[SYCL] Improve the error mechanism of llvm-no-spir-kernel (#1068)

This patch improves the tool's diagnostic upon finding a
SPIR kernel within an LLVM module. Despite that the tool's
only current use is within the SYCL FPGA flow, it's important
to make the message target-agnostic, so that the tool is not
tied to a particular device BE.
A related commit to the Clang driver has extended these diagnostics
with SYCL FPGA specifics without affecting the tool itself.

This patch also introduces testing for the return code value. For
example, this should allow the Clang driver users/developers to
differentiate between the two possible causes of llvm-no-spir-kernel
failure.

Signed-off-by: Artem Gindinson <artem.gindinson@intel.com>

Author: Artem Gindinson

llvm/test/tools/llvm-no-spir-kernel/error-code.ll

@@ -0,0 +1,11 @@
+; UNSUPPORTED: system-windows
+
+; Check the return code
+; RUN: llvm-no-spir-kernel %s; \
+; RUN: if [ $? = 1 ]; then exit 0; else exit 1; fi
+
+; expected failure
+define spir_kernel void @foo() {
+bb:
+  ret void
+}

llvm/test/tools/llvm-no-spir-kernel/has-spir-kernel.ll

@@ -1,9 +1,15 @@
-; RUN: not llvm-no-spir-kernel  %s 
+; RUN: not llvm-no-spir-kernel %s 2>&1 | FileCheck %s
 
-; expected failure
-define spir_kernel void @foo() {
+; expected no failures
+define void @foo() {
 bb:
   ret void
 }
 
-
+; expected failure
+; CHECK: error: Unexpected SPIR kernel occurrence:
+; CHECK-SAME: foo2
+define spir_kernel void @foo2() {
+bb:
+  ret void
+}

llvm/test/tools/llvm-no-spir-kernel/has-spir-kernel2.ll

@@ -0,0 +1,2 @@
+; RUN: echo garbage > garbage.ll
+; RUN: not llvm-no-spir-kernel garbage.ll

llvm/test/tools/llvm-no-spir-kernel/invalid-input.ll

@@ -6,15 +6,20 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This utility checks if the input module contains functions that is a spir
-// kernel. Return 0 if no, return 1 if yes. Use of an output file is not
-// required for a successful check. It is used to allow for proper input and
-// output flow within the driver toolchain.
+// This utility checks if the input module contains functions that are a SPIR
+// kernel.
+//
+// - Return 0 if the LLVM module is "clean" from SPIR kernels
+// - Return 1 upon the first SPIR kernel occurence
+//
+// Use of an output file is not required for a successful check. It is used
+// to allow for proper input and output flow within the driver toolchain.
 //
 // Usage: llvm-no-spir-kernel input.bc/input.ll -o output.bc/output.ll
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Demangle/Demangle.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IRReader/IRReader.h"
@@ -44,15 +49,21 @@ int main(int argc, char **argv) {
 
   // Use lazy loading, since we only care about function calling convention
   SMDiagnostic Err;
+  const char *ProgramName = llvm::sys::path::filename(argv[0]).data();
   std::unique_ptr<Module> M = getLazyIRFileModule(InputFilename, Err, Context);
 
   if (!M.get()) {
-    Err.print(argv[0], errs());
+    Err.print(ProgramName, errs());
     return 1;
   }
 
   for (auto &F : *M) {
     if (F.getCallingConv() == CallingConv::SPIR_KERNEL) {
+      std::string SPIRKernelMsg =
+          "Unexpected SPIR kernel occurrence: " + demangle(F.getName().str());
+      SMDiagnostic SPIRKernelDiag(InputFilename, SourceMgr::DiagKind::DK_Error,
+                                  SPIRKernelMsg);
+      SPIRKernelDiag.print(ProgramName, errs());
       return 1;
     }
   }