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llvm-multiversioning.cpp
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llvm-multiversioning.cpp
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// This file is a part of Julia. License is MIT: https://julialang.org/license
// Function multi-versioning
// LLVM pass to clone function for different archs
#include "llvm-version.h"
#include "passes.h"
#include <llvm-c/Core.h>
#include <llvm-c/Types.h>
#include <llvm/Pass.h>
#include <llvm/ADT/Statistic.h>
#include <llvm/IR/Module.h>
#include <llvm/IR/LegacyPassManager.h>
#include <llvm/IR/Function.h>
#include <llvm/IR/Instructions.h>
#include <llvm/IR/Constants.h>
#include <llvm/IR/LLVMContext.h>
#include <llvm/Analysis/LoopInfo.h>
#include <llvm/Analysis/CallGraph.h>
#include <llvm/IR/LegacyPassManager.h>
#include <llvm/IR/IRBuilder.h>
#include <llvm/IR/DebugInfoMetadata.h>
#include <llvm/IR/Verifier.h>
#include <llvm/Transforms/Utils/Cloning.h>
#include "julia.h"
#include "julia_internal.h"
#include "processor.h"
#include "support/dtypes.h"
#include <map>
#include <memory>
#include <set>
#include <vector>
#include "llvm-codegen-shared.h"
#include "julia_assert.h"
#define DEBUG_TYPE "julia_multiversioning"
#undef DEBUG
using namespace llvm;
extern Optional<bool> always_have_fma(Function&);
void replaceUsesWithLoad(Function &F, function_ref<GlobalVariable *(Instruction &I)> should_replace, MDNode *tbaa_const);
namespace {
constexpr uint32_t clone_mask =
JL_TARGET_CLONE_LOOP | JL_TARGET_CLONE_SIMD | JL_TARGET_CLONE_MATH | JL_TARGET_CLONE_CPU | JL_TARGET_CLONE_FLOAT16;
// Treat identical mapping as missing and return `def` in that case.
// We mainly need this to identify cloned function using value map after LLVM cloning
// functions fills the map with identity entries.
template<typename T>
Value *map_get(T &&vmap, Value *key, Value *def=nullptr)
{
auto val = vmap.lookup(key);
if (!val || key == val)
return def;
return val;
}
// Iterate through uses of a particular type.
// Recursively scan through `ConstantExpr` and `ConstantAggregate` use.
template<typename U>
struct ConstantUses {
template<typename T>
struct Info {
Use *use;
T *val;
// If `samebits == true`, the offset the original value appears in the constant.
size_t offset;
// This specify whether the original value appears in the current value in exactly
// the same bit pattern (with possibly an offset determined by `offset`).
bool samebits;
Info(Use *use, T *val, size_t offset, bool samebits) :
use(use),
val(val),
offset(offset),
samebits(samebits)
{
}
Info(Use *use, size_t offset, bool samebits) :
use(use),
val(cast<T>(use->getUser())),
offset(offset),
samebits(samebits)
{
}
};
using UseInfo = Info<U>;
struct Frame : Info<Constant> {
template<typename... Args>
Frame(Args &&... args) :
Info<Constant>(std::forward<Args>(args)...),
cur(this->val->use_empty() ? nullptr : &*this->val->use_begin()),
_next(cur ? cur->getNext() : nullptr)
{
}
private:
void next()
{
cur = _next;
if (!cur)
return;
_next = cur->getNext();
}
Use *cur;
Use *_next;
friend struct ConstantUses;
};
ConstantUses(Constant *c, Module &M)
: stack{Frame(nullptr, c, 0u, true)},
M(M)
{
forward();
}
UseInfo get_info() const
{
auto &top = stack.back();
return UseInfo(top.cur, top.offset, top.samebits);
}
const SmallVector<Frame, 4> &get_stack() const
{
return stack;
}
void next()
{
stack.back().next();
forward();
}
bool done()
{
return stack.empty();
}
private:
void forward();
SmallVector<Frame, 4> stack;
Module &M;
};
template<typename U>
void ConstantUses<U>::forward()
{
assert(!stack.empty());
auto frame = &stack.back();
const DataLayout &DL = M.getDataLayout();
auto pop = [&] {
stack.pop_back();
if (stack.empty()) {
return false;
}
frame = &stack.back();
return true;
};
auto push = [&] (Use *use, Constant *c, size_t offset, bool samebits) {
