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Rollup merge of #110021 - scottmcm:fix-110005, r=compiler-errors

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Fix a couple ICEs in the new `CastKind::Transmute` code

Check the sizes of the immediates, rather than the overall types, when deciding whether we can convert types without going through memory.

Fixes #110005
Fixes #109992
Fixes #110032
cc `@matthiaskrgr`
This commit is contained in:
Dylan DPC 2023-04-10 14:13:14 +05:30 committed by GitHub
commit b8725520af
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4 changed files with 261 additions and 38 deletions
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25
compiler/rustc_codegen_ssa/src/mir/operand.rs
View File

@ -259,6 +259,31 @@ pub fn extract_field<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
}
impl<'a, 'tcx, V: CodegenObject> OperandValue<V> {
/// Returns an `OperandValue` that's generally UB to use in any way.
///
/// Depending on the `layout`, returns an `Immediate` or `Pair` containing
/// poison value(s), or a `Ref` containing a poison pointer.
///
/// Supports sized types only.
pub fn poison<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
bx: &mut Bx,
layout: TyAndLayout<'tcx>,
) -> OperandValue<V> {
assert!(layout.is_sized());
if bx.cx().is_backend_immediate(layout) {
let ibty = bx.cx().immediate_backend_type(layout);
OperandValue::Immediate(bx.const_poison(ibty))
} else if bx.cx().is_backend_scalar_pair(layout) {
let ibty0 = bx.cx().scalar_pair_element_backend_type(layout, 0, true);
let ibty1 = bx.cx().scalar_pair_element_backend_type(layout, 1, true);
OperandValue::Pair(bx.const_poison(ibty0), bx.const_poison(ibty1))
} else {
let bty = bx.cx().backend_type(layout);
let ptr_bty = bx.cx().type_ptr_to(bty);
OperandValue::Ref(bx.const_poison(ptr_bty), None, layout.align.abi)
}
}
pub fn store<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
self,
bx: &mut Bx,

