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builder_methods.rs
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// HACK(eddyb) avoids rewriting all of the imports (see `lib.rs` and `build.rs`).
use crate::maybe_pqp_cg_ssa as rustc_codegen_ssa;
use super::Builder;
use crate::abi::ConvSpirvType;
use crate::builder_spirv::{BuilderCursor, SpirvConst, SpirvValue, SpirvValueExt, SpirvValueKind};
use crate::codegen_cx::CodegenCx;
use crate::custom_insts::{CustomInst, CustomOp};
use crate::spirv_type::SpirvType;
use itertools::Itertools;
use rspirv::dr::{InsertPoint, Instruction, Operand};
use rspirv::spirv::{Capability, MemoryModel, MemorySemantics, Op, Scope, StorageClass, Word};
use rustc_apfloat::{Float, Round, Status, ieee};
use rustc_codegen_ssa::MemFlags;
use rustc_codegen_ssa::common::{
AtomicOrdering, AtomicRmwBinOp, IntPredicate, RealPredicate, SynchronizationScope, TypeKind,
};
use rustc_codegen_ssa::mir::operand::{OperandRef, OperandValue};
use rustc_codegen_ssa::mir::place::PlaceRef;
use rustc_codegen_ssa::traits::{
BackendTypes, BaseTypeCodegenMethods, BuilderMethods, ConstCodegenMethods,
LayoutTypeCodegenMethods, OverflowOp,
};
use rustc_data_structures::fx::FxHashSet;
use rustc_middle::bug;
use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
use rustc_middle::ty::layout::LayoutOf;
use rustc_middle::ty::{self, Ty};
use rustc_span::Span;
use rustc_target::abi::call::FnAbi;
use rustc_target::abi::{Align, BackendRepr, Scalar, Size, WrappingRange};
use smallvec::SmallVec;
use std::borrow::Cow;
use std::cell::Cell;
use std::iter::{self, empty};
use std::ops::RangeInclusive;
macro_rules! simple_op {
(
$func_name:ident, $inst_name:ident
$(, fold_const {
$(int($fold_int_lhs:ident, $fold_int_rhs:ident) => $fold_int:expr)?
})?
) => {
fn $func_name(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value {
assert_ty_eq!(self, lhs.ty, rhs.ty);
let result_type = lhs.ty;
$(if let Some(const_lhs) = self.builder.lookup_const(lhs) {
if let Some(const_rhs) = self.builder.lookup_const(rhs) {
match self.lookup_type(result_type) {
$(SpirvType::Integer(bits, signed) => {
let size = Size::from_bits(bits);
let as_u128 = |const_val| {
let x = match const_val {
SpirvConst::Scalar(x) => x,
_ => return None,
};
Some(if signed {
size.sign_extend(x) as u128
} else {
size.truncate(x)
})
};
if let Some($fold_int_lhs) = as_u128(const_lhs) {
if let Some($fold_int_rhs) = as_u128(const_rhs) {
return self.const_uint_big(result_type, $fold_int);
}
}
})?
_ => {}
}
}
})?
self.emit()
.$inst_name(result_type, None, lhs.def(self), rhs.def(self))
.unwrap()
.with_type(result_type)
}
};
}
// shl and shr allow different types as their operands
macro_rules! simple_op_unchecked_type {
($func_name:ident, $inst_name:ident) => {
fn $func_name(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value {
self.emit()
.$inst_name(lhs.ty, None, lhs.def(self), rhs.def(self))
.unwrap()
.with_type(lhs.ty)
}
};
}
macro_rules! simple_uni_op {
($func_name:ident, $inst_name:ident) => {
fn $func_name(&mut self, val: Self::Value) -> Self::Value {
self.emit()
.$inst_name(val.ty, None, val.def(self))
.unwrap()
.with_type(val.ty)
}
};
}
fn memset_fill_u16(b: u8) -> u16 {
b as u16 | ((b as u16) << 8)
}
fn memset_fill_u32(b: u8) -> u32 {
b as u32 | ((b as u32) << 8) | ((b as u32) << 16) | ((b as u32) << 24)
}
fn memset_fill_u64(b: u8) -> u64 {
b as u64
| ((b as u64) << 8)
| ((b as u64) << 16)
| ((b as u64) << 24)
| ((b as u64) << 32)
| ((b as u64) << 40)
| ((b as u64) << 48)
| ((b as u64) << 56)
}
fn memset_dynamic_scalar(
builder: &Builder<'_, '_>,
fill_var: Word,
byte_width: usize,
is_float: bool,
) -> Word {
let composite_type = SpirvType::Vector {
element: SpirvType::Integer(8, false).def(builder.span(), builder),
count: byte_width as u32,
}
.def(builder.span(), builder);
let composite = builder
.emit()
.composite_construct(
composite_type,
None,
iter::repeat(fill_var).take(byte_width),
)
.unwrap();
let result_type = if is_float {
SpirvType::Float(byte_width as u32 * 8)
} else {
SpirvType::Integer(byte_width as u32 * 8, false)
};
builder
.emit()
.bitcast(result_type.def(builder.span(), builder), None, composite)
.unwrap()
}
impl<'a, 'tcx> Builder<'a, 'tcx> {
fn ordering_to_semantics_def(&self, ordering: AtomicOrdering) -> SpirvValue {
let mut invalid_seq_cst = false;
let semantics = match ordering {
AtomicOrdering::Unordered | AtomicOrdering::Relaxed => MemorySemantics::NONE,
// Note: rustc currently has AtomicOrdering::Consume commented out, if it ever becomes
// uncommented, it should be MakeVisible | Acquire.
