greenplumn llvmjit_inline 源码
greenplumn llvmjit_inline 代码
文件路径：/src/backend/jit/llvm/llvmjit_inline.cpp
/*-------------------------------------------------------------------------
*
* llvmjit_inline.cpp
* Cross module inlining suitable for postgres' JIT
*
* The inliner iterates over external functions referenced from the passed
* module and attempts to inline those. It does so by utilizing pre-built
* indexes over both postgres core code and extension modules. When a match
* for an external function is found - not guaranteed! - the index will then
* be used to judge their instruction count / inline worthiness. After doing
* so for all external functions, all the referenced functions (and
* prerequisites) will be imported.
*
* Copyright (c) 2016-2019, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/backend/lib/llvmjit/llvmjit_inline.cpp
*
*-------------------------------------------------------------------------
*/
extern "C"
{
#include "postgres.h"
}
#include "jit/llvmjit.h"
extern "C"
{
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include "common/string.h"
#include "miscadmin.h"
#include "storage/fd.h"
}
#include <llvm-c/Core.h>
#include <llvm-c/BitReader.h>
/* Avoid macro clash with LLVM's C++ headers */
#undef Min
#include <llvm/ADT/SetVector.h>
#include <llvm/ADT/StringSet.h>
#include <llvm/ADT/StringMap.h>
#include <llvm/Analysis/ModuleSummaryAnalysis.h>
#if LLVM_VERSION_MAJOR > 3
#include <llvm/Bitcode/BitcodeReader.h>
#else
#include <llvm/Bitcode/ReaderWriter.h>
#include <llvm/Support/Error.h>
#endif
#include <llvm/IR/Attributes.h>
#include <llvm/IR/DebugInfo.h>
#include <llvm/IR/IntrinsicInst.h>
#include <llvm/IR/IRBuilder.h>
#include <llvm/IR/ModuleSummaryIndex.h>
#include <llvm/Linker/IRMover.h>
#include <llvm/Support/ManagedStatic.h>
/*
* Type used to represent modules InlineWorkListItem's subject is searched for
* in.
*/
typedef llvm::SmallVector<llvm::ModuleSummaryIndex *, 2> InlineSearchPath;
/*
* Item in queue of to-be-checked symbols and corresponding queue.
*/
typedef struct InlineWorkListItem
{
llvm::StringRef symbolName;
llvm::SmallVector<llvm::ModuleSummaryIndex *, 2> searchpath;
} InlineWorkListItem;
typedef llvm::SmallVector<InlineWorkListItem, 128> InlineWorkList;
/*
* Information about symbols processed during inlining. Used to prevent
* repeated searches and provide additional information.
*/
typedef struct FunctionInlineState
{
int costLimit;
bool processed;
bool inlined;
bool allowReconsidering;
} FunctionInlineState;
typedef llvm::StringMap<FunctionInlineState> FunctionInlineStates;
/*
* Map of modules that should be inlined, with a list of the to-be inlined
* symbols.
*/
typedef llvm::StringMap<llvm::StringSet<> > ImportMapTy;
const float inline_cost_decay_factor = 0.5;
const int inline_initial_cost = 150;
/*
* These are managed statics so LLVM knows to deallocate them during an
* LLVMShutdown(), rather than after (which'd cause crashes).
*/
typedef llvm::StringMap<std::unique_ptr<llvm::Module> > ModuleCache;
llvm::ManagedStatic<ModuleCache> module_cache;
typedef llvm::StringMap<std::unique_ptr<llvm::ModuleSummaryIndex> > SummaryCache;
llvm::ManagedStatic<SummaryCache> summary_cache;
static std::unique_ptr<ImportMapTy> llvm_build_inline_plan(llvm::Module *mod);
static void llvm_execute_inline_plan(llvm::Module *mod,
ImportMapTy *globalsToInline);
static llvm::Module* load_module_cached(llvm::StringRef modPath);
static std::unique_ptr<llvm::Module> load_module(llvm::StringRef Identifier);
static std::unique_ptr<llvm::ModuleSummaryIndex> llvm_load_summary(llvm::StringRef path);
static llvm::Function* create_redirection_function(std::unique_ptr<llvm::Module> &importMod,
llvm::Function *F,
llvm::StringRef Name);
static bool function_inlinable(llvm::Function &F,
int threshold,
FunctionInlineStates &functionState,
InlineWorkList &worklist,
InlineSearchPath &searchpath,
llvm::SmallPtrSet<const llvm::Function *, 8> &visitedFunctions,
int &running_instcount,
llvm::StringSet<> &importVars);
static void function_references(llvm::Function &F,
int &running_instcount,
llvm::SmallPtrSet<llvm::GlobalVariable *, 8> &referencedVars,
llvm::SmallPtrSet<llvm::Function *, 8> &referencedFunctions);
static void add_module_to_inline_search_path(InlineSearchPath& path, llvm::StringRef modpath);
static llvm::SmallVector<llvm::GlobalValueSummary *, 1>
summaries_for_guid(const InlineSearchPath& path, llvm::GlobalValue::GUID guid);
/* verbose debugging for inliner development */
/* #define INLINE_DEBUG */
#ifdef INLINE_DEBUG
#define ilog elog
#else
#define ilog(...) (void) 0
#endif
/*
* Perform inlining of external function references in M based on a simple
* cost based analysis.
