Add alignment parameter to simd_masked_{load,store}

compiler/rustc_codegen_cranelift/src/intrinsics/simd.rs

@@ -2,6 +2,7 @@
 
 use cranelift_codegen::ir::immediates::Offset32;
 use rustc_abi::Endian;
+use rustc_middle::ty::SimdAlign;
 
 use super::*;
 use crate::prelude::*;
@@ -960,6 +961,15 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
             let lane_clif_ty = fx.clif_type(val_lane_ty).unwrap();
             let ptr_val = ptr.load_scalar(fx);
 
+            let alignment = generic_args[3].expect_const().to_value().valtree.unwrap_branch()[0]
+                .unwrap_leaf()
+                .to_simd_alignment();
+
+            let memflags = match alignment {
+                SimdAlign::Unaligned => MemFlags::new().with_notrap(),
+                _ => MemFlags::trusted(),
+            };
+
             for lane_idx in 0..val_lane_count {
                 let val_lane = val.value_lane(fx, lane_idx).load_scalar(fx);
                 let mask_lane = mask.value_lane(fx, lane_idx).load_scalar(fx);
@@ -972,7 +982,7 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
 
                 fx.bcx.switch_to_block(if_enabled);
                 let offset = lane_idx as i32 * lane_clif_ty.bytes() as i32;
-                fx.bcx.ins().store(MemFlags::trusted(), val_lane, ptr_val, Offset32::new(offset));
+                fx.bcx.ins().store(memflags, val_lane, ptr_val, Offset32::new(offset));
                 fx.bcx.ins().jump(next, &[]);
 
                 fx.bcx.seal_block(next);
@@ -996,6 +1006,15 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
             let lane_clif_ty = fx.clif_type(val_lane_ty).unwrap();
             let ret_lane_layout = fx.layout_of(ret_lane_ty);
 
+            let alignment = generic_args[3].expect_const().to_value().valtree.unwrap_branch()[0]
+                .unwrap_leaf()
+                .to_simd_alignment();
+
+            let memflags = match alignment {
+                SimdAlign::Unaligned => MemFlags::new().with_notrap(),
+                _ => MemFlags::trusted(),
+            };
+
             for lane_idx in 0..ptr_lane_count {
                 let val_lane = val.value_lane(fx, lane_idx).load_scalar(fx);
                 let ptr_lane = ptr.value_lane(fx, lane_idx).load_scalar(fx);
@@ -1011,7 +1030,7 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
                 fx.bcx.seal_block(if_disabled);
 
                 fx.bcx.switch_to_block(if_enabled);
-                let res = fx.bcx.ins().load(lane_clif_ty, MemFlags::trusted(), ptr_lane, 0);
+                let res = fx.bcx.ins().load(lane_clif_ty, memflags, ptr_lane, 0);
                 fx.bcx.ins().jump(next, &[res.into()]);
 
                 fx.bcx.switch_to_block(if_disabled);

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -13,7 +13,7 @@ use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_hir::{self as hir};
 use rustc_middle::mir::BinOp;
 use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt, HasTypingEnv, LayoutOf};
-use rustc_middle::ty::{self, GenericArgsRef, Instance, Ty, TyCtxt, TypingEnv};
+use rustc_middle::ty::{self, GenericArgsRef, Instance, SimdAlign, Ty, TyCtxt, TypingEnv};
 use rustc_middle::{bug, span_bug};
 use rustc_span::{Span, Symbol, sym};
 use rustc_symbol_mangling::{mangle_internal_symbol, symbol_name_for_instance_in_crate};
@@ -1826,15 +1826,34 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
         ));
     }
 
+    fn llvm_alignment<'ll, 'tcx>(
+        bx: &mut Builder<'_, 'll, 'tcx>,
+        alignment: SimdAlign,
+        vector_ty: Ty<'tcx>,
+        element_ty: Ty<'tcx>,
+    ) -> &'ll Value {
+        let alignment = match alignment {
+            SimdAlign::Unaligned => 1,
+            SimdAlign::Element => bx.align_of(element_ty).bytes(),
+            SimdAlign::Vector => bx.align_of(vector_ty).bytes(),
+        };
+
+        bx.const_i32(alignment as i32)
+    }
+
     if name == sym::simd_masked_load {
-        // simd_masked_load(mask: <N x i{M}>, pointer: *_ T, values: <N x T>) -> <N x T>
+        // simd_masked_load<_, _, _, const ALIGN: SimdAlign>(mask: <N x i{M}>, pointer: *_ T, values: <N x T>) -> <N x T>
         // * N: number of elements in the input vectors
         // * T: type of the element to load
         // * M: any integer width is supported, will be truncated to i1
         // Loads contiguous elements from memory behind `pointer`, but only for
         // those lanes whose `mask` bit is enabled.
         // The memory addresses corresponding to the “off” lanes are not accessed.
 
