[mlir:LLVM] Fix minor bug, missing cconv translation

[hgreving]

Summary

Fixes translating the calling convention to LLVM-IR, possibly missed
by https://reviews.llvm.org/D126161, and adds a test.

[hgreving]

Committed at 37c750a5fd13 (forgot to mark in the commit message).

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

LogicalResult ModuleTranslation::convertFunctionSignatures() {
   // Declare all functions first because there may be function calls that form a
   // call graph with cycles, or global initializers that reference functions.
   for (auto function : getModuleBody(mlirModule).getOps<LLVMFuncOp>()) {
     llvm::FunctionCallee llvmFuncCst = llvmModule->getOrInsertFunction(
         function.getName(),
         cast<llvm::FunctionType>(convertType(function.getFunctionType())));
     llvm::Function *llvmFunc = cast<llvm::Function>(llvmFuncCst.getCallee());
     llvmFunc->setLinkage(convertLinkageToLLVM(function.getLinkage()));
+    llvmFunc->setCallingConv(convertCConvToLLVM(function.getCConv()));
     mapFunction(function.getName(), llvmFunc);
     addRuntimePreemptionSpecifier(function.getDsoLocal(), llvmFunc);
 
     // Convert function attributes.
     if (function->getAttrOfType<UnitAttr>(LLVMDialect::getReadnoneAttrName()))
       llvmFunc->setDoesNotAccessMemory();
 
     // Convert function_entry_count attribute to metadata.

mlir/test/Dialect/LLVMIR/func.mlir

 // RUN: mlir-opt -split-input-file -verify-diagnostics %s | mlir-opt | FileCheck %s
 // RUN: mlir-opt -split-input-file -verify-diagnostics -mlir-print-op-generic %s | FileCheck %s --check-prefix=GENERIC
 // RUN: mlir-opt -split-input-file -verify-diagnostics %s -mlir-print-debuginfo | mlir-opt -mlir-print-debuginfo | FileCheck %s --check-prefix=LOCINFO
+// RUN: mlir-translate -mlir-to-llvmir -split-input-file -verify-diagnostics %s | FileCheck %s --check-prefix=CHECK-LLVM
 
 module {
   // GENERIC: "llvm.func"
   // GENERIC: function_type = !llvm.func<void ()>
   // GENERIC-SAME: sym_name = "foo"
   // GENERIC-SAME: () -> ()
   // CHECK: llvm.func @foo()
-  "llvm.func"() ({
+  "llvm.func" () ({
   }) {sym_name = "foo", function_type = !llvm.func<void ()>} : () -> ()
 
   // GENERIC: "llvm.func"
   // GENERIC: function_type = !llvm.func<i64 (i64, i64)>
   // GENERIC-SAME: sym_name = "bar"
   // GENERIC-SAME: () -> ()
   // CHECK: llvm.func @bar(i64, i64) -> i64
   "llvm.func"() ({
llvm.func internal @internal_func() {
     llvm.return
   }
 
   // CHECK: llvm.func weak
   llvm.func weak @weak_linkage() {
     llvm.return
   }
 
+  // CHECK-LLVM: define ptx_kernel void @calling_conv
+  llvm.func ptx_kernelcc @calling_conv() {
+    llvm.return
+  }
+
   // Omit the `external` linkage, which is the default, in the custom format.
   // Check that it is present in the generic format using its numeric value.
   //
   // CHECK: llvm.func @external_func
   // GENERIC: linkage = #llvm.linkage<external>
   llvm.func external @external_func()
 
   // CHECK-LABEL: llvm.func @arg_struct_attr(