[MLIR] UnknownLoc on Inlinable Calls in LLVMIR Translation

[manbearian]

Summary

During MLIR translation to LLVMIR if an inlineable call has an UnkownLoc we get this error message:

inlinable function call in a function with debug info must have a !dbg location   
  call void @callee()

There is code that checks for this case and strips debug information to avoid this situation. I'm expanding this code to handle the case where an debug location points at a UnknownLoc. For example, a NamedLoc whose child location is an UnknownLoc.

mlir/lib/Target/LLVMIR/DebugTranslation.cpp

void DebugTranslation::translate(LLVMFuncOp func, llvm::Function &llvmFunc) {
   // translate.
   if (!compileUnit || !func.walk(interruptIfValidLocation).wasInterrupted())
     return;
 
   // If we are to create debug info for the function, we need to ensure that all
   // inlinable calls in it are with debug info, otherwise the LLVM verifier will
   // complain. For now, be more restricted and treat all calls as inlinable.
   const bool hasCallWithoutDebugInfo =
-      func.walk([](LLVM::CallOp call) {
-            return call.getLoc().isa<UnknownLoc>() ? WalkResult::interrupt()
-                                                   : WalkResult::advance();
+      func.walk([&](LLVM::CallOp call) {
+            return call.getLoc()->walk([](Location l) {
+              return l.isa<UnknownLoc>() ? WalkResult::interrupt()
+            });
           })
           .wasInterrupted();
   if (hasCallWithoutDebugInfo)
     return;
 
   FileLineColLoc fileLoc = extractFileLoc(func.getLoc());
   auto *file =
       translateFile(fileLoc ? fileLoc.getFilename().strref() : "<unknown>");

mlir/test/Target/LLVMIR/llvmir-debug.mlir

 // RUN: mlir-translate -mlir-to-llvmir %s | FileCheck %s
 
+// CHECK-LABEL: define void @func_with_empty_named_info()
+// Check that translation doens't crash in the presence of an inlineble call
+// with a named loc that has no backing source info.
+llvm.func @callee() {
+  llvm.return
+} loc("calleesource.cc":1:1)
+llvm.func @func_with_empty_named_info() {
+  llvm.call @callee() : () -> () loc("named with no line info")
+  llvm.return
+}
+
 // CHECK-LABEL: define void @func_no_debug()
 // CHECK-NOT: !dbg
 llvm.func @func_no_debug() {
   llvm.return loc(unknown)
 } loc(unknown)
 
 // CHECK-LABEL: define void @func_with_debug()
 // CHECK-SAME: !dbg ![[FUNC_LOC:[0-9]+]]