*/
void
llvm_inline(LLVMModuleRef M)
{
llvm::Module *mod = llvm::unwrap(M);
std::unique_ptr<ImportMapTy> globalsToInline = llvm_build_inline_plan(mod);
if (!globalsToInline)
return;
llvm_execute_inline_plan(mod, globalsToInline.get());
}
/*
* Build information necessary for inlining external function references in
* mod.
*/
static std::unique_ptr<ImportMapTy>
llvm_build_inline_plan(llvm::Module *mod)
{
std::unique_ptr<ImportMapTy> globalsToInline(new ImportMapTy());
FunctionInlineStates functionStates;
InlineWorkList worklist;
InlineSearchPath defaultSearchPath;
/* attempt to add module to search path */
add_module_to_inline_search_path(defaultSearchPath, "$libdir/postgres");
/* if postgres isn't available, no point continuing */
if (defaultSearchPath.empty())
return nullptr;
/*
* Start inlining with current references to external functions by putting
* them on the inlining worklist. If, during inlining of those, new extern
* functions need to be inlined, they'll also be put there, with a lower
* priority.
*/
for (const llvm::Function &funcDecl : mod->functions())
{
InlineWorkListItem item = {};
FunctionInlineState inlineState = {};
/* already has a definition */
if (!funcDecl.isDeclaration())
continue;
/* llvm provides implementation */
if (funcDecl.isIntrinsic())
continue;
item.symbolName = funcDecl.getName();
item.searchpath = defaultSearchPath;
worklist.push_back(item);
inlineState.costLimit = inline_initial_cost;
inlineState.processed = false;
inlineState.inlined = false;
inlineState.allowReconsidering = false;
functionStates[funcDecl.getName()] = inlineState;
}
/*
* Iterate over pending worklist items, look them up in index, check
* whether they should be inlined.
*/
while (!worklist.empty())
{
InlineWorkListItem item = worklist.pop_back_val();
llvm::StringRef symbolName = item.symbolName;
char *cmodname;
char *cfuncname;
FunctionInlineState &inlineState = functionStates[symbolName];
llvm::GlobalValue::GUID funcGUID;
llvm_split_symbol_name(symbolName.data(), &cmodname, &cfuncname);
funcGUID = llvm::GlobalValue::getGUID(cfuncname);
/* already processed */
if (inlineState.processed)
continue;
if (cmodname)
add_module_to_inline_search_path(item.searchpath, cmodname);
/*
* Iterate over all known definitions of function, via the index. Then
* look up module(s), check if function actually is defined (there
* could be hash conflicts).
*/
for (const auto &gvs : summaries_for_guid(item.searchpath, funcGUID))
{
const llvm::FunctionSummary *fs;
llvm::StringRef modPath = gvs->modulePath();
llvm::Module *defMod;
llvm::Function *funcDef;
fs = llvm::cast<llvm::FunctionSummary>(gvs);
#if LLVM_VERSION_MAJOR > 3
if (gvs->notEligibleToImport())
{
ilog(DEBUG1, "ineligibile to import %s due to summary",
symbolName.data());
continue;
}
#endif
if ((int) fs->instCount() > inlineState.costLimit)
{
ilog(DEBUG1, "ineligibile to import %s due to early threshold: %u vs %u",
symbolName.data(), fs->instCount(), inlineState.costLimit);
inlineState.allowReconsidering = true;
continue;
}
defMod = load_module_cached(modPath);
if (defMod->materializeMetadata())
elog(FATAL, "failed to materialize metadata");
funcDef = defMod->getFunction(cfuncname);
/*
* This can happen e.g. in case of a hash collision of the
* function's name.