stack.emplace_back(use, c, offset, samebits);
frame = &stack.back();
};
auto handle_constaggr = [&] (Use *use, ConstantAggregate *aggr) {
if (!frame->samebits) {
push(use, aggr, 0, false);
return;
}
if (auto strct = dyn_cast<ConstantStruct>(aggr)) {
auto layout = DL.getStructLayout(strct->getType());
push(use, strct, frame->offset + layout->getElementOffset(use->getOperandNo()), true);
}
else if (auto ary = dyn_cast<ConstantArray>(aggr)) {
auto elty = ary->getType()->getElementType();
push(use, ary, frame->offset + DL.getTypeAllocSize(elty) * use->getOperandNo(), true);
}
else if (auto vec = dyn_cast<ConstantVector>(aggr)) {
auto elty = vec->getType()->getElementType();
push(use, vec, frame->offset + DL.getTypeAllocSize(elty) * use->getOperandNo(), true);
}
else {
jl_safe_printf("Unknown ConstantAggregate:\n");
llvm_dump(aggr);
abort();
}
};
auto handle_constexpr = [&] (Use *use, ConstantExpr *expr) {
if (!frame->samebits) {
push(use, expr, 0, false);
return;
}
auto opcode = expr->getOpcode();
if (opcode == Instruction::PtrToInt || opcode == Instruction::IntToPtr ||
opcode == Instruction::AddrSpaceCast || opcode == Instruction::BitCast) {
push(use, expr, frame->offset, true);
}
else {
push(use, expr, 0, false);
}
};
while (true) {
auto use = frame->cur;
if (!use) {
if (!pop())
return;
continue;
}
auto user = use->getUser();
if (isa<U>(user))
return;
frame->next();
if (auto aggr = dyn_cast<ConstantAggregate>(user)) {
handle_constaggr(use, aggr);
}
else if (auto expr = dyn_cast<ConstantExpr>(user)) {
handle_constexpr(use, expr);
}
}
}
struct CloneCtx {
struct Target {
int idx;
uint32_t flags;
std::unique_ptr<ValueToValueMapTy> vmap; // ValueToValueMapTy is not movable....
Target(int idx, const jl_target_spec_t &spec) :
idx(idx),
flags(spec.flags),
vmap(new ValueToValueMapTy)
{
}
};
struct Group : Target {
std::vector<Target> clones;
std::set<uint32_t> clone_fs;
Group(int base, const jl_target_spec_t &spec) :
Target(base, spec),
clones{},
clone_fs{}
{}
Function *base_func(Function *orig_f) const
{
if (idx == 0)
return orig_f;
return cast<Function>(vmap->lookup(orig_f));
}
};
CloneCtx(Module &M, function_ref<LoopInfo&(Function&)> GetLI, function_ref<CallGraph&()> GetCG, bool allow_bad_fvars);
void clone_bases();
void collect_func_infos();
void clone_all_partials();
void fix_gv_uses();
void fix_inst_uses();
void emit_metadata();
private:
void prepare_vmap(ValueToValueMapTy &vmap);
bool is_vector(FunctionType *ty) const;
void clone_function(Function *F, Function *new_f, ValueToValueMapTy &vmap);
uint32_t collect_func_info(Function &F);
void check_partial(Group &grp, Target &tgt);
void clone_partial(Group &grp, Target &tgt);
void add_features(Function *F, StringRef name, StringRef features, uint32_t flags) const;
template<typename T>
T *add_comdat(T *G) const;
uint32_t get_func_id(Function *F);
template<typename Stack>
Constant *rewrite_gv_init(const Stack& stack);
std::pair<uint32_t,GlobalVariable*> get_reloc_slot(Function *F);
Constant *get_ptrdiff32(Constant *ptr, Constant *base) const;
template<typename T>
Constant *emit_offset_table(const std::vector<T*> &vars, StringRef name) const;
void rewrite_alias(GlobalAlias *alias, Function* F);
MDNode *tbaa_const;
std::vector<jl_target_spec_t> specs;
std::vector<Group> groups{};
std::vector<Function*> fvars;
std::vector<Constant*> gvars;
Module &M;
function_ref<LoopInfo&(Function&)> GetLI;
function_ref<CallGraph&()> GetCG;
// Map from original function to one based index in `fvars`
std::map<const Function*,uint32_t> func_ids{};
std::vector<Function*> orig_funcs{};
std::vector<uint32_t> func_infos{};
std::set<Function*> cloned{};
// GV addresses and their corresponding function id (i.e. 0-based index in `fvars`)
std::vector<std::pair<Constant*,uint32_t>> gv_relocs{};
// Mapping from function id (i.e. 0-based index in `fvars`) to GVs to be initialized.
