path: root/source/compiler-core/slang-nvrtc-compiler.cpp

// slang-nvrtc-compiler.cpp
#include "slang-nvrtc-compiler.h"

#include "../core/slang-common.h"
#include "../../slang-com-helper.h"

#include "../core/slang-blob.h"

#include "../core/slang-string-util.h"
#include "../core/slang-string-slice-pool.h"

#include "../core/slang-io.h"
#include "../core/slang-shared-library.h"
#include "../core/slang-semantic-version.h"

#include "../core/slang-shared-library.h"

namespace nvrtc
{

typedef enum {
  NVRTC_SUCCESS = 0,
  NVRTC_ERROR_OUT_OF_MEMORY = 1,
  NVRTC_ERROR_PROGRAM_CREATION_FAILURE = 2,
  NVRTC_ERROR_INVALID_INPUT = 3,
  NVRTC_ERROR_INVALID_PROGRAM = 4,
  NVRTC_ERROR_INVALID_OPTION = 5,
  NVRTC_ERROR_COMPILATION = 6,
  NVRTC_ERROR_BUILTIN_OPERATION_FAILURE = 7,
  NVRTC_ERROR_NO_NAME_EXPRESSIONS_AFTER_COMPILATION = 8,
  NVRTC_ERROR_NO_LOWERED_NAMES_BEFORE_COMPILATION = 9,
  NVRTC_ERROR_NAME_EXPRESSION_NOT_VALID = 10,
  NVRTC_ERROR_INTERNAL_ERROR = 11
} nvrtcResult;

typedef struct _nvrtcProgram *nvrtcProgram;

#define SLANG_NVRTC_FUNCS(x) \
    x(const char*, nvrtcGetErrorString, (nvrtcResult result)) \
    x(nvrtcResult, nvrtcVersion, (int *major, int *minor)) \
    x(nvrtcResult, nvrtcCreateProgram, (nvrtcProgram *prog, const char *src, const char *name, int numHeaders, const char * const *headers, const char * const *includeNames)) \
    x(nvrtcResult, nvrtcDestroyProgram, (nvrtcProgram *prog)) \
    x(nvrtcResult, nvrtcCompileProgram, (nvrtcProgram prog, int numOptions, const char * const *options)) \
    x(nvrtcResult, nvrtcGetPTXSize, (nvrtcProgram prog, size_t *ptxSizeRet)) \
    x(nvrtcResult, nvrtcGetPTX, (nvrtcProgram prog, char *ptx)) \
    x(nvrtcResult, nvrtcGetProgramLogSize, (nvrtcProgram prog, size_t *logSizeRet)) \
    x(nvrtcResult, nvrtcGetProgramLog, (nvrtcProgram prog, char *log))\
    x(nvrtcResult, nvrtcAddNameExpression, (nvrtcProgram prog, const char * const name_expression)) \
    x(nvrtcResult, nvrtcGetLoweredName, (nvrtcProgram prog, const char *const name_expression, const char** lowered_name))

} // namespace nvrtc

namespace Slang
{
using namespace nvrtc;

static SlangResult _asResult(nvrtcResult res)
{
    switch (res)
    {
        case NVRTC_SUCCESS:
        {
            return SLANG_OK;
        }
        case NVRTC_ERROR_OUT_OF_MEMORY:
        {
            return SLANG_E_OUT_OF_MEMORY;
        }
        case NVRTC_ERROR_PROGRAM_CREATION_FAILURE: 
        case NVRTC_ERROR_INVALID_INPUT:
        case NVRTC_ERROR_INVALID_PROGRAM:
        {
            return SLANG_FAIL;
        }
        case NVRTC_ERROR_INVALID_OPTION:
        {
            return SLANG_E_INVALID_ARG;
        }
        case NVRTC_ERROR_COMPILATION:
        case NVRTC_ERROR_BUILTIN_OPERATION_FAILURE:
        case NVRTC_ERROR_NO_NAME_EXPRESSIONS_AFTER_COMPILATION:
        case NVRTC_ERROR_NO_LOWERED_NAMES_BEFORE_COMPILATION:
        case NVRTC_ERROR_NAME_EXPRESSION_NOT_VALID:
        {
            return SLANG_FAIL;
        }
        case NVRTC_ERROR_INTERNAL_ERROR:
        {
            return SLANG_E_INTERNAL_FAIL;
        }
        default: return SLANG_FAIL;
    }
}

class NVRTCDownstreamCompiler : public DownstreamCompiler
{
public:
    typedef DownstreamCompiler Super;

