:
+  %call = tail call spir_func float @_Z3nanj(i32 %b)
+  store float %call, ptr addrspace(1) %a, align 4
+  ret void
+}
+
+declare spir_func float @_Z3nanj(i32)
+
+!opencl.ocl.version = !{!0}
+
+!0 = !{i32 3, i32 0}