swr/rast: Implement JIT shader caching to disk

Disabled by default; currently doesn't cache shaders (fs,gs,vs).

Reviewed-by: Bruce Cherniak <[email protected]>

10 files changed, 358 insertions, 18 deletions

diff --git a/src/gallium/drivers/swr/rasterizer/codegen/knob_defs.py b/src/gallium/drivers/swr/rasterizer/codegen/knob_defs.py
index 0c39a77c741..02436f223ac 100644
--- a/src/gallium/drivers/swr/rasterizer/codegen/knob_defs.py
+++ b/src/gallium/drivers/swr/rasterizer/codegen/knob_defs.py
@@ -18,6 +18,7 @@
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 # FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 # IN THE SOFTWARE.
+import sys
 
 # Python source
 KNOBS = [
@@ -156,11 +157,25 @@ KNOBS = [
 
     ['DEBUG_OUTPUT_DIR', {
         'type'      : 'std::string',
-        'default'   : '/tmp/Rast/DebugOutput',
+        'default'   : r'%TEMP%\Rast\DebugOutput' if sys.platform == 'win32' else '/tmp/Rast/DebugOutput',
         'desc'      : ['Output directory for debug data.'],
         'category'  : 'debug',
     }],
 
+    ['JIT_ENABLE_CACHE', {
+        'type'      : 'bool',
+        'default'   : 'false',
+        'desc'      : ['Enables caching of compiled shaders'],
+        'category'  : 'debug',
+    }],
+
+    ['JIT_CACHE_DIR', {
+        'type'      : 'std::string',
+        'default'   : r'%TEMP%\SWR\JitCache' if sys.platform == 'win32' else '${HOME}/.swr/jitcache',
+        'desc'      : ['Cache directory for compiled shaders.'],
+        'category'  : 'debug',
+    }],
+
     ['TOSS_DRAW', {
         'type'      : 'bool',
         'default'   : 'false',
diff --git a/src/gallium/drivers/swr/rasterizer/codegen/templates/gen_knobs.cpp b/src/gallium/drivers/swr/rasterizer/codegen/templates/gen_knobs.cpp
index 81e49da659c..0527bf3b310 100644
--- a/src/gallium/drivers/swr/rasterizer/codegen/templates/gen_knobs.cpp
+++ b/src/gallium/drivers/swr/rasterizer/codegen/templates/gen_knobs.cpp
@@ -34,14 +34,44 @@
 #pragma once
 #include <string>
 
+struct KnobBase
+{
+private:
+    // Update the input string.
+    static void autoExpandEnvironmentVariables(std::string &text);
+
+protected:
+    // Leave input alone and return new string.
+    static std::string expandEnvironmentVariables(std::string const &input)
+    {
+        std::string text = input;
+        autoExpandEnvironmentVariables(text);
+        return text;
+    }
+
+    template <typename T>
+    static T expandEnvironmentVariables(T const &input)
+    {
+        return input;
+    }
+};
+
 template <typename T>
-struct Knob
+struct Knob : KnobBase
 {
+public:
     const   T&  Value() const               { return m_Value; }
-    const   T&  Value(const T& newValue)    { m_Value = newValue; return Value(); }
+    const   T&  Value(T const &newValue)
+    {
+        m_Value = expandEnvironmentVariables(newValue);
+        return Value();
+    }
 
 protected:
-    Knob(const T& defaultValue) : m_Value(defaultValue) {}
+    Knob(T const &defaultValue) :
+        m_Value(expandEnvironmentVariables(defaultValue))
+    {
+    }
 
 private:
     T m_Value;
@@ -102,6 +132,34 @@ extern GlobalKnobs g_GlobalKnobs;
 % for inc in includes:
 #include <${inc}>
 % endfor
+#include <regex>
+#include <core/utils.h>
+
+//========================================================
+// Implementation
+//========================================================
+void KnobBase::autoExpandEnvironmentVariables(std::string &text)
+{
+    {
+        static std::regex env("\\$\\{([^}]+)\\}");
+        std::smatch match;
+        while (std::regex_search(text, match, env))
+        {
+            const std::string var = GetEnv(match[1].str());
+            text.replace(match[0].first, match[0].second, var);
+        }
+    }
+    {
+        static std::regex env("\\%([^}]+)\\%");
+        std::smatch match;
+        while (std::regex_search(text, match, env))
+        {
+            const std::string var = GetEnv(match[1].str());
+            text.replace(match[0].first, match[0].second, var);
+        }
+    }
+}
+
 
