[spirv-to-ir-wrapper] Prevent non-IR from being passed along (#5688)

Introduce an option -skip-unknown-input which can be used to prevent unknown
files from being passed through the tool.  There are usage models involving
archives in which the 'fat archives' do not contain all fat objects.  In
the case where this occurs, provide a way to prevent the non-IR object
from the device side to be passed through as it is not valid at the
device link step.

Author: mdtoguchi

llvm/test/tools/spirv-to-ir-wrapper/skip-unknown-input.txt

@@ -0,0 +1,9 @@
+; RUN: spirv-to-ir-wrapper %s -o %t.out -skip-unknown-input
+; RUN: FileCheck %s --input-file %t.out --allow-empty --check-prefix=CHECK_EMPTY
+; CHECK_EMPTY-NOT: JUST SOME TEXT
+
+; RUN: spirv-to-ir-wrapper %s -o %t2.out
+; RUN: FileCheck %s --input-file %t2.out --check-prefix=CHECK_PASSTHROUGH
+; CHECK_PASSTHROUGH: JUST SOME TEXT
+
+JUST SOME TEXT

llvm/test/tools/spirv-to-ir-wrapper/spirv-to-ir-wrapper.ll

@@ -1,6 +1,6 @@
 ; Check for passthrough abilities
 ; RUN: llvm-as %s -o %t.bc
-; RUN: spirv-to-ir-wrapper %t.bc -o %t_1.bc
+; RUN: spirv-to-ir-wrapper %t.bc -o %t_1.bc -skip-unknown-input
 ; RUN: llvm-dis %t_1.bc -o %t_1.ll
 ; RUN: FileCheck %s --input-file %t_1.ll
 

llvm/tools/spirv-to-ir-wrapper/spirv-to-ir-wrapper.cpp

@@ -26,6 +26,7 @@
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/InitLLVM.h"
 #include "llvm/Support/Path.h"
+#include "llvm/Support/Process.h"
 #include "llvm/Support/Program.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/StringSaver.h"
@@ -46,6 +47,12 @@ static cl::opt<std::string>
     LlvmSpirvOpts("llvm-spirv-opts", cl::value_desc("llvm-spirv options"),
                   cl::desc("options to pass to llvm-spirv"));
 
+// SkipUnknown - Skip unknown files (create empty output instead)
+static cl::opt<bool>
+    SkipUnknown("skip-unknown-input",
+                cl::desc("Only pass through files that are LLVM-IR or "
+                         "converted from SPIR-V"));
+
 static void error(const Twine &Message) {
   llvm::errs() << "spirv-to-ir-wrapper: " << Message << '\n';
   exit(1);
@@ -82,6 +89,14 @@ static int copyInputToOutput() {
   return llvm::sys::fs::copy_file(InputFilename, Output).value();
 }
 
+static int createEmptyOutput() {
+  int FD;
+  if (std::error_code EC = openFileForWrite(
+          Output, FD, sys::fs::CD_CreateAlways, sys::fs::OF_None))
+    return EC.value();
+  return llvm::sys::Process::SafelyCloseFileDescriptor(FD).value();
+}
+
 static bool isSPIRVBinary(const std::string &File) {
   auto FileOrError = MemoryBuffer::getFile(File, /*IsText=*/false,
                                            /*RequiresNullTerminator=*/false);
@@ -114,6 +129,9 @@ static int checkInputFileIsAlreadyLLVM(const char *Argv0) {
   if (Ext == "spv" || isSPIRVBinary(InputFilename))
     return convertSPIRVToLLVMIR(Argv0);
 
+  if (SkipUnknown)
+    return createEmptyOutput();
+
   // We could not directly determine the input file, so we just copy it
   // to the output file.
   return copyInputToOutput();