    // DownstreamCompiler
    virtual SlangResult compile(const CompileOptions& options, RefPtr<DownstreamCompileResult>& outResult) SLANG_OVERRIDE;
    virtual bool isFileBased() SLANG_OVERRIDE { return false; }

        /// Must be called before use
    SlangResult init(ISlangSharedLibrary* library);

    NVRTCDownstreamCompiler() {}
    
protected:

    struct ScopeProgram
    {
        ScopeProgram(NVRTCDownstreamCompiler* compiler, nvrtcProgram program):
            m_compiler(compiler),
            m_program(program)
        {
        }
        ~ScopeProgram()
        {
            m_compiler->m_nvrtcDestroyProgram(&m_program);
        }
        NVRTCDownstreamCompiler* m_compiler;
        nvrtcProgram m_program;
    };

    SlangResult _findIncludePath(String& outIncludePath);

    SlangResult _getIncludePath(String& outIncludePath);

    SlangResult _maybeAddHalfSupport(const CompileOptions& options, CommandLine& ioCmdLine);

#define SLANG_NVTRC_MEMBER_FUNCS(ret, name, params) \
    ret (*m_##name) params;

    SLANG_NVRTC_FUNCS(SLANG_NVTRC_MEMBER_FUNCS);

    // Holds list of paths passed in where cuda_fp16.h is found. Does *NOT* include cuda_fp16.h.
    List<String> m_cudaFp16FoundPaths;

    bool m_includeSearched = false;
    // Holds location of where include (for cuda_fp16.h) is found. 
    String m_includePath;

    ComPtr<ISlangSharedLibrary> m_sharedLibrary;  
};

#define SLANG_NVRTC_RETURN_ON_FAIL(x) { nvrtcResult _res = x; if (_res != NVRTC_SUCCESS) return _asResult(_res); } 

SlangResult NVRTCDownstreamCompiler::init(ISlangSharedLibrary* library)
{
#define SLANG_NVTRC_GET_FUNC(ret, name, params)  \
    m_##name = (ret (*) params)library->findFuncByName(#name); \
    if (m_##name == nullptr) return SLANG_FAIL;

    SLANG_NVRTC_FUNCS(SLANG_NVTRC_GET_FUNC)

    m_sharedLibrary = library;

    m_desc.type = SLANG_PASS_THROUGH_NVRTC;

    int major, minor;
    m_nvrtcVersion(&major, &minor);
    m_desc.majorVersion = major;
    m_desc.minorVersion = minor;

    return SLANG_OK;
}

static SlangResult _parseLocation(const UnownedStringSlice& in, DownstreamDiagnostic& outDiagnostic)
{
    const Index startIndex = in.indexOf('(');

    if (startIndex >= 0)
    {
        outDiagnostic.filePath = UnownedStringSlice(in.begin(), in.begin() + startIndex);
        UnownedStringSlice remaining(in.begin() + startIndex + 1, in.end());
        const Int endIndex = remaining.indexOf(')');

        UnownedStringSlice lineText = UnownedStringSlice(remaining.begin(), remaining.begin() + endIndex);

        Int line;
        SLANG_RETURN_ON_FAIL(StringUtil::parseInt(lineText, line));
        outDiagnostic.fileLine = line;
    }
    else
    {
        outDiagnostic.fileLine = 0;
        outDiagnostic.filePath = in;
    }
    return SLANG_OK;
}

static bool _isDriveLetter(char c)
{
    return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');
}

static bool _hasDriveLetter(const UnownedStringSlice& line)
{
    return line.getLength() > 2 && line[1] == ':' && _isDriveLetter(line[0]);
}

static SlangResult _parseNVRTCLine(const UnownedStringSlice& line, DownstreamDiagnostic& outDiagnostic)
{
    typedef DownstreamDiagnostic Diagnostic;
    typedef Diagnostic::Severity Severity;

    outDiagnostic.stage = Diagnostic::Stage::Compile;