AtomicOrdering::Acquire => MemorySemantics::MAKE_VISIBLE | MemorySemantics::ACQUIRE,
AtomicOrdering::Release => MemorySemantics::MAKE_AVAILABLE | MemorySemantics::RELEASE,
AtomicOrdering::AcquireRelease => {
MemorySemantics::MAKE_AVAILABLE
| MemorySemantics::MAKE_VISIBLE
| MemorySemantics::ACQUIRE_RELEASE
}
AtomicOrdering::SequentiallyConsistent => {
let emit = self.emit();
let memory_model = emit.module_ref().memory_model.as_ref().unwrap();
if memory_model.operands[1].unwrap_memory_model() == MemoryModel::Vulkan {
invalid_seq_cst = true;
}
MemorySemantics::MAKE_AVAILABLE
| MemorySemantics::MAKE_VISIBLE
| MemorySemantics::SEQUENTIALLY_CONSISTENT
}
};
let semantics = self.constant_u32(self.span(), semantics.bits());
if invalid_seq_cst {
self.zombie(
semantics.def(self),
"cannot use AtomicOrdering=SequentiallyConsistent on Vulkan memory model \
(check if AcquireRelease fits your needs)",
);
}
semantics
}
fn memset_const_pattern(&self, ty: &SpirvType<'tcx>, fill_byte: u8) -> Word {
match *ty {
SpirvType::Void => self.fatal("memset invalid on void pattern"),
SpirvType::Bool => self.fatal("memset invalid on bool pattern"),
SpirvType::Integer(width, _signedness) => match width {
8 => self.constant_u8(self.span(), fill_byte).def(self),
16 => self
.constant_u16(self.span(), memset_fill_u16(fill_byte))
.def(self),
32 => self
.constant_u32(self.span(), memset_fill_u32(fill_byte))
.def(self),
64 => self
.constant_u64(self.span(), memset_fill_u64(fill_byte))
.def(self),
_ => self.fatal(format!(
"memset on integer width {width} not implemented yet"
)),
},
SpirvType::Float(width) => match width {
32 => self
.constant_f32(self.span(), f32::from_bits(memset_fill_u32(fill_byte)))
.def(self),
64 => self
.constant_f64(self.span(), f64::from_bits(memset_fill_u64(fill_byte)))
.def(self),
_ => self.fatal(format!("memset on float width {width} not implemented yet")),
},
SpirvType::Adt { .. } => self.fatal("memset on structs not implemented yet"),
SpirvType::Vector { element, count } | SpirvType::Matrix { element, count } => {
let elem_pat = self.memset_const_pattern(&self.lookup_type(element), fill_byte);
self.constant_composite(
ty.def(self.span(), self),
iter::repeat(elem_pat).take(count as usize),
)
.def(self)
}
SpirvType::Array { element, count } => {
let elem_pat = self.memset_const_pattern(&self.lookup_type(element), fill_byte);
let count = self.builder.lookup_const_scalar(count).unwrap() as usize;
self.constant_composite(
ty.def(self.span(), self),
iter::repeat(elem_pat).take(count),
)
.def(self)
}
SpirvType::RuntimeArray { .. } => {
self.fatal("memset on runtime arrays not implemented yet")
}
SpirvType::Pointer { .. } => self.fatal("memset on pointers not implemented yet"),
SpirvType::Function { .. } => self.fatal("memset on functions not implemented yet"),
SpirvType::Image { .. } => self.fatal("cannot memset image"),
SpirvType::Sampler => self.fatal("cannot memset sampler"),
SpirvType::SampledImage { .. } => self.fatal("cannot memset sampled image"),
SpirvType::InterfaceBlock { .. } => self.fatal("cannot memset interface block"),
SpirvType::AccelerationStructureKhr => {
self.fatal("cannot memset acceleration structure")
}
SpirvType::RayQueryKhr => self.fatal("cannot memset ray query"),
}
}
fn memset_dynamic_pattern(&self, ty: &SpirvType<'tcx>, fill_var: Word) -> Word {
match *ty {
SpirvType::Void => self.fatal("memset invalid on void pattern"),
SpirvType::Bool => self.fatal("memset invalid on bool pattern"),
SpirvType::Integer(width, _signedness) => match width {
8 => fill_var,
16 => memset_dynamic_scalar(self, fill_var, 2, false),
32 => memset_dynamic_scalar(self, fill_var, 4, false),
64 => memset_dynamic_scalar(self, fill_var, 8, false),
_ => self.fatal(format!(
"memset on integer width {width} not implemented yet"
)),
},
SpirvType::Float(width) => match width {
32 => memset_dynamic_scalar(self, fill_var, 4, true),
64 => memset_dynamic_scalar(self, fill_var, 8, true),
_ => self.fatal(format!("memset on float width {width} not implemented yet")),
},