std::map<uint32_t,GlobalVariable*> const_relocs;
bool has_veccall{false};
bool allow_bad_fvars{false};
};
template<typename T>
static inline std::vector<T*> consume_gv(Module &M, const char *name, bool allow_bad_fvars)
{
// Get information about sysimg export functions from the two global variables.
// Strip them from the Module so that it's easier to handle the uses.
GlobalVariable *gv = M.getGlobalVariable(name);
assert(gv && gv->hasInitializer());
ArrayType *Ty = cast<ArrayType>(gv->getInitializer()->getType());
unsigned nele = Ty->getArrayNumElements();
std::vector<T*> res(nele);
ConstantArray *ary = nullptr;
if (gv->getInitializer()->isNullValue()) {
for (unsigned i = 0; i < nele; ++i)
res[i] = cast<T>(Constant::getNullValue(Ty->getArrayElementType()));
}
else {
ary = cast<ConstantArray>(gv->getInitializer());
unsigned i = 0;
while (i < nele) {
llvm::Value *val = ary->getOperand(i)->stripPointerCasts();
if (allow_bad_fvars && (!isa<T>(val) || (isa<Function>(val) && cast<Function>(val)->isDeclaration()))) {
// Shouldn't happen in regular use, but can happen in bugpoint.
nele--;
continue;
}
res[i++] = cast<T>(val);
}
res.resize(nele);
}
assert(gv->use_empty());
gv->eraseFromParent();
if (ary && ary->use_empty())
ary->destroyConstant();
return res;
}
// Collect basic information about targets and functions.
CloneCtx::CloneCtx(Module &M, function_ref<LoopInfo&(Function&)> GetLI, function_ref<CallGraph&()> GetCG, bool allow_bad_fvars)
: tbaa_const(tbaa_make_child_with_context(M.getContext(), "jtbaa_const", nullptr, true).first),
specs(jl_get_llvm_clone_targets()),
fvars(consume_gv<Function>(M, "jl_sysimg_fvars", allow_bad_fvars)),
gvars(consume_gv<Constant>(M, "jl_sysimg_gvars", false)),
M(M),
GetLI(GetLI),
GetCG(GetCG),
allow_bad_fvars(allow_bad_fvars)
{
groups.emplace_back(0, specs[0]);
uint32_t ntargets = specs.size();
for (uint32_t i = 1; i < ntargets; i++) {
auto &spec = specs[i];
if (spec.flags & JL_TARGET_CLONE_ALL) {
groups.emplace_back(i, spec);
}
else {
auto base = spec.base;
bool found = false;
for (auto &grp: groups) {
if (grp.idx == base) {
found = true;
grp.clones.emplace_back(i, spec);
break;
}
}
(void)found;
}
}
uint32_t nfvars = fvars.size();
for (uint32_t i = 0; i < nfvars; i++)
func_ids[fvars[i]] = i + 1;
for (auto &F: M) {
if (F.empty())
continue;
orig_funcs.push_back(&F);
}
}
void CloneCtx::prepare_vmap(ValueToValueMapTy &vmap)
{
// Workaround LLVM `CloneFunctionInfo` bug (?) pre-5.0
// The `DICompileUnit`s are being cloned but are not added to the `llvm.dbg.cu` metadata
// which triggers assertions when generating native code/in the verifier.
// Fix this by forcing an identical mapping for all `DICompileUnit` recorded.