+        let alignment = fn_args[3].expect_const().to_value().valtree.unwrap_branch()[0]
+            .unwrap_leaf()
+            .to_simd_alignment();
+
         // The element type of the "mask" argument must be a signed integer type of any width
         let mask_ty = in_ty;
         let (mask_len, mask_elem) = (in_len, in_elem);
@@ -1891,7 +1910,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
         let mask = vector_mask_to_bitmask(bx, args[0].immediate(), m_elem_bitwidth, mask_len);
 
         // Alignment of T, must be a constant integer value:
-        let alignment = bx.const_i32(bx.align_of(values_elem).bytes() as i32);
+        let alignment = llvm_alignment(bx, alignment, values_ty, values_elem);
 
         let llvm_pointer = bx.type_ptr();
 
@@ -1906,14 +1925,18 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
     }
 
     if name == sym::simd_masked_store {
-        // simd_masked_store(mask: <N x i{M}>, pointer: *mut T, values: <N x T>) -> ()
+        // simd_masked_store<_, _, _, const ALIGN: SimdAlign>(mask: <N x i{M}>, pointer: *mut T, values: <N x T>) -> ()
         // * N: number of elements in the input vectors
         // * T: type of the element to load
         // * M: any integer width is supported, will be truncated to i1
         // Stores contiguous elements to memory behind `pointer`, but only for
         // those lanes whose `mask` bit is enabled.
         // The memory addresses corresponding to the “off” lanes are not accessed.
 
+        let alignment = fn_args[3].expect_const().to_value().valtree.unwrap_branch()[0]
+            .unwrap_leaf()
+            .to_simd_alignment();
+
         // The element type of the "mask" argument must be a signed integer type of any width
         let mask_ty = in_ty;
         let (mask_len, mask_elem) = (in_len, in_elem);
@@ -1964,7 +1987,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
         let mask = vector_mask_to_bitmask(bx, args[0].immediate(), m_elem_bitwidth, mask_len);
 
         // Alignment of T, must be a constant integer value:
-        let alignment = bx.const_i32(bx.align_of(values_elem).bytes() as i32);
+        let alignment = llvm_alignment(bx, alignment, values_ty, values_elem);
 
         let llvm_pointer = bx.type_ptr();
 

compiler/rustc_const_eval/src/interpret/intrinsics/simd.rs

@@ -1,15 +1,15 @@
 use either::Either;
-use rustc_abi::Endian;
+use rustc_abi::{BackendRepr, Endian};
 use rustc_apfloat::{Float, Round};
-use rustc_middle::mir::interpret::{InterpErrorKind, UndefinedBehaviorInfo};
-use rustc_middle::ty::FloatTy;
+use rustc_middle::mir::interpret::{InterpErrorKind, Pointer, UndefinedBehaviorInfo};
+use rustc_middle::ty::{FloatTy, SimdAlign};
 use rustc_middle::{bug, err_ub_format, mir, span_bug, throw_unsup_format, ty};
 use rustc_span::{Symbol, sym};
 use tracing::trace;
 
 use super::{
-    ImmTy, InterpCx, InterpResult, Machine, OpTy, PlaceTy, Provenance, Scalar, Size, interp_ok,
-    throw_ub_format,
+    ImmTy, InterpCx, InterpResult, Machine, OpTy, PlaceTy, Provenance, Scalar, Size, TyAndLayout,
+    assert_matches, interp_ok, throw_ub_format,
 };
 use crate::interpret::Writeable;
 
@@ -658,6 +658,8 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 }
             }
             sym::simd_masked_load => {
+                let dest_layout = dest.layout;
+
                 let (mask, mask_len) = self.project_to_simd(&args[0])?;
                 let ptr = self.read_pointer(&args[1])?;
                 let (default, default_len) = self.project_to_simd(&args[2])?;
@@ -666,6 +668,14 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 assert_eq!(dest_len, mask_len);
                 assert_eq!(dest_len, default_len);
 