SpirvType::Adt { .. } => self.fatal("memset on structs not implemented yet"),
SpirvType::Array { element, count } => {
let elem_pat = self.memset_dynamic_pattern(&self.lookup_type(element), fill_var);
let count = self.builder.lookup_const_scalar(count).unwrap() as usize;
self.emit()
.composite_construct(
ty.def(self.span(), self),
None,
iter::repeat(elem_pat).take(count),
)
.unwrap()
}
SpirvType::Vector { element, count } | SpirvType::Matrix { element, count } => {
let elem_pat = self.memset_dynamic_pattern(&self.lookup_type(element), fill_var);
self.emit()
.composite_construct(
ty.def(self.span(), self),
None,
iter::repeat(elem_pat).take(count as usize),
)
.unwrap()
}
SpirvType::RuntimeArray { .. } => {
self.fatal("memset on runtime arrays not implemented yet")
}
SpirvType::Pointer { .. } => self.fatal("memset on pointers not implemented yet"),
SpirvType::Function { .. } => self.fatal("memset on functions not implemented yet"),
SpirvType::Image { .. } => self.fatal("cannot memset image"),
SpirvType::Sampler => self.fatal("cannot memset sampler"),
SpirvType::SampledImage { .. } => self.fatal("cannot memset sampled image"),
SpirvType::InterfaceBlock { .. } => self.fatal("cannot memset interface block"),
SpirvType::AccelerationStructureKhr => {
self.fatal("cannot memset acceleration structure")
}
SpirvType::RayQueryKhr => self.fatal("cannot memset ray query"),
}
}
fn memset_constant_size(&mut self, ptr: SpirvValue, pat: SpirvValue, size_bytes: u64) {
let size_elem = self
.lookup_type(pat.ty)
.sizeof(self)
.expect("Memset on unsized values not supported");
let count = size_bytes / size_elem.bytes();
if count == 1 {
self.store(pat, ptr, Align::from_bytes(0).unwrap());
} else {
for index in 0..count {
let const_index = self.constant_u32(self.span(), index as u32);
let gep_ptr = self.gep(pat.ty, ptr, &[const_index]);
self.store(pat, gep_ptr, Align::from_bytes(0).unwrap());
}
}
}
// TODO: Test this is correct
fn memset_dynamic_size(&mut self, ptr: SpirvValue, pat: SpirvValue, size_bytes: SpirvValue) {
let size_elem = self
.lookup_type(pat.ty)
.sizeof(self)
.expect("Unable to memset a dynamic sized object");
let size_elem_const = self.constant_int(size_bytes.ty, size_elem.bytes().into());
let zero = self.constant_int(size_bytes.ty, 0);
let one = self.constant_int(size_bytes.ty, 1);
let zero_align = Align::from_bytes(0).unwrap();
let header_bb = self.append_sibling_block("memset_header");
let body_bb = self.append_sibling_block("memset_body");
let exit_bb = self.append_sibling_block("memset_exit");
let count = self.udiv(size_bytes, size_elem_const);
let index = self.alloca(self.lookup_type(count.ty).sizeof(self).unwrap(), zero_align);
self.store(zero, index, zero_align);
self.br(header_bb);
self.switch_to_block(header_bb);
let current_index = self.load(count.ty, index, zero_align);
let cond = self.icmp(IntPredicate::IntULT, current_index, count);
self.cond_br(cond, body_bb, exit_bb);
self.switch_to_block(body_bb);
let gep_ptr = self.gep(pat.ty, ptr, &[current_index]);
self.store(pat, gep_ptr, zero_align);
let current_index_plus_1 = self.add(current_index, one);
self.store(current_index_plus_1, index, zero_align);
self.br(header_bb);
self.switch_to_block(exit_bb);
}
fn zombie_convert_ptr_to_u(&self, def: Word) {
if !self
.builder
.has_capability(Capability::PhysicalStorageBufferAddresses)
{
self.zombie(def, "cannot convert pointers to integers without OpCapability PhysicalStorageBufferAddresses");
}
}
fn zombie_convert_u_to_ptr(&self, def: Word) {
if !self
.builder
.has_capability(Capability::PhysicalStorageBufferAddresses)
{
self.zombie(def, "cannot convert integers to pointers without OpCapability PhysicalStorageBufferAddresses");
}
}
fn zombie_ptr_equal(&self, def: Word, inst: &str) {
if !self.builder.has_capability(Capability::VariablePointers) {
self.zombie(
def,
&format!("{inst} without OpCapability VariablePointers"),
);
}
}
/// Convenience wrapper for `adjust_pointer_for_sized_access`, falling back
/// on choosing `ty` as the leaf's type (and casting `ptr` to a pointer to it).