 //========================================================
 // Static Data Members
diff --git a/src/gallium/drivers/swr/rasterizer/core/utils.h b/src/gallium/drivers/swr/rasterizer/core/utils.h
index 660a63fe4e3..28d10c755ef 100644
--- a/src/gallium/drivers/swr/rasterizer/core/utils.h
+++ b/src/gallium/drivers/swr/rasterizer/core/utils.h
@@ -1224,4 +1224,30 @@ struct TemplateArgUnroller
     }
 };
 
+//////////////////////////////////////////////////////////////////////////
+/// Helpers used to get / set environment variable
+//////////////////////////////////////////////////////////////////////////
+static INLINE std::string GetEnv(const std::string& variableName)
+{
+    std::string output;
+#if defined(_WIN32)
+    DWORD valueSize = GetEnvironmentVariableA(variableName.c_str(), nullptr, 0);
+    if (!valueSize) return output;
+    output.resize(valueSize - 1); // valueSize includes null, output.resize() does not
+    GetEnvironmentVariableA(variableName.c_str(), &output[0], valueSize);
+#else
+    output = getenv(variableName.c_str());
+#endif
+
+    return output;
+}
+
+static INLINE void SetEnv(const std::string& variableName, const std::string& value)
+{
+#if defined(_WIN32)
+    SetEnvironmentVariableA(variableName.c_str(), value.c_str());
+#else
+    setenv(variableName.c_str(), value.c_str(), true);
+#endif
+}
 
diff --git a/src/gallium/drivers/swr/rasterizer/jitter/JitManager.cpp b/src/gallium/drivers/swr/rasterizer/jitter/JitManager.cpp
index 49b06f738f4..60289cae1e1 100644
--- a/src/gallium/drivers/swr/rasterizer/jitter/JitManager.cpp
+++ b/src/gallium/drivers/swr/rasterizer/jitter/JitManager.cpp
@@ -46,6 +46,15 @@
 #include "llvm/IRReader/IRReader.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Support/FormattedStream.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/MemoryBuffer.h"
+
+#if HAVE_LLVM < 0x400
+#include "llvm/Bitcode/ReaderWriter.h"
+#else
+#include "llvm/Bitcode/BitcodeWriter.h"
+#include "llvm/Bitcode/BitcodeReader.h"
+#endif
 
 #if LLVM_USE_INTEL_JITEVENTS
 #include "llvm/ExecutionEngine/JITEventListener.h"
@@ -71,6 +80,11 @@
 #define JITTER_OUTPUT_DIR SWR_OUTPUT_DIR "\\Jitter"
 #endif // _WIN32
 
+#if defined(__APPLE) || defined(FORCE_LINUX) || defined(__linux__) || defined(__gnu_linux__)
+#include <pwd.h>
+#include <sys/stat.h>
+#endif
+
 
 using namespace llvm;
 using namespace SwrJit;
@@ -101,9 +115,7 @@ JitManager::JitManager(uint32_t simdWidth, const char *arch, const char* core)
     mCore = std::string(core);
     std::transform(mCore.begin(), mCore.end(), mCore.begin(), ::tolower);
 
-    std::stringstream fnName("JitModule", std::ios_base::in | std::ios_base::out | std::ios_base::ate);
-    fnName << mJitNumber++;
-    std::unique_ptr<Module> newModule(new Module(fnName.str(), mContext));
+    std::unique_ptr<Module> newModule(new Module("", mContext));
     mpCurrentModule = newModule.get();
 
     StringRef hostCPUName;
@@ -123,6 +135,12 @@ JitManager::JitManager(uint32_t simdWidth, const char *arch, const char* core)
         .setMCPU(hostCPUName)
         .create();
 
+    if (KNOB_JIT_ENABLE_CACHE)
+    {
+        mCache.SetCpu(hostCPUName);
+        mpExec->setObjectCache(&mCache);
+    }
+
 #if LLVM_USE_INTEL_JITEVENTS
     JITEventListener *vTune = JITEventListener::createIntelJITEventListener();
     mpExec->RegisterJITEventListener(vTune);
@@ -172,9 +190,7 @@ void JitManager::SetupNewModule()
 {
     SWR_ASSERT(mIsModuleFinalized == true && "Current module is not finalized!");
     
