Revision 96b96c8d5195b968656e786ded8f6a1a96168427 authored by Jishnu Bhattacharya on 20 March 2024, 18:20:09 UTC, committed by Jishnu Bhattacharya on 20 March 2024, 18:20:09 UTC
1 parent bc7ba3d
llvm-ptls.cpp
// This file is a part of Julia. License is MIT: https://julialang.org/license
// LLVM pass to lower TLS access and remove references to julia intrinsics
#include "llvm-version.h"
#include "support/dtypes.h"
#include "passes.h"
#include <llvm-c/Core.h>
#include <llvm-c/Types.h>
#include <llvm/Pass.h>
#include <llvm/ADT/Triple.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>
#include <llvm/IR/Verifier.h>
#include <llvm/IR/InlineAsm.h>
#include <llvm/Transforms/Utils/BasicBlockUtils.h>
#include "julia.h"
#include "julia_internal.h"
#include "llvm-codegen-shared.h"
#include "julia_assert.h"
#define DEBUG_TYPE "lower_ptls"
#undef DEBUG
using namespace llvm;
typedef Instruction TerminatorInst;
namespace {
struct LowerPTLS {
LowerPTLS(Module &M, bool imaging_mode=false)
: imaging_mode(imaging_mode), M(&M), TargetTriple(M.getTargetTriple())
{}
bool run(bool *CFGModified);
private:
const bool imaging_mode;
Module *M;
Triple TargetTriple;
MDNode *tbaa_const{nullptr};
MDNode *tbaa_gcframe{nullptr};
FunctionType *FT_pgcstack_getter{nullptr};
PointerType *T_pgcstack_getter{nullptr};
PointerType *T_pppjlvalue{nullptr};
Type *T_size{nullptr};
GlobalVariable *pgcstack_func_slot{nullptr};
GlobalVariable *pgcstack_key_slot{nullptr};
GlobalVariable *pgcstack_offset{nullptr};
void set_pgcstack_attrs(CallInst *pgcstack) const;
Instruction *emit_pgcstack_tp(Value *offset, Instruction *insertBefore) const;
template<typename T> T *add_comdat(T *G) const;
GlobalVariable *create_hidden_global(Type *T, StringRef name) const;
void fix_pgcstack_use(CallInst *pgcstack, Function *pgcstack_getter, bool or_new, bool *CFGModified);
};
void LowerPTLS::set_pgcstack_attrs(CallInst *pgcstack) const
{
#if JL_LLVM_VERSION >= 160000
pgcstack->addFnAttr(Attribute::getWithMemoryEffects(pgcstack->getContext(), MemoryEffects::none()));
#else
addFnAttr(pgcstack, Attribute::ReadNone);
#endif
addFnAttr(pgcstack, Attribute::NoUnwind);
}
Instruction *LowerPTLS::emit_pgcstack_tp(Value *offset, Instruction *insertBefore) const
{
IRBuilder<> builder(insertBefore);
Value *tls;
if (TargetTriple.isX86() && 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
std::string const_asm_str;
raw_string_ostream(const_asm_str) << (TargetTriple.getArch() == Triple::x86_64 ?
"movq %fs:0, $0;\naddq $$" : "movl %gs:0, $0;\naddl $$")
<< jl_tls_offset << ", $0";
const char *dyn_asm_str = TargetTriple.getArch() == Triple::x86_64 ?
"movq %fs:0, $0;\naddq $1, $0" :
"movl %gs:0, $0;\naddl $1, $0";
// The add instruction clobbers flags
if (offset) {
SmallVector<Type*, 0> args(0);
args.push_back(offset->getType());
auto tp = InlineAsm::get(FunctionType::get(Type::getInt8PtrTy(builder.getContext()), args, false),
dyn_asm_str, "=&r,r,~{dirflag},~{fpsr},~{flags}", false);
tls = builder.CreateCall(tp, {offset}, "pgcstack");
}
else {
auto tp = InlineAsm::get(FunctionType::get(Type::getInt8PtrTy(insertBefore->getContext()), false),
const_asm_str.c_str(), "=r,~{dirflag},~{fpsr},~{flags}",
false);
tls = builder.CreateCall(tp, {}, "tls_pgcstack");
}
} else {
// 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.