//
// HACK(eddyb) temporary workaround for untyped pointers upstream.
// FIXME(eddyb) replace with untyped memory SPIR-V + `qptr` or similar.
fn adjust_pointer_for_typed_access(
&mut self,
ptr: SpirvValue,
ty: <Self as BackendTypes>::Type,
) -> (SpirvValue, <Self as BackendTypes>::Type) {
self.lookup_type(ty)
.sizeof(self)
.and_then(|size| self.adjust_pointer_for_sized_access(ptr, size))
.unwrap_or_else(|| (self.pointercast(ptr, self.type_ptr_to(ty)), ty))
}
/// If `ptr`'s pointee type contains any prefix field/element of size `size`,
/// i.e. some leaf which can be used for all accesses of size `size`, return
/// `ptr` adjusted to point to the innermost such leaf, and the leaf's type.
//
// FIXME(eddyb) technically this duplicates `pointercast`, but the main use
// of `pointercast` is being replaced by this, and this can be more efficient.
//
// HACK(eddyb) temporary workaround for untyped pointers upstream.
// FIXME(eddyb) replace with untyped memory SPIR-V + `qptr` or similar.
fn adjust_pointer_for_sized_access(
&mut self,
ptr: SpirvValue,
size: Size,
) -> Option<(SpirvValue, <Self as BackendTypes>::Type)> {
let ptr = ptr.strip_ptrcasts();
let pointee_ty = match self.lookup_type(ptr.ty) {
SpirvType::Pointer { pointee, .. } => pointee,
other => self.fatal(format!("non-pointer type: {other:?}")),
};
// FIXME(eddyb) this isn't efficient, `recover_access_chain_from_offset`
// could instead be doing all the extra digging itself.
let mut indices = SmallVec::<[_; 8]>::new();
let mut leaf_ty = pointee_ty;
while let Some((inner_indices, inner_ty)) = self.recover_access_chain_from_offset(
leaf_ty,
Size::ZERO,
Some(size)..=Some(size),
None,
) {
indices.extend(inner_indices);
leaf_ty = inner_ty;
}
let leaf_ptr_ty = (self.lookup_type(leaf_ty).sizeof(self) == Some(size))
.then(|| self.type_ptr_to(leaf_ty))?;
let leaf_ptr = if indices.is_empty() {
// Compare pointee types instead of pointer types as storage class might be different.
assert_ty_eq!(self, pointee_ty, leaf_ty);
ptr
} else {
let indices = indices
.into_iter()
.map(|idx| self.constant_u32(self.span(), idx).def(self))
.collect::<Vec<_>>();
self.emit()
.in_bounds_access_chain(leaf_ptr_ty, None, ptr.def(self), indices)
.unwrap()
.with_type(leaf_ptr_ty)
};
Some((leaf_ptr, leaf_ty))
}
/// If possible, return the appropriate `OpAccessChain` indices for going
/// from a pointer to `ty`, to a pointer to some leaf field/element having
/// a size that fits `leaf_size_range` (and, optionally, the type `leaf_ty`),
/// while adding `offset` bytes.
///
/// That is, try to turn `((_: *T) as *u8).add(offset) as *Leaf` into a series
/// of struct field and array/vector element accesses.
fn recover_access_chain_from_offset(
&self,
mut ty: <Self as BackendTypes>::Type,
mut offset: Size,
// FIXME(eddyb) using `None` for "unsized" is a pretty bad design.
leaf_size_or_unsized_range: RangeInclusive<Option<Size>>,
leaf_ty: Option<<Self as BackendTypes>::Type>,
) -> Option<(SmallVec<[u32; 8]>, <Self as BackendTypes>::Type)> {
assert_ne!(Some(ty), leaf_ty);
// HACK(eddyb) this has the correct ordering (`Sized(_) < Unsized`).