-    std::stringstream fnName("JitModule", std::ios_base::in | std::ios_base::out | std::ios_base::ate);
-    fnName << mJitNumber++;
-    std::unique_ptr<Module> newModule(new Module(fnName.str(), mContext));
+    std::unique_ptr<Module> newModule(new Module("", mContext));
     mpCurrentModule = newModule.get();
 #if defined(_WIN32)
     // Needed for MCJIT on windows
@@ -293,3 +309,194 @@ extern "C"
         }
     }
 }
+
+//////////////////////////////////////////////////////////////////////////
+/// JitCache
+//////////////////////////////////////////////////////////////////////////
+
+//////////////////////////////////////////////////////////////////////////
+/// JitCacheFileHeader
+//////////////////////////////////////////////////////////////////////////
+struct JitCacheFileHeader
+{
+    void Init(uint32_t llCRC, uint32_t objCRC, const std::string& moduleID, const std::string& cpu, uint64_t bufferSize)
+    {
+        m_MagicNumber = JC_MAGIC_NUMBER;
+        m_BufferSize = bufferSize;
+        m_llCRC = llCRC;
+        m_platformKey = JC_PLATFORM_KEY;
+        m_objCRC = objCRC;
+        strncpy(m_ModuleID, moduleID.c_str(), JC_STR_MAX_LEN - 1);
+        m_ModuleID[JC_STR_MAX_LEN - 1] = 0;
+        strncpy(m_Cpu, cpu.c_str(), JC_STR_MAX_LEN - 1);
+        m_Cpu[JC_STR_MAX_LEN - 1] = 0;
+    }
+
+    bool IsValid(uint32_t llCRC, const std::string& moduleID, const std::string& cpu)
+    {
+        if ((m_MagicNumber != JC_MAGIC_NUMBER) ||
+            (m_llCRC != llCRC) ||
+            (m_platformKey != JC_PLATFORM_KEY))
+        {
+            return false;
+        }
+
+        m_ModuleID[JC_STR_MAX_LEN - 1] = 0;
+        if (strncmp(moduleID.c_str(), m_ModuleID, JC_STR_MAX_LEN - 1))
+        {
+            return false;
+        }
+
+        m_Cpu[JC_STR_MAX_LEN - 1] = 0;
+        if (strncmp(cpu.c_str(), m_Cpu, JC_STR_MAX_LEN - 1))
+        {
+            return false;
+        }
+
+        return true;
+    }
+
+    uint64_t GetBufferSize() const { return m_BufferSize; }
+    uint64_t GetBufferCRC() const { return m_objCRC; }
+
+private:
+    static const uint64_t   JC_MAGIC_NUMBER = 0xfedcba9876543211ULL;
+    static const size_t     JC_STR_MAX_LEN = 32;
+    static const uint32_t   JC_PLATFORM_KEY =
+        (LLVM_VERSION_MAJOR << 24)  |
+        (LLVM_VERSION_MINOR << 16)  |
+        (LLVM_VERSION_PATCH << 8)   |
+        ((sizeof(void*) > sizeof(uint32_t)) ? 1 : 0);
+
+    uint64_t m_MagicNumber;
+    uint64_t m_BufferSize;
+    uint32_t m_llCRC;
+    uint32_t m_platformKey;
+    uint32_t m_objCRC;
+    char m_ModuleID[JC_STR_MAX_LEN];
+    char m_Cpu[JC_STR_MAX_LEN];
+};
+
+static inline uint32_t ComputeModuleCRC(const llvm::Module* M)
+{
+    std::string bitcodeBuffer;
+    raw_string_ostream bitcodeStream(bitcodeBuffer);
+
+    llvm::WriteBitcodeToFile(M, bitcodeStream);
+    //M->print(bitcodeStream, nullptr, false);
+
+    bitcodeStream.flush();
+
+    return ComputeCRC(0, bitcodeBuffer.data(), bitcodeBuffer.size());
+}
+
+/// constructor
+JitCache::JitCache()
+{
+#if defined(__APPLE) || defined(FORCE_LINUX) || defined(__linux__) || defined(__gnu_linux__)
+    if (strncmp(KNOB_JIT_CACHE_DIR.c_str(), "~/", 2) == 0) {
+        char *homedir;
+        if (!(homedir = getenv("HOME"))) {
+            homedir = getpwuid(getuid())->pw_dir;