*/
if (!funcDef)
continue;
if (funcDef->materialize())
elog(FATAL, "failed to materialize metadata");
Assert(!funcDef->isDeclaration());
Assert(funcDef->hasExternalLinkage());
llvm::StringSet<> importVars;
llvm::SmallPtrSet<const llvm::Function *, 8> visitedFunctions;
int running_instcount = 0;
/*
* Check whether function, and objects it depends on, are
* inlinable.
*/
if (function_inlinable(*funcDef,
inlineState.costLimit,
functionStates,
worklist,
item.searchpath,
visitedFunctions,
running_instcount,
importVars))
{
/*
* Check whether function and all its dependencies are too
* big. Dependencies already counted for other functions that
* will get inlined are not counted again. While this make
* things somewhat order dependent, I can't quite see a point
* in a different behaviour.
*/
if (running_instcount > inlineState.costLimit)
{
ilog(DEBUG1, "skipping inlining of %s due to late threshold %d vs %d",
symbolName.data(), running_instcount, inlineState.costLimit);
inlineState.allowReconsidering = true;
continue;
}
ilog(DEBUG1, "inline top function %s total_instcount: %d, partial: %d",
symbolName.data(), running_instcount, fs->instCount());
/* import referenced function itself */
importVars.insert(symbolName);
{
llvm::StringSet<> &modGlobalsToInline = (*globalsToInline)[modPath];
for (auto& importVar : importVars)
modGlobalsToInline.insert(importVar.first());
Assert(modGlobalsToInline.size() > 0);
}
/* mark function as inlined */
inlineState.inlined = true;
/*
* Found definition to inline, don't look for further
* potential definitions.
*/
break;
}
else
{
ilog(DEBUG1, "had to skip inlining %s",
symbolName.data());
/* It's possible there's another definition that's inlinable. */
}
}
/*
* Signal that we're done with symbol, whether successful (inlined =
* true above) or not.
*/
inlineState.processed = true;
}
return globalsToInline;
}
/*
* Perform the actual inlining of external functions (and their dependencies)
* into mod.
*/
static void
llvm_execute_inline_plan(llvm::Module *mod, ImportMapTy *globalsToInline)
{
llvm::IRMover Mover(*mod);
for (const auto& toInline : *globalsToInline)
{
const llvm::StringRef& modPath = toInline.first();
const llvm::StringSet<>& modGlobalsToInline = toInline.second;
llvm::SetVector<llvm::GlobalValue *> GlobalsToImport;
Assert(module_cache->count(modPath));
std::unique_ptr<llvm::Module> importMod(std::move((*module_cache)[modPath]));
module_cache->erase(modPath);
if (modGlobalsToInline.empty())
continue;
for (auto &glob: modGlobalsToInline)
{
llvm::StringRef SymbolName = glob.first();
char *modname;
char *funcname;
llvm_split_symbol_name(SymbolName.data(), &modname, &funcname);
llvm::GlobalValue *valueToImport = importMod->getNamedValue(funcname);
if (!valueToImport)
elog(FATAL, "didn't refind value %s to import", SymbolName.data());
/*
* For functions (global vars are only inlined if already static),
* mark imported variables as being clones from other
* functions. That a) avoids symbol conflicts b) allows the
* optimizer to perform inlining.
*/
if (llvm::isa<llvm::Function>(valueToImport))
{
llvm::Function *F = llvm::dyn_cast<llvm::Function>(valueToImport);
typedef llvm::GlobalValue::LinkageTypes LinkageTypes;
/*
* Per-function info isn't necessarily stripped yet, as the
* module is lazy-loaded when stripped above.
*/
llvm::stripDebugInfo(*F);
/*
* If the to-be-imported function is one referenced including
* its module name, create a tiny inline function that just
* forwards the call. One might think a GlobalAlias would do
* the trick, but a) IRMover doesn't override a declaration
* with an alias pointing to a definition (instead renaming
* it), b) Aliases can't be AvailableExternally.
