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codegen: ensure i1 bool is widened to i8 before storing
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Teach value_to_pointer to convert primitive types to their stored
representation first, to avoid exposing undef bits later (via memcpy).

Take this opportunity to also generalizes the support for zext Bool to
anywhere inside any struct for changing any bitwidth to a multiple of 8
bytes. This would change a vector like <2 x i4> from occupying i8 to i16
(c.f. LLVM's LangRef), if such an operation were expressible in Julia
today. And take this opportunity to do a bit of code cleanup, now that
codegen is better and using helpers from LLVM.

Fixes #52127
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@vtjnash
vtjnash committed Nov 16, 2023
1 parent 2fb06a7 commit 29b85e8
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Showing 4 changed files with 98 additions and 60 deletions.
3 changes: 0 additions & 3 deletions src/cgutils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -783,9 +783,6 @@ static Type *_julia_struct_to_llvm(jl_codegen_params_t *ctx, LLVMContext &ctxt,
lty = JuliaType::get_prjlvalue_ty(ctxt);
isvector = false;
}
else if (ty == (jl_value_t*)jl_bool_type) {
lty = getInt8Ty(ctxt);
}
else if (jl_is_uniontype(ty)) {
// pick an Integer type size such that alignment will generally be correct,
// and always end with an Int8 (selector byte).
Expand Down
27 changes: 8 additions & 19 deletions src/codegen.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2163,9 +2163,12 @@ static bool valid_as_globalinit(const Value *v) {
return isa<Constant>(v);
}

static Value *zext_struct(jl_codectx_t &ctx, Value *V);

static inline jl_cgval_t value_to_pointer(jl_codectx_t &ctx, Value *v, jl_value_t *typ, Value *tindex)
{
Value *loc;
v = zext_struct(ctx, v);
if (valid_as_globalinit(v)) { // llvm can't handle all the things that could be inside a ConstantExpr
assert(jl_is_concrete_type(typ)); // not legal to have an unboxed abstract type
loc = get_pointer_to_constant(ctx.emission_context, cast<Constant>(v), Align(julia_alignment(typ)), "_j_const", *jl_Module);
Expand Down Expand Up @@ -2291,17 +2294,6 @@ static void alloc_def_flag(jl_codectx_t &ctx, jl_varinfo_t& vi)

// --- utilities ---

static Constant *undef_value_for_type(Type *T) {
auto tracked = CountTrackedPointers(T);
Constant *undef;
if (tracked.count)
// make sure gc pointers (including ptr_phi of union-split) are initialized to NULL
undef = Constant::getNullValue(T);
else
undef = UndefValue::get(T);
return undef;
}

static void CreateTrap(IRBuilder<> &irbuilder, bool create_new_block)
{
Function *f = irbuilder.GetInsertBlock()->getParent();
Expand Down Expand Up @@ -3574,7 +3566,7 @@ static bool emit_builtin_call(jl_codectx_t &ctx, jl_cgval_t *ret, jl_value_t *f,
if (f == jl_builtin_is && nargs == 2) {
// emit comparison test
Value *ans = emit_f_is(ctx, argv[1], argv[2]);
*ret = mark_julia_type(ctx, ctx.builder.CreateZExt(ans, getInt8Ty(ctx.builder.getContext())), false, jl_bool_type);
*ret = mark_julia_type(ctx, ans, false, jl_bool_type);
return true;
}

Expand Down Expand Up @@ -3613,8 +3605,6 @@ static bool emit_builtin_call(jl_codectx_t &ctx, jl_cgval_t *ret, jl_value_t *f,
if (jl_is_type_type(ty.typ) && !jl_has_free_typevars(ty.typ)) {
jl_value_t *tp0 = jl_tparam0(ty.typ);
Value *isa_result = emit_isa(ctx, arg, tp0, Twine()).first;
if (isa_result->getType() == getInt1Ty(ctx.builder.getContext()))
isa_result = ctx.builder.CreateZExt(isa_result, getInt8Ty(ctx.builder.getContext()));
*ret = mark_julia_type(ctx, isa_result, false, jl_bool_type);
return true;
}
Expand Down Expand Up @@ -5551,16 +5541,15 @@ static Value *emit_condition(jl_codectx_t &ctx, const jl_cgval_t &condV, const T
emit_typecheck(ctx, condV, (jl_value_t*)jl_bool_type, msg);
}
if (isbool) {
Value *cond = emit_unbox(ctx, getInt8Ty(ctx.builder.getContext()), condV, (jl_value_t*)jl_bool_type);
assert(cond->getType() == getInt8Ty(ctx.builder.getContext()));
return ctx.builder.CreateXor(ctx.builder.CreateTrunc(cond, getInt1Ty(ctx.builder.getContext())), ConstantInt::get(getInt1Ty(ctx.builder.getContext()), 1));
Value *cond = emit_unbox(ctx, getInt1Ty(ctx.builder.getContext()), condV, (jl_value_t*)jl_bool_type);
return ctx.builder.CreateNot(cond);
}
if (condV.isboxed) {
return ctx.builder.CreateICmpEQ(boxed(ctx, condV),
track_pjlvalue(ctx, literal_pointer_val(ctx, jl_false)));
}
// not a boolean
return ConstantInt::get(getInt1Ty(ctx.builder.getContext()), 0); // TODO: replace with Undef
// not a boolean (unreachable dead code)
return UndefValue::get(getInt1Ty(ctx.builder.getContext()));
}

