Revision 52764a70462f2c0499c982a97e2bb134185aba52 authored by Jameson Nash on 01 August 2018, 02:13:14 UTC, committed by Jameson Nash on 01 August 2018, 21:43:56 UTC
1 parent 8d343d8
llvm-ptls.cpp
// This file is a part of Julia. License is MIT: https://julialang.org/license
#define DEBUG_TYPE "lower_ptls"
#undef DEBUG
// LLVM pass to lower 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/MDBuilder.h>
#if defined(JULIA_ENABLE_THREADING)
# include <llvm/IR/InlineAsm.h>
# include <llvm/Transforms/Utils/BasicBlockUtils.h>
#endif
#include "julia.h"
#include "julia_internal.h"
#include "codegen_shared.h"
#include "julia_assert.h"
using namespace llvm;
std::pair<MDNode*,MDNode*> tbaa_make_child(const char *name, MDNode *parent=nullptr,
bool isConstant=false);
namespace {
struct LowerPTLS: public ModulePass {
static char ID;
LowerPTLS(bool imaging_mode=false)
: ModulePass(ID),
imaging_mode(imaging_mode)
{}
private:
const bool imaging_mode;
Module *M;
Function *ptls_getter;
LLVMContext *ctx;
MDNode *tbaa_const;
PointerType *T_ptls_getter;
PointerType *T_ppjlvalue;
PointerType *T_pppjlvalue;
Type *T_int8;
Type *T_size;
PointerType *T_pint8;
#ifdef JULIA_ENABLE_THREADING
GlobalVariable *ptls_slot{nullptr};
GlobalVariable *ptls_offset{nullptr};
void set_ptls_attrs(CallInst *ptlsStates) const;
Instruction *emit_ptls_tp(Value *offset, Instruction *insertBefore) const;
template<typename T> T *add_comdat(T *G) const;
GlobalVariable *create_aliased_global(Type *T, StringRef name) const;
#else
GlobalVariable *static_tls;
#endif
void fix_ptls_use(CallInst *ptlsStates);
bool runOnModule(Module &M) override;
};
#ifdef JULIA_ENABLE_THREADING
void LowerPTLS::set_ptls_attrs(CallInst *ptlsStates) const
{
#if JL_LLVM_VERSION >= 50000
ptlsStates->addAttribute(AttributeList::FunctionIndex, Attribute::ReadNone);
ptlsStates->addAttribute(AttributeList::FunctionIndex, Attribute::NoUnwind);
#else
ptlsStates->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadNone);
ptlsStates->addAttribute(AttributeSet::FunctionIndex, Attribute::NoUnwind);
#endif
}
Instruction *LowerPTLS::emit_ptls_tp(Value *offset, Instruction *insertBefore) const
{
#if defined(_CPU_X86_64_) || defined(_CPU_X86_)
if (insertBefore->getFunction()->callsFunctionThatReturnsTwice()) {
// Workaround LLVM bug by hiding the offset computation
// (and therefore the optimization opportunity) from LLVM.
// Ref https://github.com/JuliaLang/julia/issues/17288
static const std::string const_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();
}();
# if defined(_CPU_X86_64_)
const char *dyn_asm_str = "movq %fs:0, $0;\naddq $1, $0";
# else
const char *dyn_asm_str = "movl %gs:0, $0;\naddl $1, $0";
# endif
// The add instruction clobbers flags
Value *tls;
if (offset) {
std::vector<Type*> args(0);
args.push_back(offset->getType());
auto tp = InlineAsm::get(FunctionType::get(T_pint8, args, false),
dyn_asm_str, "=&r,r,~{dirflag},~{fpsr},~{flags}", false);
tls = CallInst::Create(tp, offset, "ptls_i8", insertBefore);
}
else {
auto tp = InlineAsm::get(FunctionType::get(T_pint8, false),
const_asm_str.c_str(), "=r,~{dirflag},~{fpsr},~{flags}",
false);
tls = CallInst::Create(tp, "ptls_i8", insertBefore);
}
return new BitCastInst(tls, T_pppjlvalue, "ptls", insertBefore);
}
#endif
// AArch64/ARM 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 ARM/AArch64
// (need to generate one or two `add` with shift) so let llvm emit
// the add for now.
#if defined(_CPU_AARCH64_)
const char *asm_str = "mrs $0, tpidr_el0";
#elif defined(__ARM_ARCH) && __ARM_ARCH >= 7
const char *asm_str = "mrc p15, 0, $0, c13, c0, 3";
#elif defined(_CPU_X86_64_)
const char *asm_str = "movq %fs:0, $0";
#elif defined(_CPU_X86_)
const char *asm_str = "movl %gs:0, $0";
#else
const char *asm_str = nullptr;
assert(0 && "Cannot emit thread pointer for this architecture.");
#endif
if (!offset)
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", insertBefore);
tls = GetElementPtrInst::Create(T_int8, tls, {offset}, "ptls_i8", insertBefore);
return new BitCastInst(tls, T_pppjlvalue, "ptls", insertBefore);
}
GlobalVariable *LowerPTLS::create_aliased_global(Type *T, StringRef name) const
{
// Create a static global variable and points a global alias to it so that
// the address is visible externally but LLVM can still assume that the
// address of this variable doesn't need dynamic relocation
// (can be accessed with a single PC-rel load).