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
enum MaybeSized {
Sized(Size),
Unsized,
}
let leaf_size_range = {
let r = leaf_size_or_unsized_range;
let [start, end] =
[r.start(), r.end()].map(|x| x.map_or(MaybeSized::Unsized, MaybeSized::Sized));
start..=end
};
// NOTE(eddyb) `ty` and `ty_kind`/`ty_size` should be kept in sync.
let mut ty_kind = self.lookup_type(ty);
let mut indices = SmallVec::new();
loop {
let ty_size;
match ty_kind {
SpirvType::Adt {
field_types,
field_offsets,
..
} => {
let (i, field_ty, field_ty_kind, field_ty_size, offset_in_field) = field_offsets
.iter()
.enumerate()
.find_map(|(i, &field_offset)| {
if field_offset > offset {
return None;
}
// Grab the actual field type to be able to confirm that
// the leaf is somewhere inside the field.
let field_ty = field_types[i];
let field_ty_kind = self.lookup_type(field_ty);
let field_ty_size = field_ty_kind
.sizeof(self).map_or(MaybeSized::Unsized, MaybeSized::Sized);
let offset_in_field = offset - field_offset;
if MaybeSized::Sized(offset_in_field) < field_ty_size
// If the field is a zero sized type, check the
// expected size and type to get the correct entry
|| offset_in_field == Size::ZERO
&& leaf_size_range.contains(&MaybeSized::Sized(Size::ZERO)) && leaf_ty == Some(field_ty)
{
Some((i, field_ty, field_ty_kind, field_ty_size, offset_in_field))
} else {
None
}
})?;
ty = field_ty;
ty_kind = field_ty_kind;
ty_size = field_ty_size;
indices.push(i as u32);
offset = offset_in_field;
}
SpirvType::Vector { element, .. }
| SpirvType::Array { element, .. }
| SpirvType::RuntimeArray { element }
| SpirvType::Matrix { element, .. } => {
ty = element;
ty_kind = self.lookup_type(ty);
let stride = ty_kind.sizeof(self)?;
ty_size = MaybeSized::Sized(stride);
indices.push((offset.bytes() / stride.bytes()).try_into().ok()?);
offset = Size::from_bytes(offset.bytes() % stride.bytes());
}
_ => return None,
}
// Avoid digging beyond the point the leaf could actually fit.
if ty_size < *leaf_size_range.start() {
return None;
}
if offset == Size::ZERO
&& leaf_size_range.contains(&ty_size)
&& leaf_ty.map_or(true, |leaf_ty| leaf_ty == ty)
{
return Some((indices, ty));
}
}
}
fn maybe_inbounds_gep(
&mut self,
ty: Word,
ptr: SpirvValue,
combined_indices: &[SpirvValue],
is_inbounds: bool,
) -> SpirvValue {
let (&ptr_base_index, indices) = combined_indices.split_first().unwrap();
// The first index is an offset to the pointer, the rest are actual members.
// https://llvm.org/docs/GetElementPtr.html
// "An OpAccessChain instruction is the equivalent of an LLVM getelementptr instruction where the first index element is zero."
// https://github.com/gpuweb/gpuweb/issues/33
let mut result_pointee_type = ty;
let indices: Vec<_> = indices
.iter()
.map(|index| {
result_pointee_type = match self.lookup_type(result_pointee_type) {
SpirvType::Array { element, .. } | SpirvType::RuntimeArray { element } => {
element
}
_ => self.fatal(format!(
"GEP not implemented for type {}",
self.debug_type(result_pointee_type)
)),
};
index.def(self)
})
.collect();
// Special-case field accesses through a `pointercast`, to access the
// right field in the original type, for the `Logical` addressing model.
let ptr = ptr.strip_ptrcasts();
let ptr_id = ptr.def(self);
let original_pointee_ty = match self.lookup_type(ptr.ty) {
SpirvType::Pointer { pointee, .. } => pointee,
other => self.fatal(format!("gep called on non-pointer type: {other:?}")),
};
// HACK(eddyb) `struct_gep` itself is falling out of use, as it's being
// replaced upstream by `ptr_add` (aka `inbounds_gep` with byte offsets).
//
// FIXME(eddyb) get rid of everything other than:
// - constant byte offset (`ptr_add`?)