static Value *emit_condition(jl_codectx_t &ctx, jl_value_t *cond, const Twine &msg)
Expand Down
119 changes: 81 additions & 38 deletions src/intrinsics.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -173,12 +173,7 @@ static Type *INTT(Type *t, const DataLayout &DL)

static Value *uint_cnvt(jl_codectx_t &ctx, Type *to, Value *x)
{
Type *t = x->getType();
if (t == to)
return x;
if (to->getPrimitiveSizeInBits() < x->getType()->getPrimitiveSizeInBits())
return ctx.builder.CreateTrunc(x, to);
return ctx.builder.CreateZExt(x, to);
return ctx.builder.CreateZExtOrTrunc(x, to);
}

static Constant *julia_const_to_llvm(jl_codectx_t &ctx, const void *ptr, jl_datatype_t *bt)
Expand Down Expand Up @@ -317,25 +312,90 @@ static Constant *julia_const_to_llvm(jl_codectx_t &ctx, jl_value_t *e)
return julia_const_to_llvm(ctx, e, (jl_datatype_t*)bt);
}

static Constant *undef_value_for_type(Type *T) {
auto tracked = CountTrackedPointers(T);
Constant *undef;
if (tracked.count)
// make sure gc pointers (including ptr_phi of union-split) are initialized to NULL
undef = Constant::getNullValue(T);
else
undef = UndefValue::get(T);
return undef;
}

// rebuild a struct type with any i1 Bool (e.g. the llvmcall type) widened to i8 (the native size for memcpy)
static Type *zext_struct_type(Type *T)
{
if (auto *AT = dyn_cast<ArrayType>(T)) {
return ArrayType::get(AT->getElementType(), AT->getNumElements());
}
else if (auto *ST = dyn_cast<StructType>(T)) {
SmallVector<Type*> Elements(ST->element_begin(), ST->element_end());
for (size_t i = 0; i < Elements.size(); i++) {
Elements[i] = zext_struct_type(Elements[i]);
}
return StructType::get(ST->getContext(), Elements, ST->isPacked());
}
else if (auto *VT = dyn_cast<VectorType>(T)) {
return VectorType::get(zext_struct_type(VT->getElementType()), VT);
}
else if (auto *IT = dyn_cast<IntegerType>(T)) {
unsigned BitWidth = IT->getBitWidth();
if (alignTo(BitWidth, 8) != BitWidth)
return IntegerType::get(IT->getContext(), alignTo(BitWidth, 8));
}
return T;
}

// rebuild a struct with any i1 Bool (e.g. the llvmcall type) widened to i8 (the native size for memcpy)
static Value *zext_struct_helper(jl_codectx_t &ctx, Value *V, Type *T2)
{
Type *T = V->getType();
if (T == T2)
return V;
if (auto *AT = dyn_cast<ArrayType>(T2)) {
Value *V2 = undef_value_for_type(AT);
for (size_t i = 0; i < AT->getNumElements(); i++) {
Value *E = zext_struct_helper(ctx, ctx.builder.CreateExtractValue(V, i), AT->getElementType());
V2 = ctx.builder.CreateInsertValue(V2, E, i);
}
return V2;
}
else if (auto *ST = dyn_cast<StructType>(T2)) {
Value *V2 = undef_value_for_type(ST);
for (size_t i = 0; i < ST->getNumElements(); i++) {
Value *E = zext_struct_helper(ctx, ctx.builder.CreateExtractValue(V, i), ST->getElementType(i));
V2 = ctx.builder.CreateInsertValue(V2, E, i);
}
return V2;
}
else if (T2->isIntegerTy() || T2->isVectorTy()) {
return ctx.builder.CreateZExt(V, T2);
}
return V;
}

static Value *zext_struct(jl_codectx_t &ctx, Value *V)
{
return zext_struct_helper(ctx, V, zext_struct_type(V->getType()));
}