const char *asm_str;
if (TargetTriple.isAArch64()) {
asm_str = "mrs $0, tpidr_el0";
} else if (TargetTriple.isARM()) {
asm_str = "mrc p15, 0, $0, c13, c0, 3";
} else if (TargetTriple.getArch() == Triple::x86_64) {
asm_str = "movq %fs:0, $0";
} else if (TargetTriple.getArch() == Triple::x86) {
asm_str = "movl %gs:0, $0";
} else {
llvm_unreachable("Cannot emit thread pointer for this architecture.");
}
if (!offset)
offset = ConstantInt::getSigned(T_size, jl_tls_offset);
auto tp = InlineAsm::get(FunctionType::get(Type::getInt8PtrTy(builder.getContext()), false), asm_str, "=r", false);
tls = builder.CreateCall(tp, {}, "thread_ptr");
tls = builder.CreateGEP(Type::getInt8Ty(builder.getContext()), tls, {offset}, "tls_ppgcstack");
}
tls = builder.CreateBitCast(tls, T_pppjlvalue->getPointerTo());
return builder.CreateLoad(T_pppjlvalue, tls, "tls_pgcstack");
}
GlobalVariable *LowerPTLS::create_hidden_global(Type *T, StringRef name) const
{
auto GV = new GlobalVariable(*M, T, false, GlobalVariable::ExternalLinkage,
nullptr, name);
GV->setVisibility(GlobalValue::HiddenVisibility);
GV->setDSOLocal(true);
return GV;
}
void LowerPTLS::fix_pgcstack_use(CallInst *pgcstack, Function *pgcstack_getter, bool or_new, bool *CFGModified)
{
if (pgcstack->use_empty()) {
pgcstack->eraseFromParent();
return;
}
if (or_new) {
// pgcstack();
// if (pgcstack != nullptr)
// last_gc_state = emit_gc_unsafe_enter(ctx);
// phi = pgcstack; // fast
// else
// last_gc_state = gc_safe;
// phi = adopt(); // slow
// use phi;
// if (!retboxed)
// foreach(retinst)
// emit_gc_unsafe_leave(ctx, last_gc_state);
IRBuilder<> builder(pgcstack->getNextNode());
auto phi = builder.CreatePHI(pgcstack->getType(), 2, "pgcstack");
pgcstack->replaceAllUsesWith(phi);
MDBuilder MDB(pgcstack->getContext());
SmallVector<uint32_t, 2> Weights{9, 1};
TerminatorInst *fastTerm;
TerminatorInst *slowTerm;
assert(pgcstack->getType()); // Static analyzer
builder.SetInsertPoint(phi);
auto cmp = builder.CreateICmpNE(pgcstack, Constant::getNullValue(pgcstack->getType()));
SplitBlockAndInsertIfThenElse(cmp, phi, &fastTerm, &slowTerm,
MDB.createBranchWeights(Weights));
if (CFGModified)
*CFGModified = true;
// emit slow branch code
CallInst *adopt = cast<CallInst>(pgcstack->clone());
Function *adoptFunc = M->getFunction(XSTR(jl_adopt_thread));
if (adoptFunc == NULL) {
adoptFunc = Function::Create(pgcstack_getter->getFunctionType(),
pgcstack_getter->getLinkage(), pgcstack_getter->getAddressSpace(),
XSTR(jl_adopt_thread), M);
adoptFunc->copyAttributesFrom(pgcstack_getter);
adoptFunc->copyMetadata(pgcstack_getter, 0);
}
adopt->setCalledFunction(adoptFunc);
adopt->insertBefore(slowTerm);
phi->addIncoming(adopt, slowTerm->getParent());
// emit fast branch code
builder.SetInsertPoint(fastTerm->getParent());