// - dynamic indexing of a single array
let const_ptr_offset = self
.builder
.lookup_const_scalar(ptr_base_index)
.and_then(|idx| Some(u64::try_from(idx).ok()? * self.lookup_type(ty).sizeof(self)?));
if let Some(const_ptr_offset) = const_ptr_offset {
if let Some((base_indices, base_pointee_ty)) = self.recover_access_chain_from_offset(
original_pointee_ty,
const_ptr_offset,
Some(Size::ZERO)..=None,
None,
) {
// FIXME(eddyb) this condition is pretty limiting, but
// eventually it shouldn't matter if GEPs are going away.
if ty == base_pointee_ty || indices.is_empty() {
let result_pointee_type = if indices.is_empty() {
base_pointee_ty
} else {
result_pointee_type
};
let indices = base_indices
.into_iter()
.map(|idx| self.constant_u32(self.span(), idx).def(self))
.chain(indices)
.collect();
return self.emit_access_chain(
self.type_ptr_to(result_pointee_type),
ptr_id,
None,
indices,
is_inbounds,
);
}
}
}
let result_type = self.type_ptr_to(result_pointee_type);
// Check if `ptr_id` is defined by an `OpAccessChain`, and if it is,
// grab its base pointer and indices.
//
// FIXME(eddyb) this could get ridiculously expensive, at the very least
// it could use `.rev()`, hoping the base pointer was recently defined?
let maybe_original_access_chain = if ty == original_pointee_ty {
let emit = self.emit();
let module = emit.module_ref();
let func = &module.functions[emit.selected_function().unwrap()];
let base_ptr_and_combined_indices = func
.all_inst_iter()
.find(|inst| inst.result_id == Some(ptr_id))
.and_then(|ptr_def_inst| {
if matches!(
ptr_def_inst.class.opcode,
Op::AccessChain | Op::InBoundsAccessChain
) {
let base_ptr = ptr_def_inst.operands[0].unwrap_id_ref();
let indices = ptr_def_inst.operands[1..]
.iter()
.map(|op| op.unwrap_id_ref())
.collect::<Vec<_>>();
Some((base_ptr, indices))
} else {
None
}
});
base_ptr_and_combined_indices
} else {
None
};
if let Some((original_ptr, mut original_indices)) = maybe_original_access_chain {
// Transform the following:
// OpAccessChain original_ptr [a, b, c]
// OpPtrAccessChain ptr base [d, e, f]
// into
// OpAccessChain original_ptr [a, b, c + base, d, e, f]
// to remove the need for OpPtrAccessChain
let last = original_indices.last_mut().unwrap();
*last = self
.add(last.with_type(ptr_base_index.ty), ptr_base_index)
.def(self);
original_indices.extend(indices);
return self.emit_access_chain(
result_type,
original_ptr,
None,
original_indices,
is_inbounds,
);
}
// HACK(eddyb) temporary workaround for untyped pointers upstream.
// FIXME(eddyb) replace with untyped memory SPIR-V + `qptr` or similar.
let ptr = self.pointercast(ptr, self.type_ptr_to(ty));
let ptr_id = ptr.def(self);
self.emit_access_chain(
result_type,
ptr_id,
Some(ptr_base_index),
indices,
is_inbounds,
)
}
fn emit_access_chain(
&self,
result_type: <Self as BackendTypes>::Type,
pointer: Word,
ptr_base_index: Option<SpirvValue>,
indices: Vec<Word>,
is_inbounds: bool,
) -> SpirvValue {
let mut emit = self.emit();
let non_zero_ptr_base_index =
ptr_base_index.filter(|&idx| self.builder.lookup_const_scalar(idx) != Some(0));
if let Some(ptr_base_index) = non_zero_ptr_base_index {
let result = if is_inbounds {
emit.in_bounds_ptr_access_chain(
result_type,
None,
pointer,
ptr_base_index.def(self),
indices,
)
} else {
emit.ptr_access_chain(
result_type,
None,
pointer,
ptr_base_index.def(self),
indices,
)
}
.unwrap();
self.zombie(result, "cannot offset a pointer to an arbitrary element");
result
} else {
if is_inbounds {
emit.in_bounds_access_chain(result_type, None, pointer, indices)
} else {
emit.access_chain(result_type, None, pointer, indices)
}
.unwrap()
}
.with_type(result_type)
}
fn fptoint_sat(
&mut self,
signed: bool,
val: SpirvValue,
dest_ty: <Self as BackendTypes>::Type,
) -> SpirvValue {
// This uses the old llvm emulation to implement saturation
let src_ty = self.cx.val_ty(val);
let (float_ty, int_ty) = if self.cx.type_kind(src_ty) == TypeKind::Vector {
assert_eq!(
self.cx.vector_length(src_ty),
self.cx.vector_length(dest_ty)
);
(self.cx.element_type(src_ty), self.cx.element_type(dest_ty))
} else {
(src_ty, dest_ty)
};
let int_width = self.cx().int_width(int_ty);
let float_width = self.cx().float_width(float_ty);
// LLVM's fpto[su]i returns undef when the input x is infinite, NaN, or does not fit into the
// destination integer type after rounding towards zero. This `undef` value can cause UB in
// safe code (see issue #10184), so we implement a saturating conversion on top of it:
// Semantically, the mathematical value of the input is rounded towards zero to the next
// mathematical integer, and then the result is clamped into the range of the destination
// integer type. Positive and negative infinity are mapped to the maximum and minimum value of
// the destination integer type. NaN is mapped to 0.