*/
if (modname)
{
llvm::Function *AF;
AF = create_redirection_function(importMod, F, SymbolName);
GlobalsToImport.insert(AF);
llvm::stripDebugInfo(*AF);
}
if (valueToImport->hasExternalLinkage())
{
valueToImport->setLinkage(LinkageTypes::AvailableExternallyLinkage);
}
}
GlobalsToImport.insert(valueToImport);
ilog(DEBUG1, "performing import of %s %s",
modPath.data(), SymbolName.data());
}
#if LLVM_VERSION_MAJOR > 4
#define IRMOVE_PARAMS , /*IsPerformingImport=*/false
#elif LLVM_VERSION_MAJOR > 3
#define IRMOVE_PARAMS , /*LinkModuleInlineAsm=*/false, /*IsPerformingImport=*/false
#else
#define IRMOVE_PARAMS
#endif
if (Mover.move(std::move(importMod), GlobalsToImport.getArrayRef(),
[](llvm::GlobalValue &, llvm::IRMover::ValueAdder) {}
IRMOVE_PARAMS))
elog(FATAL, "function import failed with linker error");
}
}
/*
* Return a module identified by modPath, caching it in memory.
*
* Note that such a module may *not* be modified without copying, otherwise
* the cache state would get corrupted.
*/
static llvm::Module*
load_module_cached(llvm::StringRef modPath)
{
auto it = module_cache->find(modPath);
if (it == module_cache->end())
{
it = module_cache->insert(
std::make_pair(modPath, load_module(modPath))).first;
}
return it->second.get();
}
static std::unique_ptr<llvm::Module>
load_module(llvm::StringRef Identifier)
{
LLVMMemoryBufferRef buf;
LLVMModuleRef mod;
char path[MAXPGPATH];
char *msg;
snprintf(path, MAXPGPATH,"%s/bitcode/%s", pkglib_path, Identifier.data());
if (LLVMCreateMemoryBufferWithContentsOfFile(path, &buf, &msg))
elog(FATAL, "failed to open bitcode file \"%s\": %s",
path, msg);
if (LLVMGetBitcodeModuleInContext2(LLVMGetGlobalContext(), buf, &mod))
elog(FATAL, "failed to parse bitcode in file \"%s\"", path);
/*
* Currently there's no use in more detailed debug info for JITed
* code. Until that changes, not much point in wasting memory and cycles
* on processing debuginfo.
*/
llvm::StripDebugInfo(*llvm::unwrap(mod));
return std::unique_ptr<llvm::Module>(llvm::unwrap(mod));
}
/*
* Compute list of referenced variables, functions and the instruction count
* for a function.
*/
static void
function_references(llvm::Function &F,
int &running_instcount,
llvm::SmallPtrSet<llvm::GlobalVariable *, 8> &referencedVars,
llvm::SmallPtrSet<llvm::Function *, 8> &referencedFunctions)
{
llvm::SmallPtrSet<const llvm::User *, 32> Visited;
for (llvm::BasicBlock &BB : F)
{
for (llvm::Instruction &I : BB)
{
if (llvm::isa<llvm::DbgInfoIntrinsic>(I))
continue;
llvm::SmallVector<llvm::User *, 8> Worklist;
Worklist.push_back(&I);
running_instcount++;
while (!Worklist.empty()) {
llvm::User *U = Worklist.pop_back_val();
/* visited before */
if (!Visited.insert(U).second)
continue;
for (auto &OI : U->operands()) {
llvm::User *Operand = llvm::dyn_cast<llvm::User>(OI);
if (!Operand)
continue;
if (llvm::isa<llvm::BlockAddress>(Operand))
continue;
if (auto *GV = llvm::dyn_cast<llvm::GlobalVariable>(Operand)) {
referencedVars.insert(GV);
if (GV->hasInitializer())
Worklist.push_back(GV->getInitializer());
continue;
}
if (auto *CF = llvm::dyn_cast<llvm::Function>(Operand)) {
referencedFunctions.insert(CF);
continue;
}
Worklist.push_back(Operand);
}
}
}
}
}
/*
* Check whether function F is inlinable and, if so, what globals need to be
* imported.
*
* References to external functions from, potentially recursively, inlined
* functions are added to the passed in worklist.