+        }
+        mCacheDir = homedir;
+        mCacheDir += (KNOB_JIT_CACHE_DIR.c_str() + 1);
+    } else
+#endif
+    {
+        mCacheDir = KNOB_JIT_CACHE_DIR;
+    }
+}
+
+/// notifyObjectCompiled - Provides a pointer to compiled code for Module M.
+void JitCache::notifyObjectCompiled(const llvm::Module *M, llvm::MemoryBufferRef Obj)
+{
+    const std::string& moduleID = M->getModuleIdentifier();
+    if (!moduleID.length())
+    {
+        return;
+    }
+
+    if (!llvm::sys::fs::exists(mCacheDir.str()) &&
+        llvm::sys::fs::create_directories(mCacheDir.str()))
+    {
+        SWR_INVALID("Unable to create directory: %s", mCacheDir.c_str());
+        return;
+    }
+
+    llvm::SmallString<MAX_PATH> filePath = mCacheDir;
+    llvm::sys::path::append(filePath, moduleID);
+
+    std::error_code err;
+    llvm::raw_fd_ostream fileObj(filePath.c_str(), err, llvm::sys::fs::F_None);
+
+    uint32_t objcrc = ComputeCRC(0, Obj.getBufferStart(), Obj.getBufferSize());
+
+    JitCacheFileHeader header;
+    header.Init(mCurrentModuleCRC, objcrc, moduleID, mCpu, Obj.getBufferSize());
+
+    fileObj.write((const char*)&header, sizeof(header));
+    fileObj << Obj.getBuffer();
+    fileObj.flush();
+}
+
+/// Returns a pointer to a newly allocated MemoryBuffer that contains the
+/// object which corresponds with Module M, or 0 if an object is not
+/// available.
+std::unique_ptr<llvm::MemoryBuffer> JitCache::getObject(const llvm::Module* M)
+{
+    const std::string& moduleID = M->getModuleIdentifier();
+    mCurrentModuleCRC = ComputeModuleCRC(M);
+
+    if (!moduleID.length())
+    {
+        return nullptr;
+    }
+
+    if (!llvm::sys::fs::exists(mCacheDir))
+    {
+        return nullptr;
+    }
+
+    llvm::SmallString<MAX_PATH> filePath = mCacheDir;
+    llvm::sys::path::append(filePath, moduleID);
+
+    FILE* fpIn = fopen(filePath.c_str(), "rb");
+    if (!fpIn)
+    {
+        return nullptr;
+    }
+
+    std::unique_ptr<llvm::MemoryBuffer> pBuf = nullptr;
+    do
+    {
+        JitCacheFileHeader header;
+        if (!fread(&header, sizeof(header), 1, fpIn))
+        {
+            break;
+        }
+
+        if (!header.IsValid(mCurrentModuleCRC, moduleID, mCpu))
+        {
+            break;
+        }
+
+        pBuf = llvm::MemoryBuffer::getNewUninitMemBuffer(size_t(header.GetBufferSize()));
+        if (!fread(const_cast<char*>(pBuf->getBufferStart()), header.GetBufferSize(), 1, fpIn))
+        {
+            pBuf = nullptr;
+            break;
+        }
+
+        if (header.GetBufferCRC() != ComputeCRC(0, pBuf->getBufferStart(), pBuf->getBufferSize()))
+        {
+            SWR_TRACE("Invalid object cache file, ignoring: %s", filePath.c_str());
+            pBuf = nullptr;
+            break;
+        }
+    } while (0);
+
+    fclose(fpIn);
+
+    return pBuf;
+}
diff --git a/src/gallium/drivers/swr/rasterizer/jitter/JitManager.h b/src/gallium/drivers/swr/rasterizer/jitter/JitManager.h
index 97d93128de2..68377e70344 100644
--- a/src/gallium/drivers/swr/rasterizer/jitter/JitManager.h
+++ b/src/gallium/drivers/swr/rasterizer/jitter/JitManager.h
@@ -44,6 +44,7 @@
 #include "llvm/IR/Type.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/IntrinsicInst.h"
+#include "llvm/ExecutionEngine/ObjectCache.h"
 