//
// Define f_min and f_max as the largest and smallest (finite) floats that are exactly equal to
// a value representable in int_ty.
// They are exactly equal to int_ty::{MIN,MAX} if float_ty has enough significand bits.
// Otherwise, int_ty::MAX must be rounded towards zero, as it is one less than a power of two.
// int_ty::MIN, however, is either zero or a negative power of two and is thus exactly
// representable. Note that this only works if float_ty's exponent range is sufficiently large.
// f16 or 256 bit integers would break this property. Right now the smallest float type is f32
// with exponents ranging up to 127, which is barely enough for i128::MIN = -2^127.
// On the other hand, f_max works even if int_ty::MAX is greater than float_ty::MAX. Because
// we're rounding towards zero, we just get float_ty::MAX (which is always an integer).
// This already happens today with u128::MAX = 2^128 - 1 > f32::MAX.
let int_max = |signed: bool, int_width: u64| -> u128 {
let shift_amount = 128 - int_width;
if signed {
i128::MAX as u128 >> shift_amount
} else {
u128::MAX >> shift_amount
}
};
let int_min = |signed: bool, int_width: u64| -> i128 {
if signed {
i128::MIN >> (128 - int_width)
} else {
0
}
};
let compute_clamp_bounds_single = |signed: bool, int_width: u64| -> (u128, u128) {
let rounded_min =
ieee::Single::from_i128_r(int_min(signed, int_width), Round::TowardZero);
assert_eq!(rounded_min.status, Status::OK);
let rounded_max =
ieee::Single::from_u128_r(int_max(signed, int_width), Round::TowardZero);
assert!(rounded_max.value.is_finite());
(rounded_min.value.to_bits(), rounded_max.value.to_bits())
};
let compute_clamp_bounds_double = |signed: bool, int_width: u64| -> (u128, u128) {
let rounded_min =
ieee::Double::from_i128_r(int_min(signed, int_width), Round::TowardZero);
assert_eq!(rounded_min.status, Status::OK);
let rounded_max =
ieee::Double::from_u128_r(int_max(signed, int_width), Round::TowardZero);
assert!(rounded_max.value.is_finite());
(rounded_min.value.to_bits(), rounded_max.value.to_bits())
};
// To implement saturation, we perform the following steps:
//
// 1. Cast x to an integer with fpto[su]i. This may result in undef.
// 2. Compare x to f_min and f_max, and use the comparison results to select:
// a) int_ty::MIN if x < f_min or x is NaN
// b) int_ty::MAX if x > f_max
// c) the result of fpto[su]i otherwise
// 3. If x is NaN, return 0.0, otherwise return the result of step 2.
//
// This avoids resulting undef because values in range [f_min, f_max] by definition fit into the
// destination type. It creates an undef temporary, but *producing* undef is not UB. Our use of
// undef does not introduce any non-determinism either.
// More importantly, the above procedure correctly implements saturating conversion.
// Proof (sketch):
// If x is NaN, 0 is returned by definition.
// Otherwise, x is finite or infinite and thus can be compared with f_min and f_max.
// This yields three cases to consider:
// (1) if x in [f_min, f_max], the result of fpto[su]i is returned, which agrees with
// saturating conversion for inputs in that range.
// (2) if x > f_max, then x is larger than int_ty::MAX. This holds even if f_max is rounded
// (i.e., if f_max < int_ty::MAX) because in those cases, nextUp(f_max) is already larger
// than int_ty::MAX. Because x is larger than int_ty::MAX, the return value of int_ty::MAX
// is correct.
// (3) if x < f_min, then x is smaller than int_ty::MIN. As shown earlier, f_min exactly equals
// int_ty::MIN and therefore the return value of int_ty::MIN is correct.