fastTerm->removeFromParent();
MDNode *tbaa = tbaa_gcframe;
Value *prior = emit_gc_unsafe_enter(builder, T_size, get_current_ptls_from_task(builder, T_size, get_current_task_from_pgcstack(builder, T_size, pgcstack), tbaa), true);
builder.Insert(fastTerm);
phi->addIncoming(pgcstack, fastTerm->getParent());
// emit pre-return cleanup
if (CountTrackedPointers(pgcstack->getParent()->getParent()->getReturnType()).count == 0) {
auto last_gc_state = PHINode::Create(Type::getInt8Ty(pgcstack->getContext()), 2, "", phi);
// if we called jl_adopt_thread, we must end this cfunction back in the safe-state
last_gc_state->addIncoming(ConstantInt::get(Type::getInt8Ty(M->getContext()), JL_GC_STATE_SAFE), slowTerm->getParent());
last_gc_state->addIncoming(prior, fastTerm->getParent());
for (auto &BB : *pgcstack->getParent()->getParent()) {
if (isa<ReturnInst>(BB.getTerminator())) {
builder.SetInsertPoint(BB.getTerminator());
emit_gc_unsafe_leave(builder, T_size, get_current_ptls_from_task(builder, T_size, get_current_task_from_pgcstack(builder, T_size, phi), tbaa), last_gc_state, true);
}
}
}
}
if (imaging_mode) {
IRBuilder<> builder(pgcstack);
if (jl_tls_elf_support) {
// if (offset != 0)
// pgcstack = tp + offset; // fast
// else
// pgcstack = getter(); // slow
auto offset = builder.CreateLoad(T_size, pgcstack_offset);
offset->setMetadata(llvm::LLVMContext::MD_tbaa, tbaa_const);
offset->setMetadata(llvm::LLVMContext::MD_invariant_load, MDNode::get(pgcstack->getContext(), None));
auto cmp = builder.CreateICmpNE(offset, Constant::getNullValue(offset->getType()));
MDBuilder MDB(pgcstack->getContext());
SmallVector<uint32_t, 2> Weights{9, 1};
TerminatorInst *fastTerm;
TerminatorInst *slowTerm;
SplitBlockAndInsertIfThenElse(cmp, pgcstack, &fastTerm, &slowTerm,
MDB.createBranchWeights(Weights));
if (CFGModified)
*CFGModified = true;
auto fastTLS = emit_pgcstack_tp(offset, fastTerm);
// refresh the basic block in the builder
builder.SetInsertPoint(pgcstack);
auto phi = builder.CreatePHI(T_pppjlvalue, 2, "pgcstack");
pgcstack->replaceAllUsesWith(phi);
pgcstack->moveBefore(slowTerm);
// refresh the basic block in the builder
builder.SetInsertPoint(pgcstack);
auto getter = builder.CreateLoad(T_pgcstack_getter, pgcstack_func_slot);
getter->setMetadata(llvm::LLVMContext::MD_tbaa, tbaa_const);
getter->setMetadata(llvm::LLVMContext::MD_invariant_load, MDNode::get(pgcstack->getContext(), None));
pgcstack->setCalledFunction(pgcstack->getFunctionType(), getter);
set_pgcstack_attrs(pgcstack);
phi->addIncoming(fastTLS, fastTLS->getParent());
phi->addIncoming(pgcstack, pgcstack->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 bypass the extra indirection in `jl_get_pgcstack`
// since we may not know which getter function to use ahead of time.