107
compiler/rustc_codegen_ssa/src/mir/rvalue.rs
View File

@ -158,17 +158,6 @@ fn codegen_transmute(
debug_assert!(src.layout.is_sized());
debug_assert!(dst.layout.is_sized());
if src.layout.size != dst.layout.size
|| src.layout.abi.is_uninhabited()
|| dst.layout.abi.is_uninhabited()
{
// In all of these cases it's UB to run this transmute, but that's
// known statically so might as well trap for it, rather than just
// making it unreachable.
bx.abort();
return;
}
if let Some(val) = self.codegen_transmute_operand(bx, src, dst.layout) {
val.store(bx, dst);
return;
@ -202,8 +191,21 @@ fn codegen_transmute_operand(
operand: OperandRef<'tcx, Bx::Value>,
cast: TyAndLayout<'tcx>,
) -> Option<OperandValue<Bx::Value>> {
// Callers already checked that the layout sizes match
debug_assert_eq!(operand.layout.size, cast.size);
// Check for transmutes that are always UB.
if operand.layout.size != cast.size
|| operand.layout.abi.is_uninhabited()
|| cast.abi.is_uninhabited()
{
if !operand.layout.abi.is_uninhabited() {
// Since this is known statically and the input could have existed
// without already having hit UB, might as well trap for it.
bx.abort();
}
// Because this transmute is UB, return something easy to generate,
// since it's fine that later uses of the value are probably UB.
return Some(OperandValue::poison(bx, cast));
}
let operand_kind = self.value_kind(operand.layout);
let cast_kind = self.value_kind(cast);
@ -222,10 +224,20 @@ fn codegen_transmute_operand(
bug!("Found {operand_kind:?} for operand {operand:?}");
};
if let OperandValueKind::Immediate(out_scalar) = cast_kind {
let cast_bty = bx.backend_type(cast);
Some(OperandValue::Immediate(Self::transmute_immediate(
bx, imm, in_scalar, out_scalar, cast_bty,
)))
match (in_scalar, out_scalar) {
(ScalarOrZst::Zst, ScalarOrZst::Zst) => {
Some(OperandRef::new_zst(bx, cast).val)
}
(ScalarOrZst::Scalar(in_scalar), ScalarOrZst::Scalar(out_scalar))
if in_scalar.size(self.cx) == out_scalar.size(self.cx) =>
{
let cast_bty = bx.backend_type(cast);
Some(OperandValue::Immediate(
self.transmute_immediate(bx, imm, in_scalar, out_scalar, cast_bty),
))
}
_ => None,
}
} else {
None
}
@ -234,12 +246,15 @@ fn codegen_transmute_operand(
let OperandValueKind::Pair(in_a, in_b) = operand_kind else {
bug!("Found {operand_kind:?} for operand {operand:?}");
};
if let OperandValueKind::Pair(out_a, out_b) = cast_kind {
if let OperandValueKind::Pair(out_a, out_b) = cast_kind
&& in_a.size(self.cx) == out_a.size(self.cx)
&& in_b.size(self.cx) == out_b.size(self.cx)
{
let out_a_ibty = bx.scalar_pair_element_backend_type(cast, 0, false);
let out_b_ibty = bx.scalar_pair_element_backend_type(cast, 1, false);
Some(OperandValue::Pair(
Self::transmute_immediate(bx, imm_a, in_a, out_a, out_a_ibty),
Self::transmute_immediate(bx, imm_b, in_b, out_b, out_b_ibty),
self.transmute_immediate(bx, imm_a, in_a, out_a, out_a_ibty),
self.transmute_immediate(bx, imm_b, in_b, out_b, out_b_ibty),
))
} else {
None
@ -254,12 +269,15 @@ fn codegen_transmute_operand(
/// `to_backend_ty` must be the *non*-immediate backend type (so it will be
/// `i8`, not `i1`, for `bool`-like types.)
fn transmute_immediate(
&self,
bx: &mut Bx,
mut imm: Bx::Value,
from_scalar: abi::Scalar,
to_scalar: abi::Scalar,
to_backend_ty: Bx::Type,
) -> Bx::Value {
debug_assert_eq!(from_scalar.size(self.cx), to_scalar.size(self.cx));
use abi::Primitive::*;
imm = bx.from_immediate(imm);
imm = match (from_scalar.primitive(), to_scalar.primitive()) {
@ -831,14 +849,6 @@ pub fn rvalue_creates_operand(&self, rvalue: &mir::Rvalue<'tcx>, span: Span) ->
let operand_ty = operand.ty(self.mir, self.cx.tcx());
let cast_layout = self.cx.layout_of(self.monomorphize(cast_ty));
let operand_layout = self.cx.layout_of(self.monomorphize(operand_ty));
if operand_layout.size != cast_layout.size
|| operand_layout.abi.is_uninhabited()
|| cast_layout.abi.is_uninhabited()
{
// Send UB cases to the full form so the operand version can
// `bitcast` without worrying about malformed IR.
return false;
}
match (self.value_kind(operand_layout), self.value_kind(cast_layout)) {
// Can always load from a pointer as needed
@ -847,9 +857,12 @@ pub fn rvalue_creates_operand(&self, rvalue: &mir::Rvalue<'tcx>, span: Span) ->
// Need to generate an `alloc` to get a pointer from an immediate
(OperandValueKind::Immediate(..) | OperandValueKind::Pair(..), OperandValueKind::Ref) => false,
// When we have scalar immediates, we can convert them as needed
(OperandValueKind::Immediate(..), OperandValueKind::Immediate(..)) |
(OperandValueKind::Pair(..), OperandValueKind::Pair(..)) => true,
// When we have scalar immediates, we can only convert things
// where the sizes match, to avoid endianness questions.
(OperandValueKind::Immediate(a), OperandValueKind::Immediate(b)) =>
a.size(self.cx) == b.size(self.cx),
(OperandValueKind::Pair(a0, a1), OperandValueKind::Pair(b0, b1)) =>
a0.size(self.cx) == b0.size(self.cx) && a1.size(self.cx) == b1.size(self.cx),
// Send mixings between scalars and pairs through the memory route
// FIXME: Maybe this could use insertvalue/extractvalue instead?
@ -887,13 +900,18 @@ fn value_kind(&self, layout: TyAndLayout<'tcx>) -> OperandValueKind {
if self.cx.is_backend_immediate(layout) {
debug_assert!(!self.cx.is_backend_scalar_pair(layout));
OperandValueKind::Immediate(match layout.abi {
abi::Abi::Scalar(s) => s,
abi::Abi::Vector { element, .. } => element,
x => bug!("Couldn't translate {x:?} as backend immediate"),
abi::Abi::Scalar(s) => ScalarOrZst::Scalar(s),
abi::Abi::Vector { element, .. } => ScalarOrZst::Scalar(element),
_ if layout.is_zst() => ScalarOrZst::Zst,
x => span_bug!(self.mir.span, "Couldn't translate {x:?} as backend immediate"),
})
} else if self.cx.is_backend_scalar_pair(layout) {
let abi::Abi::ScalarPair(s1, s2) = layout.abi else {
bug!("Couldn't translate {:?} as backend scalar pair", layout.abi)
span_bug!(
self.mir.span,
"Couldn't translate {:?} as backend scalar pair",
layout.abi,
);
};
OperandValueKind::Pair(s1, s2)
} else {
@ -902,9 +920,26 @@ fn value_kind(&self, layout: TyAndLayout<'tcx>) -> OperandValueKind {
}
}
/// The variants of this match [`OperandValue`], giving details about the
/// backend values that will be held in that other type.
#[derive(Debug, Copy, Clone)]
enum OperandValueKind {
Ref,
Immediate(abi::Scalar),
Immediate(ScalarOrZst),
Pair(abi::Scalar, abi::Scalar),
}
#[derive(Debug, Copy, Clone)]
enum ScalarOrZst {
Zst,
Scalar(abi::Scalar),
}
impl ScalarOrZst {
pub fn size(self, cx: &impl abi::HasDataLayout) -> abi::Size {
match self {
ScalarOrZst::Zst => abi::Size::ZERO,
ScalarOrZst::Scalar(s) => s.size(cx),
}
}
}