+                self.check_simd_ptr_alignment(
+                    ptr,
+                    dest_layout,
+                    generic_args[3].expect_const().to_value().valtree.unwrap_branch()[0]
+                        .unwrap_leaf()
+                        .to_simd_alignment(),
+                )?;
+
                 for i in 0..dest_len {
                     let mask = self.read_immediate(&self.project_index(&mask, i)?)?;
                     let default = self.read_immediate(&self.project_index(&default, i)?)?;
@@ -674,7 +684,8 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                     let val = if simd_element_to_bool(mask)? {
                         // Size * u64 is implemented as always checked
                         let ptr = ptr.wrapping_offset(dest.layout.size * i, self);
-                        let place = self.ptr_to_mplace(ptr, dest.layout);
+                        // we have already checked the alignment requirements
+                        let place = self.ptr_to_mplace_unaligned(ptr, dest.layout);
                         self.read_immediate(&place)?
                     } else {
                         default
@@ -689,14 +700,23 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
 
                 assert_eq!(mask_len, vals_len);
 
+                self.check_simd_ptr_alignment(
+                    ptr,
+                    args[2].layout,
+                    generic_args[3].expect_const().to_value().valtree.unwrap_branch()[0]
+                        .unwrap_leaf()
+                        .to_simd_alignment(),
+                )?;
+
                 for i in 0..vals_len {
                     let mask = self.read_immediate(&self.project_index(&mask, i)?)?;
                     let val = self.read_immediate(&self.project_index(&vals, i)?)?;
 
                     if simd_element_to_bool(mask)? {
                         // Size * u64 is implemented as always checked
                         let ptr = ptr.wrapping_offset(val.layout.size * i, self);
-                        let place = self.ptr_to_mplace(ptr, val.layout);
+                        // we have already checked the alignment requirements
+                        let place = self.ptr_to_mplace_unaligned(ptr, val.layout);
                         self.write_immediate(*val, &place)?
                     };
                 }
@@ -748,6 +768,29 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             FloatTy::F128 => unimplemented!("f16_f128"),
         })
     }
+
+    fn check_simd_ptr_alignment(
+        &self,
+        ptr: Pointer<Option<M::Provenance>>,
+        vector_layout: TyAndLayout<'tcx>,
+        alignment: SimdAlign,
+    ) -> InterpResult<'tcx> {
+        assert_matches!(vector_layout.backend_repr, BackendRepr::SimdVector { .. });
+
+        match alignment {
+            ty::SimdAlign::Unaligned => {
+                // the pointer is supposed to be unaligned, so no check is required
+                interp_ok(())
+            }
+            ty::SimdAlign::Element => {
+                // take the alignment of the only field, which is an array and therefore has the same alignment
+                // as the element type.
+                let elem_align = vector_layout.field(self, 0).align.abi;
+                self.check_ptr_align(ptr, elem_align)
+            }
+            ty::SimdAlign::Vector => self.check_ptr_align(ptr, vector_layout.align.abi),
+        }
+    }
 }
 
 fn simd_bitmask_index(idx: u32, vec_len: u32, endianness: Endian) -> u32 {

compiler/rustc_hir_analysis/src/check/intrinsic.rs

@@ -695,8 +695,8 @@ pub(crate) fn check_intrinsic_type(
             (1, 0, vec![param(0), param(0), param(0)], param(0))
         }
         sym::simd_gather => (3, 0, vec![param(0), param(1), param(2)], param(0)),
-        sym::simd_masked_load => (3, 0, vec![param(0), param(1), param(2)], param(2)),
-        sym::simd_masked_store => (3, 0, vec![param(0), param(1), param(2)], tcx.types.unit),
+        sym::simd_masked_load => (3, 1, vec![param(0), param(1), param(2)], param(2)),
+        sym::simd_masked_store => (3, 1, vec![param(0), param(1), param(2)], tcx.types.unit),
         sym::simd_scatter => (3, 0, vec![param(0), param(1), param(2)], tcx.types.unit),
         sym::simd_insert | sym::simd_insert_dyn => {
             (2, 0, vec![param(0), tcx.types.u32, param(1)], param(0))

compiler/rustc_middle/src/ty/consts/int.rs

@@ -39,6 +39,15 @@ pub enum AtomicOrdering {
     SeqCst = 4,
 }
 
+/// An enum to represent the compiler-side view of `intrinsics::simd::SimdAlign`.
+#[derive(Debug, Copy, Clone)]
+pub enum SimdAlign {
+    // These values must match `intrinsics::simd::SimdAlign`!
+    Unaligned = 0,
+    Element = 1,
+    Vector = 2,
+}
+
 impl std::fmt::Debug for ConstInt {
     fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let Self { int, signed, is_ptr_sized_integral } = *self;
@@ -350,6 +359,21 @@ impl ScalarInt {
         }
     }
 