// The `DISubprogram` cloning on LLVM 5.0 handles this
// but it doesn't hurt to enforce the identity either.
auto &MD = vmap.MD();
for (auto cu: M.debug_compile_units()) {
MD[cu].reset(cu);
}
}
void CloneCtx::clone_function(Function *F, Function *new_f, ValueToValueMapTy &vmap)
{
Function::arg_iterator DestI = new_f->arg_begin();
for (Function::const_arg_iterator J = F->arg_begin(); J != F->arg_end(); ++J) {
DestI->setName(J->getName());
vmap[&*J] = &*DestI++;
}
SmallVector<ReturnInst*,8> Returns;
#if JL_LLVM_VERSION >= 130000
// We are cloning into the same module
CloneFunctionInto(new_f, F, vmap, CloneFunctionChangeType::GlobalChanges, Returns);
#else
CloneFunctionInto(new_f, F, vmap, true, Returns);
#endif
}
// Clone all clone_all targets. Makes sure that the base targets are all available.
void CloneCtx::clone_bases()
{
if (groups.size() == 1)
return;
uint32_t ngrps = groups.size();
for (uint32_t gid = 1; gid < ngrps; gid++) {
auto &grp = groups[gid];
auto suffix = ".clone_" + std::to_string(grp.idx);
auto &vmap = *grp.vmap;
// Fill in old->new mapping. We need to do this before cloning the function so that
// the intra target calls are automatically fixed up on cloning.
for (auto F: orig_funcs) {
Function *new_f = Function::Create(F->getFunctionType(), F->getLinkage(),
F->getName() + suffix, &M);
new_f->copyAttributesFrom(F);
vmap[F] = new_f;
}
prepare_vmap(vmap);
for (auto F: orig_funcs) {
clone_function(F, cast<Function>(vmap.lookup(F)), vmap);
}
}
}
bool CloneCtx::is_vector(FunctionType *ty) const
{
if (ty->getReturnType()->isVectorTy())
return true;
for (auto arg: ty->params()) {
if (arg->isVectorTy()) {
return true;
}
}
return false;
}
uint32_t CloneCtx::collect_func_info(Function &F)
{
uint32_t flag = 0;
if (!GetLI(F).empty())
flag |= JL_TARGET_CLONE_LOOP;
if (is_vector(F.getFunctionType())) {
flag |= JL_TARGET_CLONE_SIMD;
has_veccall = true;
}
for (auto &bb: F) {
for (auto &I: bb) {
if (auto call = dyn_cast<CallInst>(&I)) {
if (is_vector(call->getFunctionType())) {
has_veccall = true;
flag |= JL_TARGET_CLONE_SIMD;
}
if (auto callee = call->getCalledFunction()) {
auto name = callee->getName();
if (name.startswith("llvm.muladd.") || name.startswith("llvm.fma.")) {
flag |= JL_TARGET_CLONE_MATH;
}
else if (name.startswith("julia.cpu.")) {
if (name.startswith("julia.cpu.have_fma.")) {
// for some platforms we know they always do (or don't) support
// FMA. in those cases we don't need to clone the function.
if (!always_have_fma(*callee).hasValue())
flag |= JL_TARGET_CLONE_CPU;
} else {
flag |= JL_TARGET_CLONE_CPU;
}
}
}
}
else if (auto store = dyn_cast<StoreInst>(&I)) {
if (store->getValueOperand()->getType()->isVectorTy()) {
flag |= JL_TARGET_CLONE_SIMD;
}
}
else if (I.getType()->isVectorTy()) {
flag |= JL_TARGET_CLONE_SIMD;
}
if (auto mathOp = dyn_cast<FPMathOperator>(&I)) {
if (mathOp->getFastMathFlags().any()) {
flag |= JL_TARGET_CLONE_MATH;
}
}
for (size_t i = 0; i < I.getNumOperands(); i++) {
if(I.getOperand(i)->getType()->isHalfTy()){
flag |= JL_TARGET_CLONE_FLOAT16;
}
// Check for BFloat16 when they are added to julia can be done here
}
if (has_veccall && (flag & JL_TARGET_CLONE_SIMD) && (flag & JL_TARGET_CLONE_MATH) &&
(flag & JL_TARGET_CLONE_CPU) && (flag & JL_TARGET_CLONE_FLOAT16)) {
return flag;
}
}
}
return flag;
}
void CloneCtx::collect_func_infos()
{
uint32_t nfuncs = orig_funcs.size();
func_infos.resize(nfuncs);
for (uint32_t i = 0; i < nfuncs; i++) {
func_infos[i] = collect_func_info(*orig_funcs[i]);
}
}
void CloneCtx::clone_all_partials()
{
// First decide what to clone
// Do this before actually cloning the functions
// so that the call graph is easier to understand
for (auto &grp: groups) {
for (auto &tgt: grp.clones) {
check_partial(grp, tgt);
}
}
for (auto &grp: groups) {
for (auto &tgt: grp.clones)
clone_partial(grp, tgt);
// Also set feature strings for base target functions
// now that all the actual cloning is done.