    List<UnownedStringSlice> split;
    if (_hasDriveLetter(line))
    {
        // The drive letter has :, which confuses things, so skip that and then fix up first entry 
        UnownedStringSlice lineWithoutDrive(line.begin() + 2, line.end());
        StringUtil::split(lineWithoutDrive, ':', split);
        split[0] = UnownedStringSlice(line.begin(), split[0].end());
    }
    else
    {
        StringUtil::split(line, ':', split);
    }

    if (split.getCount() >= 3)
    {
        // tests/cuda/cuda-compile.cu(7): warning: variable "c" is used before its value is set

        const auto split1 = split[1].trim();

        if (split1 == "error")
        {
            outDiagnostic.severity = Severity::Error;
        }
        else if (split1 == "warning")
        {
            outDiagnostic.severity = Severity::Warning;
        }
        outDiagnostic.text = split[2].trim();

        SLANG_RETURN_ON_FAIL(_parseLocation(split[0], outDiagnostic));
        return SLANG_OK;
    }
   
    return SLANG_E_NOT_FOUND;
}

/* An implementation of Path::Visitor that can be used for finding NVRTC shared library installations. */
struct NVRTCPathVisitor : Path::Visitor
{
    struct Candidate
    {
        typedef Candidate ThisType;

        bool operator==(const ThisType& rhs) const { return path == rhs.path && version == rhs.version; }
        bool operator!=(const ThisType& rhs) const { return !(*this == rhs); }

        static Candidate make(const String& path, const SemanticVersion& version)
        {
            Candidate can;
            can.version = version;
            can.path = path;
            return can;
        }
        String path;
        SemanticVersion version;
    };

    Index findVersion(const SemanticVersion& version) const
    {
        const Index count = m_candidates.getCount();
        for (Index i = 0; i < count; ++i)
        {
            if (m_candidates[i].version == version)
            {
                return i;
            }
        }
        return -1;
    }

    static bool _orderCandiate(const Candidate& a, const Candidate& b) { return a.version < b.version; }
    void sortCandidates() { m_candidates.sort(_orderCandiate); }

    
#if SLANG_WINDOWS_FAMILY
    SlangResult getVersion(const UnownedStringSlice& filename, SemanticVersion& outVersion)
    {
        // Versions on windows of the form
        // nvrtc64_110_2.dll
        //          11 - Major
        //           0 Minor
        //           2 Patch
        Index endIndex = filename.indexOf('.');
        endIndex = (endIndex < 0) ? filename.getLength() : endIndex;

        // If we have a version slice, split it
        UnownedStringSlice versionSlice = UnownedStringSlice(filename.begin() + m_prefix.getLength(), filename.begin() + endIndex);

        if (versionSlice.getLength() <= 0)
        {
            return SLANG_E_NOT_FOUND;
        }
        Int patch = 0;
        UnownedStringSlice majorMinorSlice;
        {
            List<UnownedStringSlice> slices;
            StringUtil::split(versionSlice, '_', slices);
            if (slices.getCount() >= 2)
            {
                // We don't bother checking for error here, if it's not parsable, it will be 0
                StringUtil::parseInt(slices[1], patch);
            }
            majorMinorSlice = slices[0];
        }

        if (majorMinorSlice.getLength() < 2)
        {
            // Must be a major and minor
            return SLANG_FAIL;
        }

        UnownedStringSlice majorSlice = majorMinorSlice.head(majorMinorSlice.getLength() - 1);
        UnownedStringSlice minorSlice = majorMinorSlice.subString(majorMinorSlice.getLength() - 1, 1);

        Int major;
        Int minor;

        SLANG_RETURN_ON_FAIL(StringUtil::parseInt(majorSlice, major));
        SLANG_RETURN_ON_FAIL(StringUtil::parseInt(minorSlice, minor));

        outVersion = SemanticVersion(int(major), int(minor), int(patch));
        return SLANG_OK;
    }
#else
    // How the path is constructed depends on platform
    // https://docs.nvidia.com/cuda/nvrtc/index.html
    // TODO(JS): Handle version number depending on the platform - it's different for Windows/OSX/Linux
    SlangResult getVersion(const UnownedStringSlice& filename, SemanticVersion& outVersion)
    {
        SLANG_UNUSED(filename);
        SLANG_UNUSED(outVersion);
        return SLANG_E_NOT_IMPLEMENTED;
    }