+    #[inline]
+    pub fn to_simd_alignment(self) -> SimdAlign {
+        use SimdAlign::*;
+        let val = self.to_u32();
+        if val == Unaligned as u32 {
+            Unaligned
+        } else if val == Element as u32 {
+            Element
+        } else if val == Vector as u32 {
+            Vector
+        } else {
+            panic!("not a valid simd alignment")
+        }
+    }
+
     /// Converts the `ScalarInt` to `bool`.
     /// Panics if the `size` of the `ScalarInt` is not equal to 1 byte.
     /// Errors if it is not a valid `bool`.

compiler/rustc_middle/src/ty/mod.rs

@@ -75,7 +75,7 @@ pub use self::closure::{
 };
 pub use self::consts::{
     AnonConstKind, AtomicOrdering, Const, ConstInt, ConstKind, ConstToValTreeResult, Expr,
-    ExprKind, ScalarInt, UnevaluatedConst, ValTree, ValTreeKind, Value,
+    ExprKind, ScalarInt, SimdAlign, UnevaluatedConst, ValTree, ValTreeKind, Value,
 };
 pub use self::context::{
     CtxtInterners, CurrentGcx, DeducedParamAttrs, Feed, FreeRegionInfo, GlobalCtxt, Lift, TyCtxt,

library/core/src/intrinsics/simd.rs

@@ -2,6 +2,8 @@
 //!
 //! In this module, a "vector" is any `repr(simd)` type.
 
+use crate::marker::ConstParamTy;
+
 /// Inserts an element into a vector, returning the updated vector.
 ///
 /// `T` must be a vector with element type `U`, and `idx` must be `const`.
@@ -377,6 +379,19 @@ pub unsafe fn simd_gather<T, U, V>(val: T, ptr: U, mask: V) -> T;
 #[rustc_nounwind]
 pub unsafe fn simd_scatter<T, U, V>(val: T, ptr: U, mask: V);
 
+/// A type for alignment options for SIMD masked load/store intrinsics.
+#[derive(Debug, ConstParamTy, PartialEq, Eq)]
+pub enum SimdAlign {
+    // These values must match the compiler's `SimdAlign` defined in
+    // `rustc_middle/src/ty/consts/int.rs`!
+    /// No alignment requirements on the pointer
+    Unaligned = 0,
+    /// The pointer must be aligned to the element type of the SIMD vector
+    Element = 1,
+    /// The pointer must be aligned to the SIMD vector type
+    Vector = 2,
+}
+
 /// Reads a vector of pointers.
 ///
 /// `T` must be a vector.
@@ -392,13 +407,12 @@ pub unsafe fn simd_scatter<T, U, V>(val: T, ptr: U, mask: V);
 /// `val`.
 ///
 /// # Safety
-/// Unmasked values in `T` must be readable as if by `<ptr>::read` (e.g. aligned to the element
-/// type).
+/// `ptr` must be aligned according to the `ALIGN` parameter, see [`SimdAlign`] for details.
 ///
 /// `mask` must only contain `0` or `!0` values.
 #[rustc_intrinsic]
 #[rustc_nounwind]
-pub unsafe fn simd_masked_load<V, U, T>(mask: V, ptr: U, val: T) -> T;
+pub unsafe fn simd_masked_load<V, U, T, const ALIGN: SimdAlign>(mask: V, ptr: U, val: T) -> T;
 
 /// Writes to a vector of pointers.
 ///
@@ -414,13 +428,12 @@ pub unsafe fn simd_masked_load<V, U, T>(mask: V, ptr: U, val: T) -> T;
 /// Otherwise if the corresponding value in `mask` is `0`, do nothing.
 ///
 /// # Safety
-/// Unmasked values in `T` must be writeable as if by `<ptr>::write` (e.g. aligned to the element
-/// type).
+/// `ptr` must be aligned according to the `ALIGN` parameter, see [`SimdAlign`] for details.
 ///
 /// `mask` must only contain `0` or `!0` values.
 #[rustc_intrinsic]
 #[rustc_nounwind]
-pub unsafe fn simd_masked_store<V, U, T>(mask: V, ptr: U, val: T);
+pub unsafe fn simd_masked_store<V, U, T, const ALIGN: SimdAlign>(mask: V, ptr: U, val: T);
 
 /// Adds two simd vectors elementwise, with saturation.
 ///