static Value *emit_unboxed_coercion(jl_codectx_t &ctx, Type *to, Value *unboxed)
{
if (unboxed->getType() == to)
return unboxed;
if (CastInst::castIsValid(Instruction::Trunc, unboxed, to))
return ctx.builder.CreateTrunc(unboxed, to);
unboxed = zext_struct(ctx, unboxed);
Type *ty = unboxed->getType();
if (ty == to)
return unboxed;
bool frompointer = ty->isPointerTy();
bool topointer = to->isPointerTy();
const DataLayout &DL = jl_Module->getDataLayout();
if (ty->isIntegerTy(1) && to->isIntegerTy(8)) {
// bools may be stored internally as int8
unboxed = ctx.builder.CreateZExt(unboxed, to);
}
else if (ty->isIntegerTy(8) && to->isIntegerTy(1)) {
// bools may be stored internally as int8
unboxed = ctx.builder.CreateTrunc(unboxed, to);
}
else if (ty->isVoidTy() || DL.getTypeSizeInBits(ty) != DL.getTypeSizeInBits(to)) {
if (ty->isVoidTy() || DL.getTypeSizeInBits(ty) != DL.getTypeSizeInBits(to)) {
// this can happen in dead code
//emit_unreachable(ctx);
CreateTrap(ctx.builder);
return UndefValue::get(to);
}
if (frompointer && topointer) {
Expand Down Expand Up @@ -380,7 +440,7 @@ static Value *emit_unbox(jl_codectx_t &ctx, Type *to, const jl_cgval_t &x, jl_va
if (type_is_ghost(to)) {
return NULL;
}
//emit_unreachable(ctx);
CreateTrap(ctx.builder);
return UndefValue::get(to); // type mismatch error
}

Expand Down Expand Up @@ -446,17 +506,9 @@ static void emit_unbox_store(jl_codectx_t &ctx, const jl_cgval_t &x, Value *dest
return;
}

Value *unboxed = nullptr;
if (!x.ispointer()) { // already unboxed, but sometimes need conversion
unboxed = x.V;
assert(unboxed);
}

// bools stored as int8, but can be narrowed to int1 often
if (x.typ == (jl_value_t*)jl_bool_type)
unboxed = emit_unbox(ctx, getInt8Ty(ctx.builder.getContext()), x, (jl_value_t*)jl_bool_type);

if (unboxed) {
if (!x.ispointer()) { // already unboxed, but sometimes need conversion (e.g. f32 -> i32)
assert(x.V);
Value *unboxed = zext_struct(ctx, x.V);
Type *dest_ty = unboxed->getType()->getPointerTo();
if (dest->getType() != dest_ty)
dest = emit_bitcast(ctx, dest, dest_ty);
Expand Down Expand Up @@ -1445,23 +1497,14 @@ static Value *emit_untyped_intrinsic(jl_codectx_t &ctx, intrinsic f, Value **arg
Intrinsic::smul_with_overflow :
Intrinsic::umul_with_overflow)))));
FunctionCallee intr = Intrinsic::getDeclaration(jl_Module, intr_id, ArrayRef<Type*>(t));
Value *res = ctx.builder.CreateCall(intr, {x, y});
Value *val = ctx.builder.CreateExtractValue(res, ArrayRef<unsigned>(0));
setName(ctx.emission_context, val, "checked");
Value *obit = ctx.builder.CreateExtractValue(res, ArrayRef<unsigned>(1));
setName(ctx.emission_context, obit, "overflow");
Value *obyte = ctx.builder.CreateZExt(obit, getInt8Ty(ctx.builder.getContext()));
Value *tupval = ctx.builder.CreateCall(intr, {x, y});

jl_value_t *params[2];
params[0] = xtyp;
params[1] = (jl_value_t*)jl_bool_type;
jl_datatype_t *tuptyp = (jl_datatype_t*)jl_apply_tuple_type_v(params, 2);
*newtyp = tuptyp;

Value *tupval;
tupval = UndefValue::get(julia_type_to_llvm(ctx, (jl_value_t*)tuptyp));
tupval = ctx.builder.CreateInsertValue(tupval, val, ArrayRef<unsigned>(0));
tupval = ctx.builder.CreateInsertValue(tupval, obyte, ArrayRef<unsigned>(1));
return tupval;
}

Expand Down
9 changes: 9 additions & 0 deletions test/llvmcall2.jl
View file
Original file line number Diff line number Diff line change
Expand Up @@ -73,3 +73,12 @@ end
jl_str = unsafe_string(str)
@test length(jl_str) > 4
end


# boolean structs
const NT4I = NTuple{4, VecElement{Int}}
const NT4B = NTuple{4, VecElement{Bool}}
f_nt4b(x, y) = ccall("llvm.sadd.with.overflow", llvmcall, Pair{NT4B, NT4B}, (NT4B, NT4B), x, y)
f_nt4i(x, y) = ccall("llvm.sadd.with.overflow", llvmcall, Pair{NT4I, NT4B}, (NT4I, NT4I), x, y)
@test f_nt4b((false, true, false, true), (false, false, true, true)) === (NT4B((false, true, true, false)) => NT4B((false, false, false, true)))
@test f_nt4i((typemin(Int), 0, typemax(Int), typemax(Int)), (-1, typemax(Int),-1, 1)) === (NT4I((typemax(Int), typemax(Int), typemax(Int)-1, typemin(Int))) => NT4B((true, false, false, true)))

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