35
tests/codegen/intrinsics/transmute-x64.rs Normal file
View File

@ -0,0 +1,35 @@
// compile-flags: -O -C no-prepopulate-passes
// only-x86_64 (it's using arch-specific types)
// min-llvm-version: 15.0 # this test assumes `ptr`s
#![crate_type = "lib"]
use std::arch::x86_64::{__m128, __m128i, __m256i};
use std::mem::transmute;
// CHECK-LABEL: @check_sse_float_to_int(
#[no_mangle]
pub unsafe fn check_sse_float_to_int(x: __m128) -> __m128i {
// CHECK-NOT: alloca
// CHECK: %1 = load <4 x float>, ptr %x, align 16
// CHECK: store <4 x float> %1, ptr %0, align 16
transmute(x)
}
// CHECK-LABEL: @check_sse_pair_to_avx(
#[no_mangle]
pub unsafe fn check_sse_pair_to_avx(x: (__m128i, __m128i)) -> __m256i {
// CHECK-NOT: alloca
// CHECK: %1 = load <4 x i64>, ptr %x, align 16
// CHECK: store <4 x i64> %1, ptr %0, align 32
transmute(x)
}
// CHECK-LABEL: @check_sse_pair_from_avx(
#[no_mangle]
pub unsafe fn check_sse_pair_from_avx(x: __m256i) -> (__m128i, __m128i) {
// CHECK-NOT: alloca
// CHECK: %1 = load <4 x i64>, ptr %x, align 32
// CHECK: store <4 x i64> %1, ptr %0, align 16
transmute(x)
}