auto &base_spec = specs[grp.idx];
for (auto orig_f: orig_funcs) {
add_features(grp.base_func(orig_f), base_spec.cpu_name,
base_spec.cpu_features, base_spec.flags);
}
}
func_infos.clear(); // We don't need this anymore
}
void CloneCtx::check_partial(Group &grp, Target &tgt)
{
auto flag = specs[tgt.idx].flags & clone_mask;
auto suffix = ".clone_" + std::to_string(tgt.idx);
auto &vmap = *tgt.vmap;
uint32_t nfuncs = func_infos.size();
std::set<Function*> all_origs;
// Use a simple heuristic to decide which function we need to clone.
for (uint32_t i = 0; i < nfuncs; i++) {
if (!(func_infos[i] & flag))
continue;
auto orig_f = orig_funcs[i];
// Fill in old->new mapping. We need to do this before cloning the function so that
// the intra target calls are automatically fixed up on cloning.
auto F = grp.base_func(orig_f);
Function *new_f = Function::Create(F->getFunctionType(), F->getLinkage(),
F->getName() + suffix, &M);
new_f->copyAttributesFrom(F);
vmap[F] = new_f;
if (groups.size() == 1)
cloned.insert(orig_f);
grp.clone_fs.insert(i);
all_origs.insert(orig_f);
}
std::set<Function*> sets[2]{all_origs, std::set<Function*>{}};
auto *cur_set = &sets[0];
auto *next_set = &sets[1];
// Reduce dispatch by expand the cloning set to functions that are directly called by
// and calling cloned functions.
auto &graph = GetCG();
while (!cur_set->empty()) {
for (auto orig_f: *cur_set) {
// Use the uncloned function since it's already in the call graph
auto node = graph[orig_f];
for (const auto &I: *node) {
auto child_node = I.second;
auto orig_child_f = child_node->getFunction();
if (!orig_child_f)
continue;
// Already cloned
if (all_origs.count(orig_child_f))
continue;
bool calling_clone = false;
for (const auto &I2: *child_node) {
auto orig_child_f2 = I2.second->getFunction();
if (!orig_child_f2)
continue;
if (all_origs.count(orig_child_f2)) {
calling_clone = true;
break;
}
}
if (!calling_clone)
continue;
next_set->insert(orig_child_f);
all_origs.insert(orig_child_f);
auto child_f = grp.base_func(orig_child_f);
Function *new_f = Function::Create(child_f->getFunctionType(),
child_f->getLinkage(),
child_f->getName() + suffix, &M);
new_f->copyAttributesFrom(child_f);
vmap[child_f] = new_f;
}
}
std::swap(cur_set, next_set);
next_set->clear();
}
for (uint32_t i = 0; i < nfuncs; i++) {
// Only need to handle expanded functions
if (func_infos[i] & flag)
continue;
auto orig_f = orig_funcs[i];
if (all_origs.count(orig_f)) {
if (groups.size() == 1)
cloned.insert(orig_f);
grp.clone_fs.insert(i);
}
}
}
void CloneCtx::clone_partial(Group &grp, Target &tgt)
{
auto &spec = specs[tgt.idx];
auto &vmap = *tgt.vmap;
uint32_t nfuncs = orig_funcs.size();
prepare_vmap(vmap);
for (uint32_t i = 0; i < nfuncs; i++) {
auto orig_f = orig_funcs[i];
auto F = grp.base_func(orig_f);
if (auto new_v = map_get(vmap, F)) {
auto new_f = cast<Function>(new_v);
assert(new_f != F);
clone_function(F, new_f, vmap);
// We can set the feature strings now since no one is going to
// clone these functions again.