*/
static bool
function_inlinable(llvm::Function &F,
int threshold,
FunctionInlineStates &functionStates,
InlineWorkList &worklist,
InlineSearchPath &searchpath,
llvm::SmallPtrSet<const llvm::Function *, 8> &visitedFunctions,
int &running_instcount,
llvm::StringSet<> &importVars)
{
int subThreshold = threshold * inline_cost_decay_factor;
llvm::SmallPtrSet<llvm::GlobalVariable *, 8> referencedVars;
llvm::SmallPtrSet<llvm::Function *, 8> referencedFunctions;
/* can't rely on what may be inlined */
if (F.isInterposable())
return false;
/*
* Can't rely on function being present. Alternatively we could create a
* static version of these functions?
*/
if (F.hasAvailableExternallyLinkage())
return false;
ilog(DEBUG1, "checking inlinability of %s", F.getName().data());
if (F.materialize())
elog(FATAL, "failed to materialize metadata");
if (F.getAttributes().hasFnAttribute(llvm::Attribute::NoInline))
{
ilog(DEBUG1, "ineligibile to import %s due to noinline",
F.getName().data());
return false;
}
function_references(F, running_instcount, referencedVars, referencedFunctions);
for (llvm::GlobalVariable* rv: referencedVars)
{
if (rv->materialize())
elog(FATAL, "failed to materialize metadata");
/*
* Never want to inline externally visible vars, cheap enough to
* reference.
*/
if (rv->hasExternalLinkage() || rv->hasAvailableExternallyLinkage())
continue;
/*
* If variable is file-local, we need to inline it, to be able to
* inline the function itself. Can't do that if the variable can be
* modified, because they'd obviously get out of sync.
*
* XXX: Currently not a problem, but there'd be problems with
* nontrivial initializers if they were allowed for postgres.
*/
if (!rv->isConstant())
{
ilog(DEBUG1, "cannot inline %s due to uncloneable variable %s",
F.getName().data(), rv->getName().data());
return false;
}
ilog(DEBUG1, "memorizing global var %s linkage %d for inlining",
rv->getName().data(), (int)rv->getLinkage());
importVars.insert(rv->getName());
/* small cost attributed to each cloned global */
running_instcount += 5;
}
visitedFunctions.insert(&F);
/*
* Check referenced functions. Check whether used static ones are
* inlinable, and remember external ones for inlining.
*/
for (llvm::Function* referencedFunction: referencedFunctions)
{
llvm::StringSet<> recImportVars;
if (referencedFunction->materialize())
elog(FATAL, "failed to materialize metadata");
if (referencedFunction->isIntrinsic())
continue;
/* if already visited skip, otherwise remember */
if (!visitedFunctions.insert(referencedFunction).second)
continue;
/*
* We don't inline external functions directly here, instead we put
* them on the worklist if appropriate and check them from
* llvm_build_inline_plan().
*/
if (referencedFunction->hasExternalLinkage())
{
llvm::StringRef funcName = referencedFunction->getName();
/*
* Don't bother checking for inlining if remaining cost budget is
* very small.
*/
if (subThreshold < 5)
continue;
auto it = functionStates.find(funcName);
if (it == functionStates.end())
{
FunctionInlineState inlineState;
inlineState.costLimit = subThreshold;
inlineState.processed = false;
inlineState.inlined = false;
inlineState.allowReconsidering = false;
functionStates[funcName] = inlineState;
worklist.push_back({funcName, searchpath});
ilog(DEBUG1,
"considering extern function %s at %d for inlining",
funcName.data(), subThreshold);
}
else if (!it->second.inlined &&
(!it->second.processed || it->second.allowReconsidering) &&
it->second.costLimit < subThreshold)
{
/*
* Update inlining threshold if higher. Need to re-queue
* to be processed if already processed with lower
* threshold.
*/
if (it->second.processed)
{
ilog(DEBUG1,
"reconsidering extern function %s at %d for inlining, increasing from %d",
funcName.data(), subThreshold, it->second.costLimit);
it->second.processed = false;
it->second.allowReconsidering = false;
worklist.push_back({funcName, searchpath});
}
it->second.costLimit = subThreshold;
}
continue;
}
/* can't rely on what may be inlined */
if (referencedFunction->isInterposable())
return false;
if (!function_inlinable(*referencedFunction,
subThreshold,
functionStates,
worklist,
searchpath,
visitedFunctions,
running_instcount,
recImportVars))
{
ilog(DEBUG1,
"cannot inline %s due to required function %s not being inlinable",
F.getName().data(), referencedFunction->getName().data());
return false;
}
/* import referenced function itself */
importVars.insert(referencedFunction->getName());
/* import referenced function and its dependants */
for (auto& recImportVar : recImportVars)
importVars.insert(recImportVar.first());
}
return true;
}
/*
* Attempt to load module summary located at path. Return empty pointer when
* loading fails.