#endif

    void accept(Path::Type type, const UnownedStringSlice& filename) SLANG_OVERRIDE
    {
        // Lets make sure it start's with nvrtc, but not worry about case
        if (type == Path::Type::File)
        {
            // If there is a defined extension, make sure it has it
            if (m_postfix.getLength() && filename.getLength() >= m_postfix.getLength())
            {
                // We test without case - really for windows
                UnownedStringSlice filenamePostfix = filename.tail(filename.getLength() - m_postfix.getLength());
                if (!filenamePostfix.caseInsensitiveEquals(m_postfix.getUnownedSlice()))
                {
                    return;
                }
            }

            
            if (filename.getLength() >= m_prefix.getLength() &&
                filename.subString(0, m_prefix.getLength()).caseInsensitiveEquals(m_prefix.getUnownedSlice()))
            {
                SemanticVersion version;
                // If it produces an error, just use 0.0.0
                if (SLANG_FAILED(getVersion(filename, version)))
                {
                    version = SemanticVersion();
                }

                // We may want to add multiple versions, if they are in different locations - as there may be multiple entries
                // in the PATH, and only one works. We'll only know which works by loading

#if 0
                // We already found this version, so let's not add it again
                if (findVersion(version) >= 0)
                {
                    return;
                }
#endif

                // Strip to make a shared library name
                UnownedStringSlice sharedLibraryName = filename.tail(m_prefix.getLength() - m_sharedLibraryStem.getLength());
                sharedLibraryName = filename.head(filename.getLength() - m_postfix.getLength());

                auto candidate = Candidate::make(Path::combine(m_basePath, sharedLibraryName), version);

                // If we already have this candidate, then skip
                if (m_candidates.indexOf(candidate) >= 0)
                {
                    return;
                }

                // Add to the list of candidates
                m_candidates.add(candidate);
            }
        }
    }

    SlangResult findInDirectory(const String& path)
    {
        m_basePath = path;
        return Path::find(path, nullptr, this);
    }

    bool hasCandidates() const { return m_candidates.getCount() > 0; }

    NVRTCPathVisitor(const UnownedStringSlice& sharedLibraryStem) :
        m_sharedLibraryStem(sharedLibraryStem)
    {
        // Work out the prefix and postfix of the shader
        StringBuilder buf;
        SharedLibrary::appendPlatformFileName(sharedLibraryStem, buf);
        const Index index = buf.indexOf(sharedLibraryStem);
        SLANG_ASSERT(index >= 0);

        m_prefix = buf.getUnownedSlice().head(index + sharedLibraryStem.getLength());
        m_postfix = buf.getUnownedSlice().tail(index + sharedLibraryStem.getLength());
    }

    String m_prefix;
    String m_postfix;
    String m_basePath;
    String m_sharedLibraryStem;

    List<Candidate> m_candidates;
};

template <typename T>
SLANG_FORCE_INLINE static void _unusedFunction(const T& func)
{
    SLANG_UNUSED(func);
}

#define SLANG_UNUSED_FUNCTION(x) _unusedFunction(x)

static UnownedStringSlice _getNVRTCBaseName()
{
#if SLANG_WINDOWS_FAMILY && SLANG_PTR_IS_64
    return UnownedStringSlice::fromLiteral("nvrtc64_");
#else
    return UnownedStringSlice::fromLiteral("nvrtc");
#endif
}

// Candidates are in m_candidates list. Will be ordered from the oldest to newest (in version number)
static SlangResult _findNVRTC(NVRTCPathVisitor& visitor)
{
    // First try the instance path (if supported on platform)
    {
        StringBuilder instancePath;
        if (SLANG_SUCCEEDED(PlatformUtil::getInstancePath(instancePath)))
        {
            visitor.findInDirectory(instancePath);
        }
    }

    // If we don't have a candidate try CUDA_PATH
    if (!visitor.hasCandidates())
    {
        StringBuilder buf;
        if (!SLANG_SUCCEEDED(PlatformUtil::getEnvironmentVariable(UnownedStringSlice::fromLiteral("CUDA_PATH"), buf)))
        {
            // Look for candidates in the directory
            visitor.findInDirectory(Path::combine(buf, "bin"));
        }
    }

