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llvm-ptls.cpp
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llvm-ptls.cpp
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// This file is a part of Julia. License is MIT: http:https://julialang.org/license
#define DEBUG_TYPE "lower_ptls"
#undef DEBUG
// LLVM pass to optimize TLS access and remove references to julia intrinsics
#include "llvm-version.h"
#include "support/dtypes.h"
#include <sstream>
#include <llvm/Pass.h>
#include <llvm/IR/Module.h>
#include <llvm/IR/Function.h>
#include <llvm/IR/Instructions.h>
#include <llvm/IR/Constants.h>
#include <llvm/IR/LLVMContext.h>
#include <llvm/IR/LegacyPassManager.h>
#include <llvm/IR/MDBuilder.h>
#include "julia.h"
#include "julia_internal.h"
#if JL_LLVM_VERSION >= 30700 && defined(JULIA_ENABLE_THREADING)
# include <llvm/IR/InlineAsm.h>
#endif
using namespace llvm;
extern MDNode *tbaa_make_child(const char *name, MDNode *parent, bool isConstant=false);
namespace {
struct LowerPTLS: public ModulePass {
static char ID;
LowerPTLS(bool _imaging_mode=false)
: ModulePass(ID),
imaging_mode(_imaging_mode)
{}
private:
bool imaging_mode;
bool runOnModule(Module &M) override;
void runOnFunction(LLVMContext &ctx, Module &M, Function *F,
Function *ptls_getter, Type *T_ppjlvalue, MDNode *tbaa_const);
};
static void ensure_global(const char *name, Type *t, Module &M,
bool dllimport=false)
{
if (M.getNamedValue(name))
return;
GlobalVariable *proto = new GlobalVariable(M, t, false,
GlobalVariable::ExternalLinkage,
NULL, name);
#ifdef _OS_WINDOWS_
// setting JL_DLLEXPORT correctly only matters when building a binary
// (global_proto will strip this from the JIT)
if (dllimport) {
#if JL_LLVM_VERSION >= 30500
// add the __declspec(dllimport) attribute
proto->setDLLStorageClass(GlobalValue::DLLImportStorageClass);
#else
proto->setLinkage(GlobalValue::DLLImportLinkage);
#endif
}
#else // _OS_WINDOWS_
(void)proto;
#endif // _OS_WINDOWS_
}
void LowerPTLS::runOnFunction(LLVMContext &ctx, Module &M, Function *F,
Function *ptls_getter, Type *T_ppjlvalue, MDNode *tbaa_const)
{
CallInst *ptlsStates = NULL;
for (auto I = F->getEntryBlock().begin(), E = F->getEntryBlock().end();
I != E; ++I) {
if (CallInst *callInst = dyn_cast<CallInst>(&*I)) {
if (callInst->getCalledValue() == ptls_getter) {
ptlsStates = callInst;
break;
}
}
}
if (!ptlsStates)
return;
if (ptlsStates->use_empty()) {
ptlsStates->eraseFromParent();
return;
}
#ifdef JULIA_ENABLE_THREADING
if (imaging_mode) {
GlobalVariable *GV = cast<GlobalVariable>(
M.getNamedValue("jl_get_ptls_states.ptr"));
LoadInst *getter = new LoadInst(GV, "", ptlsStates);
getter->setMetadata(llvm::LLVMContext::MD_tbaa, tbaa_const);
ptlsStates->setCalledFunction(getter);
ptlsStates->addAttribute(AttributeSet::FunctionIndex,
Attribute::ReadNone);
ptlsStates->addAttribute(AttributeSet::FunctionIndex,
Attribute::NoUnwind);
}
#if JL_LLVM_VERSION >= 30700
else if (jl_tls_offset != -1) {
auto T_int8 = Type::getInt8Ty(ctx);
auto T_pint8 = PointerType::get(T_int8, 0);
// Replace the function call with inline assembly if we know
// how to generate it.