132
tests/codegen/intrinsics/transmute.rs
View File

@ -8,7 +8,7 @@
#![feature(inline_const)]
#![allow(unreachable_code)]
use std::mem::transmute;
use std::mem::{transmute, MaybeUninit};
// Some of the cases here are statically rejected by `mem::transmute`, so
// we need to generate custom MIR for those cases to get to codegen.
@ -54,6 +54,32 @@ pub unsafe fn check_smaller_size(x: u32) -> u16 {
}
}
// CHECK-LABEL: @check_smaller_array(
#[no_mangle]
#[custom_mir(dialect = "runtime", phase = "initial")]
pub unsafe fn check_smaller_array(x: [u32; 7]) -> [u32; 3] {
// CHECK: call void @llvm.trap
mir!{
{
RET = CastTransmute(x);
Return()
}
}
}
// CHECK-LABEL: @check_bigger_array(
#[no_mangle]
#[custom_mir(dialect = "runtime", phase = "initial")]
pub unsafe fn check_bigger_array(x: [u32; 3]) -> [u32; 7] {
// CHECK: call void @llvm.trap
mir!{
{
RET = CastTransmute(x);
Return()
}
}
}
// CHECK-LABEL: @check_to_uninhabited(
#[no_mangle]
#[custom_mir(dialect = "runtime", phase = "initial")]
@ -71,7 +97,7 @@ pub unsafe fn check_to_uninhabited(x: u16) -> BigNever {
#[no_mangle]
#[custom_mir(dialect = "runtime", phase = "initial")]
pub unsafe fn check_from_uninhabited(x: BigNever) -> u16 {
// CHECK: call void @llvm.trap
// CHECK: ret i16 poison
mir!{
{
RET = CastTransmute(x);
@ -301,3 +327,105 @@ pub unsafe fn check_float_from_pointer(x: *const ()) -> f64 {
// CHECK: store i64 %x.1, ptr %{{.+}}, align 1
transmute(x)
}
// CHECK-LABEL: @check_heterogeneous_integer_pair(
#[no_mangle]
pub unsafe fn check_heterogeneous_integer_pair(x: (i32, bool)) -> (bool, u32) {
// CHECK: store i32 %x.0
// CHECK: %[[WIDER:.+]] = zext i1 %x.1 to i8
// CHECK: store i8 %[[WIDER]]
// CHECK: %[[BYTE:.+]] = load i8
// CHECK: trunc i8 %[[BYTE:.+]] to i1
// CHECK: load i32
transmute(x)
}
// CHECK-LABEL: @check_heterogeneous_float_pair(
#[no_mangle]
pub unsafe fn check_heterogeneous_float_pair(x: (f64, f32)) -> (f32, f64) {
// CHECK: store double %x.0
// CHECK: store float %x.1
// CHECK: %[[A:.+]] = load float
// CHECK: %[[B:.+]] = load double
// CHECK: %[[P:.+]] = insertvalue { float, double } poison, float %[[A]], 0
// CHECK: insertvalue { float, double } %[[P]], double %[[B]], 1
transmute(x)
}
// CHECK-LABEL: @check_issue_110005(
#[no_mangle]
pub unsafe fn check_issue_110005(x: (usize, bool)) -> Option<Box<[u8]>> {
// CHECK: store i64 %x.0
// CHECK: %[[WIDER:.+]] = zext i1 %x.1 to i8
// CHECK: store i8 %[[WIDER]]
// CHECK: load ptr
// CHECK: load i64
transmute(x)
}
// CHECK-LABEL: @check_pair_to_dst_ref(
#[no_mangle]
pub unsafe fn check_pair_to_dst_ref<'a>(x: (usize, usize)) -> &'a [u8] {
// CHECK: %0 = inttoptr i64 %x.0 to ptr
// CHECK: %1 = insertvalue { ptr, i64 } poison, ptr %0, 0
// CHECK: %2 = insertvalue { ptr, i64 } %1, i64 %x.1, 1
// CHECK: ret { ptr, i64 } %2
transmute(x)
}
// CHECK-LABEL: @check_issue_109992(
#[no_mangle]
#[custom_mir(dialect = "runtime", phase = "optimized")]
pub unsafe fn check_issue_109992(x: ()) -> [(); 1] {
// This uses custom MIR to avoid MIR optimizations having removed ZST ops.
// CHECK: start
// CHECK-NEXT: ret void
mir!{
{
RET = CastTransmute(x);
Return()
}
}
}
// CHECK-LABEL: @check_maybe_uninit_pair(i16 %x.0, i64 %x.1)
#[no_mangle]
pub unsafe fn check_maybe_uninit_pair(
x: (MaybeUninit<u16>, MaybeUninit<u64>),
) -> (MaybeUninit<i64>, MaybeUninit<i16>) {
// Thanks to `MaybeUninit` this is actually defined behaviour,
// unlike the examples above with pairs of primitives.
// CHECK: store i16 %x.0
// CHECK: store i64 %x.1
// CHECK: load i64
// CHECK-NOT: noundef
// CHECK: load i16
// CHECK-NOT: noundef
// CHECK: ret { i64, i16 }
transmute(x)
}
#[repr(align(8))]
pub struct HighAlignScalar(u8);
// CHECK-LABEL: @check_to_overalign(
#[no_mangle]
pub unsafe fn check_to_overalign(x: u64) -> HighAlignScalar {
// CHECK: %0 = alloca %HighAlignScalar, align 8
// CHECK: store i64 %x, ptr %0, align 8
// CHECK: %1 = load i64, ptr %0, align 8
// CHECK: ret i64 %1
transmute(x)
}
// CHECK-LABEL: @check_from_overalign(
#[no_mangle]
pub unsafe fn check_from_overalign(x: HighAlignScalar) -> u64 {
// CHECK: %x = alloca %HighAlignScalar, align 8
// CHECK: %[[VAL:.+]] = load i64, ptr %x, align 8
// CHECK: ret i64 %[[VAL]]
transmute(x)
}