 #include "llvm/Config/llvm-config.h"
 #ifndef LLVM_VERSION_MAJOR
@@ -78,6 +79,8 @@ using PassManager = llvm::legacy::PassManager;
 #include "common/os.h"
 #include "common/isa.hpp"
 
+#include <mutex>
+
 #pragma pop_macro("DEBUG")
 
 //////////////////////////////////////////////////////////////////////////
@@ -133,6 +136,31 @@ struct JitLLVMContext : llvm::LLVMContext
 {
 };
 
+//////////////////////////////////////////////////////////////////////////
+/// JitCache
+//////////////////////////////////////////////////////////////////////////
+class JitCache : public llvm::ObjectCache
+{
+public:
+    /// constructor
+    JitCache();
+    virtual ~JitCache() {}
+
+    void SetCpu(const llvm::StringRef& cpu) { mCpu = cpu.str(); }
+
+    /// notifyObjectCompiled - Provides a pointer to compiled code for Module M.
+    virtual void notifyObjectCompiled(const llvm::Module *M, llvm::MemoryBufferRef Obj);
+
+    /// Returns a pointer to a newly allocated MemoryBuffer that contains the
+    /// object which corresponds with Module M, or 0 if an object is not
+    /// available.
+    virtual std::unique_ptr<llvm::MemoryBuffer> getObject(const llvm::Module* M);
+
+private:
+    std::string mCpu;
+    llvm::SmallString<MAX_PATH> mCacheDir;
+    uint32_t mCurrentModuleCRC;
+};
 
 //////////////////////////////////////////////////////////////////////////
 /// JitManager
@@ -145,6 +173,7 @@ struct JitManager
     JitLLVMContext          mContext;   ///< LLVM compiler
     llvm::IRBuilder<>       mBuilder;   ///< LLVM IR Builder
     llvm::ExecutionEngine*  mpExec;
+    JitCache                mCache;
 
     // Need to be rebuilt after a JIT and before building new IR
     llvm::Module* mpCurrentModule;
diff --git a/src/gallium/drivers/swr/rasterizer/jitter/blend_jit.cpp b/src/gallium/drivers/swr/rasterizer/jitter/blend_jit.cpp
index 5daeea95d19..427884004f5 100644
--- a/src/gallium/drivers/swr/rasterizer/jitter/blend_jit.cpp
+++ b/src/gallium/drivers/swr/rasterizer/jitter/blend_jit.cpp
@@ -514,10 +514,8 @@ struct BlendJit : public Builder
 
     Function* Create(const BLEND_COMPILE_STATE& state)
     {
-        static std::size_t jitNum = 0;
-
-        std::stringstream fnName("BlendShader", std::ios_base::in | std::ios_base::out | std::ios_base::ate);
-        fnName << jitNum++;
+        std::stringstream fnName("BlendShader_", std::ios_base::in | std::ios_base::out | std::ios_base::ate);
+        fnName << ComputeCRC(0, &state, sizeof(state));
 
         // blend function signature
         //typedef void(*PFN_BLEND_JIT_FUNC)(const SWR_BLEND_STATE*, simdvector&, simdvector&, uint32_t, BYTE*, simdvector&, simdscalari*, simdscalari*);
@@ -536,6 +534,7 @@ struct BlendJit : public Builder
 
         FunctionType* fTy = FunctionType::get(IRB()->getVoidTy(), args, false);
         Function* blendFunc = Function::Create(fTy, GlobalValue::ExternalLinkage, fnName.str(), JM()->mpCurrentModule);
+        blendFunc->getParent()->setModuleIdentifier(blendFunc->getName());
 
         BasicBlock* entry = BasicBlock::Create(JM()->mContext, "entry", blendFunc);
 
diff --git a/src/gallium/drivers/swr/rasterizer/jitter/fetch_jit.cpp b/src/gallium/drivers/swr/rasterizer/jitter/fetch_jit.cpp
index 50c2e9b6bf0..8110a7d56f0 100644
--- a/src/gallium/drivers/swr/rasterizer/jitter/fetch_jit.cpp
+++ b/src/gallium/drivers/swr/rasterizer/jitter/fetch_jit.cpp
@@ -91,12 +91,14 @@ Function* FetchJit::Create(const FETCH_COMPILE_STATE& fetchState)
 {
     static std::size_t fetchNum = 0;
 