add_features(new_f, spec.cpu_name, spec.cpu_features, spec.flags);
}
}
}
void CloneCtx::add_features(Function *F, StringRef name, StringRef features, uint32_t flags) const
{
auto attr = F->getFnAttribute("target-features");
if (attr.isStringAttribute()) {
std::string new_features(attr.getValueAsString());
new_features += ",";
new_features += features;
F->addFnAttr("target-features", new_features);
}
else {
F->addFnAttr("target-features", features);
}
F->addFnAttr("target-cpu", name);
if (!F->hasFnAttribute(Attribute::OptimizeNone)) {
if (flags & JL_TARGET_OPTSIZE) {
F->addFnAttr(Attribute::OptimizeForSize);
}
else if (flags & JL_TARGET_MINSIZE) {
F->addFnAttr(Attribute::MinSize);
}
}
}
uint32_t CloneCtx::get_func_id(Function *F)
{
auto &ref = func_ids[F];
if (!ref) {
if (allow_bad_fvars && F->isDeclaration()) {
// This should never happen in regular use, but can happen if
// bugpoint deletes the function. Just do something here to
// allow bugpoint to proceed.
return (uint32_t)-1;
}
fvars.push_back(F);
ref = fvars.size();
}
return ref - 1;
}
template<typename Stack>
Constant *CloneCtx::rewrite_gv_init(const Stack& stack)
{
// Null initialize so that LLVM put it in the correct section.
SmallVector<Constant*, 8> args;
Constant *res = ConstantPointerNull::get(cast<PointerType>(stack[0].val->getType()));
uint32_t nlevel = stack.size();
for (uint32_t i = 1; i < nlevel; i++) {
auto &frame = stack[i];
auto val = frame.val;
Use *use = frame.use;
unsigned idx = use->getOperandNo();
unsigned nargs = val->getNumOperands();
args.resize(nargs);
for (unsigned j = 0; j < nargs; j++) {
if (idx == j) {
args[j] = res;
}
else {
args[j] = cast<Constant>(val->getOperand(j));
}
}
if (auto expr = dyn_cast<ConstantExpr>(val)) {
res = expr->getWithOperands(args);
}
else if (auto ary = dyn_cast<ConstantArray>(val)) {
res = ConstantArray::get(ary->getType(), args);
}
else if (auto strct = dyn_cast<ConstantStruct>(val)) {
res = ConstantStruct::get(strct->getType(), args);
}
else if (isa<ConstantVector>(val)) {
res = ConstantVector::get(args);
}
else {
jl_safe_printf("Unknown const use.");
llvm_dump(val);
abort();
}
}
return res;
}
// replace an alias to a function with a trampoline and (uninitialized) global variable slot
void CloneCtx::rewrite_alias(GlobalAlias *alias, Function *F)
{
assert(!is_vector(F->getFunctionType()));
Function *trampoline =
Function::Create(F->getFunctionType(), alias->getLinkage(), "", &M);
trampoline->copyAttributesFrom(F);
trampoline->takeName(alias);
alias->eraseFromParent();
uint32_t id;
GlobalVariable *slot;
std::tie(id, slot) = get_reloc_slot(F);
auto BB = BasicBlock::Create(F->getContext(), "top", trampoline);
IRBuilder<> irbuilder(BB);
auto ptr = irbuilder.CreateLoad(F->getType(), slot);
ptr->setMetadata(llvm::LLVMContext::MD_tbaa, tbaa_const);
ptr->setMetadata(llvm::LLVMContext::MD_invariant_load, MDNode::get(F->getContext(), None));
std::vector<Value *> Args;
for (auto &arg : trampoline->args())
Args.push_back(&arg);
auto call = irbuilder.CreateCall(F->getFunctionType(), ptr, makeArrayRef(Args));
if (F->isVarArg())
#if (defined(_CPU_ARM_) || defined(_CPU_PPC_) || defined(_CPU_PPC64_))
abort(); // musttail support is very bad on ARM, PPC, PPC64 (as of LLVM 3.9)
#else
call->setTailCallKind(CallInst::TCK_MustTail);
#endif
else
call->setTailCallKind(CallInst::TCK_Tail);
if (F->getReturnType() == Type::getVoidTy(F->getContext()))
irbuilder.CreateRetVoid();
else
irbuilder.CreateRet(call);
}
void CloneCtx::fix_gv_uses()
{
auto single_pass = [&] (Function *orig_f) {
bool changed = false;
for (auto uses = ConstantUses<GlobalValue>(orig_f, M); !uses.done(); uses.next()) {
changed = true;
auto &stack = uses.get_stack();
auto info = uses.get_info();
// We only support absolute pointer relocation.