# if defined(_CPU_X86_64_) || defined(_CPU_X86_)
// Workaround LLVM bug by hiding the offset computation
// (and therefore the optimization opportunity) from LLVM.
static const std::string asm_str = [&] () {
std::stringstream stm;
# if defined(_CPU_X86_64_)
stm << "movq %fs:0, $0;\naddq $$" << jl_tls_offset << ", $0";
# else
stm << "movl %gs:0, $0;\naddl $$" << jl_tls_offset << ", $0";
# endif
return stm.str();
}();
// The add instruction clobbers flags
auto tp = InlineAsm::get(FunctionType::get(T_pint8, false),
asm_str.c_str(),
"=r,~{dirflag},~{fpsr},~{flags}", false);
Value *tls = CallInst::Create(tp, "ptls_i8", ptlsStates);
tls = new BitCastInst(tls, PointerType::get(T_ppjlvalue, 0),
"ptls", ptlsStates);
# elif defined(_CPU_AARCH64_)
// AArch64 doesn't seem to have this issue.
// (Possibly because there are many more registers and the offset is
// positive and small)
// It's also harder to emit the offset in a generic way on AArch64
// (need to generate one or two `add` with shift) so let llvm emit
// the add for now.
auto T_size = (sizeof(size_t) == 8 ? Type::getInt64Ty(ctx) :
Type::getInt32Ty(ctx));
const char *asm_str = "mrs $0, tpidr_el0";
auto offset = ConstantInt::getSigned(T_size, jl_tls_offset);
auto tp = InlineAsm::get(FunctionType::get(T_pint8, false),
asm_str, "=r", false);
Value *tls = CallInst::Create(tp, "thread_ptr", ptlsStates);
tls = GetElementPtrInst::Create(T_int8, tls, {offset},
"ptls_i8", ptlsStates);
tls = new BitCastInst(tls, PointerType::get(T_ppjlvalue, 0),
"ptls", ptlsStates);
# else
Value *tls = nullptr;
assert(0 && "Cannot emit thread pointer for this architecture.");
# endif
(void)T_pint8;
ptlsStates->replaceAllUsesWith(tls);
ptlsStates->eraseFromParent();
}
#endif
else {
ptlsStates->addAttribute(AttributeSet::FunctionIndex,
Attribute::ReadNone);
ptlsStates->addAttribute(AttributeSet::FunctionIndex,
Attribute::NoUnwind);
}
#else
ptlsStates->replaceAllUsesWith(M.getNamedValue("jl_tls_states"));
ptlsStates->eraseFromParent();
#endif
}
bool LowerPTLS::runOnModule(Module &M)
{
MDBuilder mbuilder(M.getContext());
MDNode *tbaa_root = mbuilder.createTBAARoot("jtbaa");
MDNode *tbaa_const = tbaa_make_child("jtbaa_const", tbaa_root, true);
Function *ptls_getter = M.getFunction("jl_get_ptls_states");
if (!ptls_getter)
return true;
LLVMContext &ctx = M.getContext();
FunctionType *functype = ptls_getter->getFunctionType();
auto T_ppjlvalue =
cast<PointerType>(functype->getReturnType())->getElementType();
#ifdef JULIA_ENABLE_THREADING
if (imaging_mode)
ensure_global("jl_get_ptls_states.ptr", functype->getPointerTo(), M);
#else
ensure_global("jl_tls_states", T_ppjlvalue, M, imaging_mode);
#endif
for (auto F = M.begin(), E = M.end(); F != E; ++F) {
if (F->isDeclaration())
continue;
runOnFunction(ctx, M, &*F, ptls_getter, T_ppjlvalue, tbaa_const);
}
#ifndef JULIA_ENABLE_THREADING
ptls_getter->eraseFromParent();
#endif
return true;
}
char LowerPTLS::ID = 0;
static RegisterPass<LowerPTLS> X("LowerPTLS", "LowerPTLS Pass",
false /* Only looks at CFG */,
false /* Analysis Pass */);
} // anonymous namespace
Pass *createLowerPTLSPass(bool imaging_mode)
{
return new LowerPTLS(imaging_mode);
}
extern "C" JL_DLLEXPORT
void LLVMAddLowerPTLSPass(LLVMPassManagerRef PM, int imaging_mode) {
unwrap(PM)->add(createLowerPTLSPass(imaging_mode != 0));
}