-    std::stringstream fnName("FetchShader", std::ios_base::in | std::ios_base::out | std::ios_base::ate);
-    fnName << fetchNum++;
+    std::stringstream fnName("FetchShader_", std::ios_base::in | std::ios_base::out | std::ios_base::ate);
+    fnName << ComputeCRC(0, &fetchState, sizeof(fetchState));
 
     Function*    fetch = Function::Create(JM()->mFetchShaderTy, GlobalValue::ExternalLinkage, fnName.str(), JM()->mpCurrentModule);
     BasicBlock*    entry = BasicBlock::Create(JM()->mContext, "entry", fetch);
 
+    fetch->getParent()->setModuleIdentifier(fetch->getName());
+
     IRB()->SetInsertPoint(entry);
 
     auto    argitr = fetch->arg_begin();
diff --git a/src/gallium/drivers/swr/rasterizer/jitter/jit_api.h b/src/gallium/drivers/swr/rasterizer/jitter/jit_api.h
index b072eb33e95..9f696697359 100644
--- a/src/gallium/drivers/swr/rasterizer/jitter/jit_api.h
+++ b/src/gallium/drivers/swr/rasterizer/jitter/jit_api.h
@@ -57,6 +57,7 @@ struct ShaderInfo;
 struct JIT_COMPILE_INPUT
 {
     SWR_SHADER_TYPE type;
+    uint32_t        crc;
 
     const void* pIR;        ///< Pointer to LLVM IR text.
     size_t irLength;
diff --git a/src/gallium/drivers/swr/rasterizer/jitter/streamout_jit.cpp b/src/gallium/drivers/swr/rasterizer/jitter/streamout_jit.cpp
index dbceb36c213..4e618f5c09f 100644
--- a/src/gallium/drivers/swr/rasterizer/jitter/streamout_jit.cpp
+++ b/src/gallium/drivers/swr/rasterizer/jitter/streamout_jit.cpp
@@ -265,8 +265,8 @@ struct StreamOutJit : public Builder
     {
         static std::size_t soNum = 0;
 
-        std::stringstream fnName("SOShader", std::ios_base::in | std::ios_base::out | std::ios_base::ate);
-        fnName << soNum++;
+        std::stringstream fnName("SO_", std::ios_base::in | std::ios_base::out | std::ios_base::ate);
+        fnName << ComputeCRC(0, &state, sizeof(state));
 
         // SO function signature
         // typedef void(__cdecl *PFN_SO_FUNC)(SWR_STREAMOUT_CONTEXT*)
@@ -278,6 +278,8 @@ struct StreamOutJit : public Builder
         FunctionType* fTy = FunctionType::get(IRB()->getVoidTy(), args, false);
         Function* soFunc = Function::Create(fTy, GlobalValue::ExternalLinkage, fnName.str(), JM()->mpCurrentModule);
 
+        soFunc->getParent()->setModuleIdentifier(soFunc->getName());
+
         // create return basic block
         BasicBlock* entry = BasicBlock::Create(JM()->mContext, "entry", soFunc);
         BasicBlock* returnBB = BasicBlock::Create(JM()->mContext, "return", soFunc);
diff --git a/src/gallium/drivers/swr/swr_state.cpp b/src/gallium/drivers/swr/swr_state.cpp
index 316872581db..2d036f91abf 100644
--- a/src/gallium/drivers/swr/swr_state.cpp
+++ b/src/gallium/drivers/swr/swr_state.cpp
@@ -495,6 +495,7 @@ swr_create_vertex_elements_state(struct pipe_context *pipe,
    assert(num_elements <= PIPE_MAX_ATTRIBS);
    velems = new swr_vertex_element_state;
    if (velems) {
+      memset(&velems->fsState, 0, sizeof(velems->fsState));
       velems->fsState.bVertexIDOffsetEnable = true;
       velems->fsState.numAttribs = num_elements;
       for (unsigned i = 0; i < num_elements; i++) {