    // If we haven't we go searching through PATH
    if (!visitor.hasCandidates())
    {
        List<UnownedStringSlice> splitPath;

        StringBuilder buf;
        if (SLANG_SUCCEEDED(PlatformUtil::getEnvironmentVariable(UnownedStringSlice::fromLiteral("PATH"), buf)))
        {
            // Split so we get individual paths
            List<UnownedStringSlice> paths;
            StringUtil::split(buf.getUnownedSlice(), ';', paths);

            // We use a pool to make sure we only check each path once
            StringSlicePool pool(StringSlicePool::Style::Empty);

            // We are going to search the paths in order 
            for (const auto& path : paths)
            {
                // PATH can have the same path multiple times. If we have already searched this path, we don't need to again
                if (!pool.has(path))
                {
                    pool.add(path);

                    Path::split(path, splitPath);

                    // We could search every path, but here we restrict to paths that look like CUDA installations.
                    // It's a path that contains a CUDA directory and has bin
                    if (splitPath.indexOf("CUDA") >= 0 && splitPath[splitPath.getCount() - 1].caseInsensitiveEquals(UnownedStringSlice::fromLiteral("bin")))
                    {
                        // Okay lets search it
                        visitor.findInDirectory(path);
                    }
                }
            }
        }
    }

    // Put into version order with oldest first. 
    visitor.sortCandidates();

    return SLANG_OK;
}    

static const UnownedStringSlice g_fp16HeaderName = UnownedStringSlice::fromLiteral("cuda_fp16.h");

SlangResult NVRTCDownstreamCompiler::_getIncludePath(String& outPath)
{
    if (!m_includeSearched)
    {
        m_includeSearched = true;

        SLANG_ASSERT(m_includePath.getLength() == 0);

        _findIncludePath(m_includePath);
    }

    outPath = m_includePath;
    return m_includePath.getLength() ? SLANG_OK : SLANG_E_NOT_FOUND;
}

SlangResult _findFileInIncludePath(const String& path, const UnownedStringSlice& filename, String& outPath)
{
    if (File::exists(Path::combine(path, filename)))
    {
        outPath = path;
        return SLANG_OK;
    }

    {
        String includePath = Path::combine(path, "include");
        if (File::exists(Path::combine(includePath, filename)))
        {
            outPath = includePath;
            return SLANG_OK;
        }
    }

    {
        String cudaIncludePath = Path::combine(path, "CUDA/include");
        if (File::exists(Path::combine(cudaIncludePath, filename)))
        {
            outPath = cudaIncludePath;
            return SLANG_OK;
        }
    }

    return SLANG_E_NOT_FOUND;
}

SlangResult NVRTCDownstreamCompiler::_findIncludePath(String& outPath)
{
    outPath = String();

    // Try looking up from a symbol. This will work as long as the nvrtc is loaded somehow from a dll/sharedlibrary
    // And the header is included from there
    {
        String libPath = SharedLibraryUtils::getSharedLibraryFileName((void*)m_nvrtcCreateProgram);
        if (libPath.getLength())
        {
            const String parentPath = Path::getParentDirectory(libPath);
            if (SLANG_SUCCEEDED(_findFileInIncludePath(parentPath, g_fp16HeaderName, outPath)))
            {
                return SLANG_OK;
            }
        }
    }

    // Try CUDA_PATH environment variable
    {
        StringBuilder buf;
        if (SLANG_SUCCEEDED(PlatformUtil::getEnvironmentVariable(UnownedStringSlice::fromLiteral("CUDA_PATH"), buf)))
        {
            String includePath = Path::combine(buf, "include");

            if (File::exists(Path::combine(includePath, g_fp16HeaderName)))
            {
                outPath = includePath;
                return SLANG_OK;
            }
        }
    }

    return SLANG_E_NOT_FOUND;
}

SlangResult NVRTCDownstreamCompiler::_maybeAddHalfSupport(const CompileOptions& options, CommandLine& ioCmdLine)
{
    if ((options.flags & CompileOptions::Flag::EnableFloat16) == 0)
    {
        return SLANG_OK;
    }