assert(info.samebits);
GlobalVariable *val;
if (auto alias = dyn_cast<GlobalAlias>(info.val)) {
rewrite_alias(alias, orig_f);
continue;
}
else {
val = cast<GlobalVariable>(info.val);
}
assert(info.use->getOperandNo() == 0);
assert(!val->isConstant());
auto fid = get_func_id(orig_f);
auto addr = ConstantExpr::getPtrToInt(val, getSizeTy(val->getContext()));
if (info.offset)
addr = ConstantExpr::getAdd(addr, ConstantInt::get(getSizeTy(val->getContext()), info.offset));
gv_relocs.emplace_back(addr, fid);
val->setInitializer(rewrite_gv_init(stack));
}
return changed;
};
for (auto orig_f: orig_funcs) {
if (groups.size() == 1 && !cloned.count(orig_f))
continue;
while (single_pass(orig_f)) {
}
}
}
std::pair<uint32_t,GlobalVariable*> CloneCtx::get_reloc_slot(Function *F)
{
// Null initialize so that LLVM put it in the correct section.
auto id = get_func_id(F);
auto &slot = const_relocs[id];
if (!slot)
slot = new GlobalVariable(M, F->getType(), false, GlobalVariable::InternalLinkage,
ConstantPointerNull::get(F->getType()),
F->getName() + ".reloc_slot");
return std::make_pair(id, slot);
}
template<typename Stack>
static Value *rewrite_inst_use(const Stack& stack, Value *replace, Instruction *insert_before)
{
SmallVector<Constant*, 8> args;
uint32_t nlevel = stack.size();
for (uint32_t i = 1; i < nlevel; i++) {
auto &frame = stack[i];
auto val = frame.val;
Use *use = frame.use;
unsigned idx = use->getOperandNo();
if (auto expr = dyn_cast<ConstantExpr>(val)) {
auto inst = expr->getAsInstruction();
inst->replaceUsesOfWith(val->getOperand(idx), replace);
inst->insertBefore(insert_before);
replace = inst;
continue;
}
unsigned nargs = val->getNumOperands();
args.resize(nargs);
for (unsigned j = 0; j < nargs; j++) {
auto op = val->getOperand(j);
if (idx == j) {
args[j] = UndefValue::get(op->getType());
}
else {
args[j] = cast<Constant>(op);
}
}
if (auto ary = dyn_cast<ConstantArray>(val)) {
replace = InsertValueInst::Create(ConstantArray::get(ary->getType(), args),
replace, {idx}, "", insert_before);
}
else if (auto strct = dyn_cast<ConstantStruct>(val)) {
replace = InsertValueInst::Create(ConstantStruct::get(strct->getType(), args),
replace, {idx}, "", insert_before);
}
else if (isa<ConstantVector>(val)) {
replace = InsertElementInst::Create(ConstantVector::get(args), replace,
ConstantInt::get(getSizeTy(insert_before->getContext()), idx), "",
insert_before);
}
else {
jl_safe_printf("Unknown const use.");
llvm_dump(val);
abort();
}
}
return replace;
}
void CloneCtx::fix_inst_uses()
{
uint32_t nfuncs = orig_funcs.size();
for (auto &grp: groups) {
auto suffix = ".clone_" + std::to_string(grp.idx);
for (uint32_t i = 0; i < nfuncs; i++) {
if (!grp.clone_fs.count(i))
continue;
auto orig_f = orig_funcs[i];
auto F = grp.base_func(orig_f);
replaceUsesWithLoad(*F, [&](Instruction &I) -> GlobalVariable * {
uint32_t id;
GlobalVariable *slot;
auto use_f = I.getFunction();
if (!use_f->getName().endswith(suffix))
return nullptr;
std::tie(id, slot) = get_reloc_slot(orig_f);
return slot;
}, tbaa_const);
}
}
}
template<typename T>
inline T *CloneCtx::add_comdat(T *G) const
{
#if defined(_OS_WINDOWS_)
// 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;
}
Constant *CloneCtx::get_ptrdiff32(Constant *ptr, Constant *base) const
{
if (ptr->getType()->isPointerTy())
ptr = ConstantExpr::getPtrToInt(ptr, getSizeTy(ptr->getContext()));