auto getter = builder.CreateLoad(T_pgcstack_getter, pgcstack_func_slot);
getter->setMetadata(llvm::LLVMContext::MD_tbaa, tbaa_const);
getter->setMetadata(llvm::LLVMContext::MD_invariant_load, MDNode::get(pgcstack->getContext(), None));
if (TargetTriple.isOSDarwin()) {
auto key = builder.CreateLoad(T_size, pgcstack_key_slot);
key->setMetadata(llvm::LLVMContext::MD_tbaa, tbaa_const);
key->setMetadata(llvm::LLVMContext::MD_invariant_load, MDNode::get(pgcstack->getContext(), None));
auto new_pgcstack = builder.CreateCall(FT_pgcstack_getter, getter, {key});
new_pgcstack->takeName(pgcstack);
pgcstack->replaceAllUsesWith(new_pgcstack);
pgcstack->eraseFromParent();
pgcstack = new_pgcstack;
} else {
pgcstack->setCalledFunction(pgcstack->getFunctionType(), getter);
}
set_pgcstack_attrs(pgcstack);
}
else if (jl_tls_offset != -1) {
pgcstack->replaceAllUsesWith(emit_pgcstack_tp(nullptr, pgcstack));
pgcstack->eraseFromParent();
}
else {
// use the address of the actual getter function directly
jl_get_pgcstack_func *f;
jl_pgcstack_key_t k;
jl_pgcstack_getkey(&f, &k);
Constant *val = ConstantInt::get(T_size, (uintptr_t)f);
val = ConstantExpr::getIntToPtr(val, T_pgcstack_getter);
if (TargetTriple.isOSDarwin()) {
assert(sizeof(k) == sizeof(uintptr_t));
Constant *key = ConstantInt::get(T_size, (uintptr_t)k);
auto new_pgcstack = CallInst::Create(FT_pgcstack_getter, val, {key}, "", pgcstack);
new_pgcstack->takeName(pgcstack);
pgcstack->replaceAllUsesWith(new_pgcstack);
pgcstack->eraseFromParent();
pgcstack = new_pgcstack;
} else {
pgcstack->setCalledFunction(pgcstack->getFunctionType(), val);
}
set_pgcstack_attrs(pgcstack);
}
}
bool LowerPTLS::run(bool *CFGModified)
{
bool need_init = true;
auto runOnGetter = [&](bool or_new) {
Function *pgcstack_getter = M->getFunction(or_new ? "julia.get_pgcstack_or_new" : "julia.get_pgcstack");
if (!pgcstack_getter)
return false;
if (need_init) {
tbaa_const = tbaa_make_child_with_context(M->getContext(), "jtbaa_const", nullptr, true).first;
tbaa_gcframe = tbaa_make_child_with_context(M->getContext(), "jtbaa_gcframe").first;
T_size = M->getDataLayout().getIntPtrType(M->getContext());
FT_pgcstack_getter = pgcstack_getter->getFunctionType();
if (TargetTriple.isOSDarwin()) {
assert(sizeof(jl_pgcstack_key_t) == sizeof(uintptr_t));
FT_pgcstack_getter = FunctionType::get(FT_pgcstack_getter->getReturnType(), {T_size}, false);
}
T_pgcstack_getter = FT_pgcstack_getter->getPointerTo();
T_pppjlvalue = cast<PointerType>(FT_pgcstack_getter->getReturnType());
if (imaging_mode) {
pgcstack_func_slot = create_hidden_global(T_pgcstack_getter, "jl_pgcstack_func_slot");
pgcstack_key_slot = create_hidden_global(T_size, "jl_pgcstack_key_slot"); // >= sizeof(jl_pgcstack_key_t)
pgcstack_offset = create_hidden_global(T_size, "jl_tls_offset");
}
need_init = false;
}
for (auto it = pgcstack_getter->user_begin(); it != pgcstack_getter->user_end();) {
auto call = cast<CallInst>(*it);
++it;
auto f = call->getCaller();
Value *pgcstack = NULL;
for (Function::arg_iterator arg = f->arg_begin(); arg != f->arg_end();++arg) {
if (arg->hasSwiftSelfAttr()){
pgcstack = &*arg;
break;
}
}
if (pgcstack) {
pgcstack->takeName(call);
call->replaceAllUsesWith(pgcstack);
call->eraseFromParent();
continue;
}
assert(call->getCalledOperand() == pgcstack_getter);
fix_pgcstack_use(call, pgcstack_getter, or_new, CFGModified);
}
assert(pgcstack_getter->use_empty());
pgcstack_getter->eraseFromParent();
return true;
};
return runOnGetter(false) + runOnGetter(true);
}
} // anonymous namespace
PreservedAnalyses LowerPTLSPass::run(Module &M, ModuleAnalysisManager &AM) {
LowerPTLS lower(M, imaging_mode);
bool CFGModified = false;
bool modified = lower.run(&CFGModified);
#ifdef JL_VERIFY_PASSES
assert(!verifyLLVMIR(M));
#endif
if (modified) {
if (CFGModified) {
return PreservedAnalyses::none();
} else {
return PreservedAnalyses::allInSet<CFGAnalyses>();
}
}
return PreservedAnalyses::all();
}
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