    // First check if we know if one of the include paths contains cuda_fp16.h
    for (const auto& includePath : options.includePaths)
    {
        if (m_cudaFp16FoundPaths.indexOf(includePath) >= 0)
        {
            // Okay we have an include path that we know works.
            // Just need to enable HALF in prelude
            ioCmdLine.addArg("-DSLANG_CUDA_ENABLE_HALF");
            return SLANG_OK;
        }
    }

    // Let's see if one of the paths finds cuda_fp16.h
    for (const auto& includePath : options.includePaths)
    {
        const String checkPath = Path::combine(includePath, g_fp16HeaderName);
        if (File::exists(checkPath))
        {
            m_cudaFp16FoundPaths.add(includePath);
            // Just need to enable HALF in prelude
            ioCmdLine.addArg("-DSLANG_CUDA_ENABLE_HALF");
            return SLANG_OK;
        }
    }

    String includePath;
    SLANG_RETURN_ON_FAIL(_getIncludePath(includePath));

    // Add the found include path
    ioCmdLine.addArg("-I");
    ioCmdLine.addArg(includePath);

    ioCmdLine.addArg("-DSLANG_CUDA_ENABLE_HALF");

    return SLANG_OK;
}

SlangResult NVRTCDownstreamCompiler::compile(const CompileOptions& options, RefPtr<DownstreamCompileResult>& outResult)
{
    // This compiler doesn't read files, they should be read externally and stored in sourceContents/sourceContentsPath
    if (options.sourceFiles.getCount() > 0)
    {
        return SLANG_FAIL;
    }

    CommandLine cmdLine;

    switch (options.debugInfoType)
    {
        case DebugInfoType::None:
        {
            break;
        }
        default:
        {
            cmdLine.addArg("--device-debug");
            break;
        }
        case DebugInfoType::Maximal:
        {
            cmdLine.addArg("--device-debug");
            cmdLine.addArg("--generate-line-info");
            break;
        }
    }

    // Don't seem to have such a control, so ignore for now
    //switch (options.optimizationLevel)
    //{
    //    default: break;
    //}

    switch (options.floatingPointMode)
    {
        case FloatingPointMode::Default: break;
        case FloatingPointMode::Precise:
        {
            break;
        }
        case FloatingPointMode::Fast:
        {
            cmdLine.addArg("--use_fast_math");
            break;
        }
    }

    // Add defines
    for (const auto& define : options.defines)
    {
        StringBuilder builder;
        builder << "-D";
        builder << define.nameWithSig;
        if (define.value.getLength())
        {
            builder << "=" << define.value;
        }

        cmdLine.addArg(builder);
    }

    // Add includes
    for (const auto& include : options.includePaths)
    {
        cmdLine.addArg("-I");
        cmdLine.addArg(include);
    }

    SLANG_RETURN_ON_FAIL(_maybeAddHalfSupport(options, cmdLine));

    // Neither of these options are strictly required, for general use of nvrtc,
    // but are enabled to make use withing Slang work more smoothly
    {
        // Require c++14, as makes initialization construction with {} available and so simplifies code generation
        cmdLine.addArg("-std=c++14");

        // Disable all warnings
        // This is arguably too much - but nvrtc does not appear to have a mechanism to switch off individual warnings.
        // I tried the -Xcudafe mechanism but that does not appear to work for nvrtc
        cmdLine.addArg("-w");
    }

    {
        // The lowest supported CUDA architecture version supported
        // by NVRTC is `compute_30`.
        //
        SemanticVersion version(3);

        // Newer releases of NVRTC only support `compute_35` and up
        // (with everything before `compute_52` being deprecated).
        //
        if( m_desc.majorVersion >= 11 )
        {
            version = SemanticVersion(3, 5);
        }

        // If constructs used in the code to be compield require
        // a higher architecture version than the minimum, then
        // we will set the version to the highest version listed
        // among the requirements.
        //
        for (const auto& capabilityVersion : options.requiredCapabilityVersions)
        {
            if (capabilityVersion.kind == DownstreamCompiler::CapabilityVersion::Kind::CUDASM)
            {
                if (capabilityVersion.version > version)
                {
                    version = capabilityVersion.version;
                }
            }
        }