auto ptrdiff = ConstantExpr::getSub(ptr, base);
return sizeof(void*) == 8 ? ConstantExpr::getTrunc(ptrdiff, Type::getInt32Ty(ptr->getContext())) : ptrdiff;
}
template<typename T>
Constant *CloneCtx::emit_offset_table(const std::vector<T*> &vars, StringRef name) const
{
auto T_int32 = Type::getInt32Ty(M.getContext());
auto T_size = getSizeTy(M.getContext());
uint32_t nvars = vars.size();
Constant *base = nullptr;
if (nvars > 0) {
base = ConstantExpr::getBitCast(vars[0], T_size->getPointerTo());
add_comdat(GlobalAlias::create(T_size, 0, GlobalVariable::ExternalLinkage,
name + "_base",
base, &M));
} else {
base = ConstantExpr::getNullValue(T_size->getPointerTo());
}
auto vbase = ConstantExpr::getPtrToInt(base, T_size);
std::vector<Constant*> offsets(nvars + 1);
offsets[0] = ConstantInt::get(T_int32, nvars);
if (nvars > 0) {
offsets[1] = ConstantInt::get(T_int32, 0);
for (uint32_t i = 1; i < nvars; i++)
offsets[i + 1] = get_ptrdiff32(vars[i], vbase);
}
ArrayType *vars_type = ArrayType::get(T_int32, nvars + 1);
add_comdat(new GlobalVariable(M, vars_type, true,
GlobalVariable::ExternalLinkage,
ConstantArray::get(vars_type, offsets),
name + "_offsets"));
return vbase;
}
void CloneCtx::emit_metadata()
{
uint32_t nfvars = fvars.size();
if (allow_bad_fvars && nfvars == 0) {
// Will result in a non-loadable sysimg, but `allow_bad_fvars` is for bugpoint only
return;
}
// Store back the information about exported functions.
auto fbase = emit_offset_table(fvars, "jl_sysimg_fvars");
auto gbase = emit_offset_table(gvars, "jl_sysimg_gvars");
uint32_t ntargets = specs.size();
SmallVector<Target*, 8> targets(ntargets);
for (auto &grp: groups) {
targets[grp.idx] = &grp;
for (auto &tgt: grp.clones) {
targets[tgt.idx] = &tgt;
}
}
if (has_veccall) {
M.addModuleFlag(Module::Max, "julia.mv.veccall", 1);
}
// Generate `jl_dispatch_reloc_slots`
std::set<uint32_t> shared_relocs;
{
auto T_int32 = Type::getInt32Ty(M.getContext());
std::stable_sort(gv_relocs.begin(), gv_relocs.end(),
[] (const std::pair<Constant*,uint32_t> &lhs,
const std::pair<Constant*,uint32_t> &rhs) {
return lhs.second < rhs.second;
});
std::vector<Constant*> values{nullptr};
uint32_t gv_reloc_idx = 0;
uint32_t ngv_relocs = gv_relocs.size();
for (uint32_t id = 0; id < nfvars; id++) {
// TODO:
// explicitly set section? so that we are sure the relocation slots
// are in the same section as `gbase`.
auto id_v = ConstantInt::get(T_int32, id);
for (; gv_reloc_idx < ngv_relocs && gv_relocs[gv_reloc_idx].second == id;
gv_reloc_idx++) {
shared_relocs.insert(id);
values.push_back(id_v);
values.push_back(get_ptrdiff32(gv_relocs[gv_reloc_idx].first, gbase));
}
auto it = const_relocs.find(id);
if (it != const_relocs.end()) {
shared_relocs.insert(id);
values.push_back(id_v);
values.push_back(get_ptrdiff32(it->second, gbase));
}
}
values[0] = ConstantInt::get(T_int32, values.size() / 2);
ArrayType *vars_type = ArrayType::get(T_int32, values.size());
add_comdat(new GlobalVariable(M, vars_type, true, GlobalVariable::ExternalLinkage,
ConstantArray::get(vars_type, values),
"jl_dispatch_reloc_slots"));
}
// Generate `jl_dispatch_fvars_idxs` and `jl_dispatch_fvars_offsets`
{
std::vector<uint32_t> idxs;
std::vector<Constant*> offsets;
for (uint32_t i = 0; i < ntargets; i++) {
auto tgt = targets[i];
auto &spec = specs[i];