// QED.
let float_bits_to_llval = |bx: &mut Self, bits| {
let bits_llval = match float_width {
32 => bx.cx().const_u32(bits as u32),
64 => bx.cx().const_u64(bits as u64),
n => bug!("unsupported float width {}", n),
};
bx.bitcast(bits_llval, float_ty)
};
let (f_min, f_max) = match float_width {
32 => compute_clamp_bounds_single(signed, int_width),
64 => compute_clamp_bounds_double(signed, int_width),
n => bug!("unsupported float width {}", n),
};
let f_min = float_bits_to_llval(self, f_min);
let f_max = float_bits_to_llval(self, f_max);
let int_max = self.cx().const_uint_big(int_ty, int_max(signed, int_width));
let int_min = self
.cx()
.const_uint_big(int_ty, int_min(signed, int_width) as u128);
let zero = self.cx().const_uint(int_ty, 0);
// If we're working with vectors, constants must be "splatted": the constant is duplicated
// into each lane of the vector. The algorithm stays the same, we are just using the
// same constant across all lanes.
let maybe_splat = |bx: &mut Self, val| {
if bx.cx().type_kind(dest_ty) == TypeKind::Vector {
bx.vector_splat(bx.vector_length(dest_ty), val)
} else {
val
}
};
let f_min = maybe_splat(self, f_min);
let f_max = maybe_splat(self, f_max);
let int_max = maybe_splat(self, int_max);
let int_min = maybe_splat(self, int_min);
let zero = maybe_splat(self, zero);
// Step 1 ...
let fptosui_result = if signed {
self.fptosi(val, dest_ty)
} else {
self.fptoui(val, dest_ty)
};
let less_or_nan = self.fcmp(RealPredicate::RealULT, val, f_min);
let greater = self.fcmp(RealPredicate::RealOGT, val, f_max);
// Step 2: We use two comparisons and two selects, with %s1 being the
// result:
// %less_or_nan = fcmp ult %x, %f_min
// %greater = fcmp olt %x, %f_max
// %s0 = select %less_or_nan, int_ty::MIN, %fptosi_result
// %s1 = select %greater, int_ty::MAX, %s0
// Note that %less_or_nan uses an *unordered* comparison. This
// comparison is true if the operands are not comparable (i.e., if x is
// NaN). The unordered comparison ensures that s1 becomes int_ty::MIN if
// x is NaN.
//
// Performance note: Unordered comparison can be lowered to a "flipped"
// comparison and a negation, and the negation can be merged into the
// select. Therefore, it not necessarily any more expensive than an
// ordered ("normal") comparison. Whether these optimizations will be
// performed is ultimately up to the backend, but at least x86 does
// perform them.
let s0 = self.select(less_or_nan, int_min, fptosui_result);
let s1 = self.select(greater, int_max, s0);
// Step 3: NaN replacement.
// For unsigned types, the above step already yielded int_ty::MIN == 0 if x is NaN.
// Therefore we only need to execute this step for signed integer types.
if signed {
// LLVM has no isNaN predicate, so we use (x == x) instead
let cmp = self.fcmp(RealPredicate::RealOEQ, val, val);
self.select(cmp, s1, zero)
} else {
s1
}
}
// HACK(eddyb) helper shared by `typed_alloca` and `alloca`.
fn declare_func_local_var(
&mut self,
ty: <Self as BackendTypes>::Type,
_align: Align,
) -> SpirvValue {
let ptr_ty = self.type_ptr_to(ty);
// "All OpVariable instructions in a function must be the first instructions in the first block."
let mut builder = self.emit();
builder.select_block(Some(0)).unwrap();
let index = {
let block = &builder.module_ref().functions[builder.selected_function().unwrap()]
.blocks[builder.selected_block().unwrap()];
block
.instructions
.iter()
.enumerate()
.find_map(|(index, inst)| {
if inst.class.opcode != Op::Variable {
Some(InsertPoint::FromBegin(index))
} else {
None
}
})
.unwrap_or(InsertPoint::End)
};
// TODO: rspirv doesn't have insert_variable function
let result_id = builder.id();
let inst = Instruction::new(Op::Variable, Some(ptr_ty), Some(result_id), vec![
Operand::StorageClass(StorageClass::Function),
]);
builder.insert_into_block(index, inst).unwrap();
result_id.with_type(ptr_ty)
}
}
impl<'a, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'tcx> {
type CodegenCx = CodegenCx<'tcx>;
fn build(cx: &'a Self::CodegenCx, llbb: Self::BasicBlock) -> Self {
let cursor = cx.builder.select_block_by_id(llbb);
// FIXME(eddyb) change `Self::Function` to be more like a function index.
let current_fn = {
let emit = cx.emit_with_cursor(cursor);
let selected_function = emit.selected_function().unwrap();
let selected_function = &emit.module_ref().functions[selected_function];
let def_inst = selected_function.def.as_ref().unwrap();
let def = def_inst.result_id.unwrap();
let ty = def_inst.operands[1].unwrap_id_ref();
def.with_type(ty)
};
Self {
cx,
cursor,
current_fn,
current_span: Default::default(),
}
}
fn cx(&self) -> &Self::CodegenCx {
self.cx
}
fn llbb(&self) -> Self::BasicBlock {