        StringBuilder builder;
        builder << "-arch=compute_";
        builder << version.m_major;

        SLANG_ASSERT(version.m_minor >= 0 && version.m_minor <= 9);
        builder << char('0' + version.m_minor);

        cmdLine.addArg(builder);
    }

    List<const char*> headers;
    List<const char*> headerIncludeNames;

    // If compiling for OptiX, we need to add the appropriate search paths to the command line.
    //
    if(options.pipelineType == PipelineType::RayTracing)
    {
        // The device-side OptiX API is accessed through a constellation
        // of headers provided by the OptiX SDK, so we need to set an
        // include path for the compile that makes those visible.
        //
        // TODO: The OptiX SDK installer doesn't set any kind of environment
        // variable to indicate where the SDK was installed, so we seemingly
        // need to probe paths instead. The form of the path will differ
        // betwene Windows and Unix-y platforms, and we will need some kind
        // of approach to probe multiple versiosn and use the latest.
        //
        // HACK: For now I'm using the fixed path for the most recent SDK
        // release on Windows. This means that OptiX cross-compilation will
        // only "work" on a subset of platforms, but that doesn't matter
        // for now since it doesn't really "work" at all.
        //
        cmdLine.addArg("-I");
        cmdLine.addArg("C:/ProgramData/NVIDIA Corporation/OptiX SDK 7.0.0/include/");

        // The OptiX headers in turn `#include <stddef.h>` and expect that
        // to work. We could try to also add in an include path from the CUDA
        // SDK (which seems to provide a `stddef.h` in the most recent version),
        // but using that version doesn't seem to work (and also bakes in a
        // requirement that the user have the CUDA SDK installed in addition
        // to the OptiX SDK).
        //
        // Instead, we will rely on the NVRTC feature that lets us set up
        // memory buffers to be used as include files by the we compile.
        // We will define a dummy `stddef.h` that includes the bare minimum
        // lines required to get the OptiX headers to compile without complaint.
        //
        // TODO: Confirm that the `LP64` definition here is actually needed.
        //
        headerIncludeNames.add("stddef.h");
        headers.add("#pragma once\n" "#define LP64\n");

        // Finally, we want the CUDA prelude to be able to react to whether
        // or not OptiX is required (most notably by `#include`ing the appropriate
        // header(s)), so we will insert a preprocessor define to indicate
        // the requirement.
        //
        cmdLine.addArg("-DSLANG_CUDA_ENABLE_OPTIX");
    }

    SLANG_ASSERT(headers.getCount() == headerIncludeNames.getCount());

    nvrtcProgram program = nullptr;
    nvrtcResult res = m_nvrtcCreateProgram(&program, options.sourceContents.getBuffer(), options.sourceContentsPath.getBuffer(),
        (int) headers.getCount(),
        headers.getBuffer(),
        headerIncludeNames.getBuffer());
    if (res != NVRTC_SUCCESS)
    {
        return _asResult(res);
    }
    ScopeProgram scope(this, program);

    List<const char*> dstOptions;
    dstOptions.setCount(cmdLine.m_args.getCount());
    for (Index i = 0; i < cmdLine.m_args.getCount(); ++i)
    {
        dstOptions[i] = cmdLine.m_args[i].getBuffer();
    }

    res  = m_nvrtcCompileProgram(program, int(dstOptions.getCount()), dstOptions.getBuffer());

    RefPtr<ListBlob> blob;
    DownstreamDiagnostics diagnostics;

    diagnostics.result = _asResult(res);

    {
        String rawDiagnostics;

        size_t logSize = 0;
        SLANG_NVRTC_RETURN_ON_FAIL(m_nvrtcGetProgramLogSize(program, &logSize));

        if (logSize)
        {
            char* dst = rawDiagnostics.prepareForAppend(Index(logSize));
            SLANG_NVRTC_RETURN_ON_FAIL(m_nvrtcGetProgramLog(program, dst));
            rawDiagnostics.appendInPlace(dst, Index(logSize));

            diagnostics.rawDiagnostics = rawDiagnostics;
        }

        // Parse the diagnostics here
        for (auto line : LineParser(diagnostics.rawDiagnostics.getUnownedSlice()))
        {
            DownstreamDiagnostic diagnostic;
            SlangResult lineRes = _parseNVRTCLine(line, diagnostic);

            if (SLANG_SUCCEEDED(lineRes))
            {
                diagnostics.diagnostics.add(diagnostic);
            }
            else if (lineRes != SLANG_E_NOT_FOUND)
            {
                return lineRes;
            }
        }