*/
static std::unique_ptr<llvm::ModuleSummaryIndex>
llvm_load_summary(llvm::StringRef path)
{
llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer> > MBOrErr =
llvm::MemoryBuffer::getFile(path);
if (std::error_code EC = MBOrErr.getError())
{
ilog(DEBUG1, "failed to open %s: %s", path.data(),
EC.message().c_str());
}
else
{
llvm::MemoryBufferRef ref(*MBOrErr.get().get());
#if LLVM_VERSION_MAJOR > 3
llvm::Expected<std::unique_ptr<llvm::ModuleSummaryIndex> > IndexOrErr =
llvm::getModuleSummaryIndex(ref);
if (IndexOrErr)
return std::move(IndexOrErr.get());
elog(FATAL, "failed to load summary \"%s\": %s",
path.data(),
toString(IndexOrErr.takeError()).c_str());
#else
llvm::ErrorOr<std::unique_ptr<llvm::ModuleSummaryIndex> > IndexOrErr =
llvm::getModuleSummaryIndex(ref, [](const llvm::DiagnosticInfo &) {});
if (IndexOrErr)
return std::move(IndexOrErr.get());
elog(FATAL, "failed to load summary \"%s\": %s",
path.data(),
IndexOrErr.getError().message().c_str());
#endif
}
return nullptr;
}
/*
* Attempt to add modpath to the search path.
*/
static void
add_module_to_inline_search_path(InlineSearchPath& searchpath, llvm::StringRef modpath)
{
/* only extension in libdir are candidates for inlining for now */
if (!modpath.startswith("$libdir/"))
return;
/* if there's no match, attempt to load */
auto it = summary_cache->find(modpath);
if (it == summary_cache->end())
{
std::string path(modpath);
path = path.replace(0, strlen("$libdir"), std::string(pkglib_path) + "/bitcode");
path += ".index.bc";
(*summary_cache)[modpath] = llvm_load_summary(path);
it = summary_cache->find(modpath);
}
Assert(it != summary_cache->end());
/* if the entry isn't NULL, it's validly loaded */
if (it->second)
searchpath.push_back(it->second.get());
}
/*
* Search for all references for functions hashing to guid in the search path,
* and return them in search path order.
*/
static llvm::SmallVector<llvm::GlobalValueSummary *, 1>
summaries_for_guid(const InlineSearchPath& path, llvm::GlobalValue::GUID guid)
{
llvm::SmallVector<llvm::GlobalValueSummary *, 1> matches;
for (auto index : path)
{
#if LLVM_VERSION_MAJOR > 4
llvm::ValueInfo funcVI = index->getValueInfo(guid);
/* if index doesn't know function, we don't have a body, continue */
if (funcVI)
for (auto &gv : funcVI.getSummaryList())
matches.push_back(gv.get());
#else
const llvm::const_gvsummary_iterator &I =
index->findGlobalValueSummaryList(guid);
if (I != index->end())
{
for (auto &gv : I->second)
matches.push_back(gv.get());
}
#endif
}
return matches;
}
/*
* Create inline wrapper with the name Name, redirecting the call to F.
*/
static llvm::Function*
create_redirection_function(std::unique_ptr<llvm::Module> &importMod,
llvm::Function *F,
llvm::StringRef Name)
{
typedef llvm::GlobalValue::LinkageTypes LinkageTypes;
llvm::LLVMContext &Context = F->getContext();
llvm::IRBuilder<> Builder(Context);
llvm::Function *AF;
llvm::BasicBlock *BB;
llvm::CallInst *fwdcall;
llvm::Attribute inlineAttribute;
AF = llvm::Function::Create(F->getFunctionType(),
LinkageTypes::AvailableExternallyLinkage,
Name, importMod.get());
BB = llvm::BasicBlock::Create(Context, "entry", AF);
Builder.SetInsertPoint(BB);
fwdcall = Builder.CreateCall(F, &*AF->arg_begin());
inlineAttribute = llvm::Attribute::get(Context,
llvm::Attribute::AlwaysInline);
fwdcall->addAttribute(~0U, inlineAttribute);
Builder.CreateRet(fwdcall);
return AF;
}
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