auto GV = new GlobalVariable(*M, T, false, GlobalVariable::InternalLinkage,
Constant::getNullValue(T), name + ".real");
add_comdat(GlobalAlias::create(T, 0, GlobalVariable::ExternalLinkage,
name, GV, M));
return GV;
}
template<typename T>
inline T *LowerPTLS::add_comdat(T *G) const
{
#if defined(_OS_WINDOWS_)
// Add comdat information to make MSVC link.exe happy
// it's valid to emit this for ld.exe too,
// but makes it very slow to link for no benefit
#if defined(_COMPILER_MICROSOFT_)
Comdat *jl_Comdat = G->getParent()->getOrInsertComdat(G->getName());
// ELF only supports Comdat::Any
jl_Comdat->setSelectionKind(Comdat::NoDuplicates);
G->setComdat(jl_Comdat);
#endif
// add __declspec(dllexport) to everything marked for export
if (G->getLinkage() == GlobalValue::ExternalLinkage)
G->setDLLStorageClass(GlobalValue::DLLExportStorageClass);
else
G->setDLLStorageClass(GlobalValue::DefaultStorageClass);
#endif
return G;
}
#endif
void LowerPTLS::fix_ptls_use(CallInst *ptlsStates)
{
if (ptlsStates->use_empty()) {
ptlsStates->eraseFromParent();
return;
}
#ifdef JULIA_ENABLE_THREADING
if (imaging_mode) {
if (jl_tls_elf_support) {
// if (offset != 0)
// ptls = tp + offset;
// else
// ptls = getter();
auto offset = new LoadInst(T_size, ptls_offset, "", false, ptlsStates);
offset->setMetadata(llvm::LLVMContext::MD_tbaa, tbaa_const);
offset->setMetadata(llvm::LLVMContext::MD_invariant_load, MDNode::get(*ctx, None));
auto cmp = new ICmpInst(ptlsStates, CmpInst::ICMP_NE, offset,
Constant::getNullValue(offset->getType()));
MDBuilder MDB(*ctx);
SmallVector<uint32_t, 2> Weights{9, 1};
TerminatorInst *fastTerm;
TerminatorInst *slowTerm;
SplitBlockAndInsertIfThenElse(cmp, ptlsStates, &fastTerm, &slowTerm,
MDB.createBranchWeights(Weights));
auto fastTLS = emit_ptls_tp(offset, fastTerm);
auto phi = PHINode::Create(T_pppjlvalue, 2, "", ptlsStates);
ptlsStates->replaceAllUsesWith(phi);
ptlsStates->moveBefore(slowTerm);
auto getter = new LoadInst(T_ptls_getter, ptls_slot, "", false, ptlsStates);
getter->setMetadata(llvm::LLVMContext::MD_tbaa, tbaa_const);
getter->setMetadata(llvm::LLVMContext::MD_invariant_load, MDNode::get(*ctx, None));
ptlsStates->setCalledFunction(getter);
set_ptls_attrs(ptlsStates);
phi->addIncoming(fastTLS, fastTLS->getParent());
phi->addIncoming(ptlsStates, ptlsStates->getParent());
return;
}
// In imaging mode, we emit the function address as a load of a static
// variable to be filled (in `staticdata.c`) at initialization time of the sysimg.
// This way we can by pass the extra indirection in `jl_get_ptls_states`
// since we may not know which getter function to use ahead of time.
auto getter = new LoadInst(T_ptls_getter, ptls_slot, "", false, ptlsStates);
getter->setMetadata(llvm::LLVMContext::MD_tbaa, tbaa_const);
getter->setMetadata(llvm::LLVMContext::MD_invariant_load, MDNode::get(*ctx, None));
ptlsStates->setCalledFunction(getter);
set_ptls_attrs(ptlsStates);
}
else if (jl_tls_offset != -1) {
ptlsStates->replaceAllUsesWith(emit_ptls_tp(nullptr, ptlsStates));
ptlsStates->eraseFromParent();
}
else {
// use the address of the actual getter function directly
auto val = ConstantInt::get(T_size, (uintptr_t)jl_get_ptls_states_getter());
ptlsStates->setCalledFunction(ConstantExpr::getIntToPtr(val, T_ptls_getter));
set_ptls_attrs(ptlsStates);
}
#else
ptlsStates->replaceAllUsesWith(static_tls);
ptlsStates->eraseFromParent();
#endif
}
bool LowerPTLS::runOnModule(Module &_M)
{
M = &_M;
ptls_getter = M->getFunction("julia.ptls_states");
if (!ptls_getter)
return false;
ctx = &M->getContext();
tbaa_const = tbaa_make_child("jtbaa_const", nullptr, true).first;
auto FT_ptls_getter = ptls_getter->getFunctionType();
T_ptls_getter = FT_ptls_getter->getPointerTo();
T_pppjlvalue = cast<PointerType>(FT_ptls_getter->getReturnType());
T_ppjlvalue = cast<PointerType>(T_pppjlvalue->getElementType());
T_int8 = Type::getInt8Ty(*ctx);
T_size = sizeof(size_t) == 8 ? Type::getInt64Ty(*ctx) : Type::getInt32Ty(*ctx);
T_pint8 = T_int8->getPointerTo();
#ifdef JULIA_ENABLE_THREADING
if (imaging_mode) {
ptls_slot = create_aliased_global(T_ptls_getter, "jl_get_ptls_states_slot");
ptls_offset = create_aliased_global(T_size, "jl_tls_offset");
}
#else
static_tls = new GlobalVariable(*M, T_ppjlvalue, false, GlobalVariable::ExternalLinkage,
NULL, "jl_tls_states");
#endif
for (auto it = ptls_getter->user_begin(); it != ptls_getter->user_end();) {
auto call = cast<CallInst>(*it);
++it;
assert(call->getCalledValue() == ptls_getter);
fix_ptls_use(call);
}
assert(ptls_getter->use_empty());
ptls_getter->eraseFromParent();
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);
}
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