        // if it has a compilation error.. set on output
        if (diagnostics.has(DownstreamDiagnostic::Severity::Error))
        {
            diagnostics.result = SLANG_FAIL;
        }
    }

    if (res == nvrtc::NVRTC_SUCCESS)
    {
        // We should parse the log to set up the diagnostics
        size_t ptxSize;
        SLANG_NVRTC_RETURN_ON_FAIL(m_nvrtcGetPTXSize(program, &ptxSize));

        List<uint8_t> ptx;
        ptx.setCount(Index(ptxSize));

        SLANG_NVRTC_RETURN_ON_FAIL(m_nvrtcGetPTX(program, (char*)ptx.getBuffer()));

        blob = ListBlob::moveCreate(ptx);
    }

    outResult = new BlobDownstreamCompileResult(diagnostics, blob);

    return SLANG_OK;
}



static SlangResult _findAndLoadNVRTC(ISlangSharedLibraryLoader* loader, ComPtr<ISlangSharedLibrary>& outLibrary)
{
#if SLANG_WINDOWS_FAMILY && SLANG_PTR_IS_64

    // We only need to search 64 bit versions on windows 
    NVRTCPathVisitor visitor(_getNVRTCBaseName());
    SLANG_RETURN_ON_FAIL(_findNVRTC(visitor));

    // We want to start with the newest version...
    for (Index i = visitor.m_candidates.getCount() - 1; i >= 0; --i)
    {
        const auto& candidate = visitor.m_candidates[i];
        if (SLANG_SUCCEEDED(loader->loadSharedLibrary(candidate.path.getBuffer(), outLibrary.writeRef())))
        {
            return SLANG_OK;
        }
    }

#else
    SLANG_UNUSED(loader);
    SLANG_UNUSED(outLibrary);

    SLANG_UNUSED_FUNCTION(_getNVRTCBaseName);
    SLANG_UNUSED_FUNCTION(_findNVRTC);
#endif

    // This is an official-ish list of versions is here:
    // https://developer.nvidia.com/cuda-toolkit-archive
    
    // Filenames for NVRTC
    // https://docs.nvidia.com/cuda/nvrtc/index.html
    //
    // From this it appears on platforms other than windows the SharedLibrary name
    // should be nvrtc which is already tried, so we can give up now. 
    return SLANG_E_NOT_FOUND;
}

/* static */SlangResult NVRTCDownstreamCompilerUtil::locateCompilers(const String& path, ISlangSharedLibraryLoader* loader, DownstreamCompilerSet* set)
{
    ComPtr<ISlangSharedLibrary> library;

    // If the user supplies a path to their preferred version of NVRTC,
    // we just use this.
    if (path.getLength() != 0)
    {
        SLANG_RETURN_ON_FAIL(loader->loadSharedLibrary(path.getBuffer(), library.writeRef()));
    }
    else
    {
        // As a catch-all for non-Windows platforms, we search for
        // a library simply named `nvrtc` (well, `libnvrtc`) which
        // is expected to match whatever the user has installed.
        //
        // On Windows an installation could place the version of nvrtc it uses in the same directory
        // as the slang binary, such that it's loaded.
        // Using this name also allows a ISlangSharedLibraryLoader to easily identify what is required
        // and perhaps load a specific version
        if (SLANG_FAILED(loader->loadSharedLibrary("nvrtc", library.writeRef())))
        {
            // Try something more sophisticated to locate NVRTC
            SLANG_RETURN_ON_FAIL(_findAndLoadNVRTC(loader, library));
        }
    }

    SLANG_ASSERT(library);
    if (!library)
    {
        return SLANG_FAIL;
    }

    RefPtr<NVRTCDownstreamCompiler> compiler(new NVRTCDownstreamCompiler);
    SLANG_RETURN_ON_FAIL(compiler->init(library));

    set->addCompiler(compiler);
    return SLANG_OK;
}

}