rust/compiler/rustc_codegen_ssa/src/traits/builder.rs

use super::abi::AbiBuilderMethods;
use super::asm::AsmBuilderMethods;
use super::consts::ConstMethods;
use super::coverageinfo::CoverageInfoBuilderMethods;
use super::debuginfo::DebugInfoBuilderMethods;
use super::intrinsic::IntrinsicCallMethods;
use super::misc::MiscMethods;
use super::type_::{ArgAbiMethods, BaseTypeMethods};
use super::{HasCodegen, StaticBuilderMethods};

use crate::common::{
    AtomicOrdering, AtomicRmwBinOp, IntPredicate, RealPredicate, SynchronizationScope, TypeKind,
};
use crate::mir::operand::OperandRef;
use crate::mir::place::PlaceRef;
use crate::MemFlags;

use rustc_apfloat::{ieee, Float, Round, Status};
use rustc_middle::ty::layout::{HasParamEnv, TyAndLayout};
use rustc_middle::ty::Ty;
use rustc_span::Span;
use rustc_target::abi::{Abi, Align, Scalar, Size, WrappingRange};
use rustc_target::spec::HasTargetSpec;

#[derive(Copy, Clone)]
pub enum OverflowOp {
    Add,
    Sub,
    Mul,
}

pub trait BuilderMethods<'a, 'tcx>:
    HasCodegen<'tcx>
    + CoverageInfoBuilderMethods<'tcx>
    + DebugInfoBuilderMethods
    + ArgAbiMethods<'tcx>
    + AbiBuilderMethods<'tcx>
    + IntrinsicCallMethods<'tcx>
    + AsmBuilderMethods<'tcx>
    + StaticBuilderMethods
    + HasParamEnv<'tcx>
    + HasTargetSpec
{
    fn build(cx: &'a Self::CodegenCx, llbb: Self::BasicBlock) -> Self;

    fn cx(&self) -> &Self::CodegenCx;
    fn llbb(&self) -> Self::BasicBlock;

    fn set_span(&mut self, span: Span);

    // FIXME(eddyb) replace uses of this with `append_sibling_block`.
    fn append_block(cx: &'a Self::CodegenCx, llfn: Self::Function, name: &str) -> Self::BasicBlock;

    fn append_sibling_block(&mut self, name: &str) -> Self::BasicBlock;

    // FIXME(eddyb) replace with callers using `append_sibling_block`.
    fn build_sibling_block(&mut self, name: &str) -> Self;

    fn ret_void(&mut self);
    fn ret(&mut self, v: Self::Value);
    fn br(&mut self, dest: Self::BasicBlock);
    fn cond_br(
        &mut self,
        cond: Self::Value,
        then_llbb: Self::BasicBlock,
        else_llbb: Self::BasicBlock,
    );
    fn switch(
        &mut self,
        v: Self::Value,
        else_llbb: Self::BasicBlock,
        cases: impl ExactSizeIterator<Item = (u128, Self::BasicBlock)>,
    );
    fn invoke(
        &mut self,
        llty: Self::Type,
        llfn: Self::Value,
        args: &[Self::Value],
        then: Self::BasicBlock,
        catch: Self::BasicBlock,
        funclet: Option<&Self::Funclet>,
    ) -> Self::Value;
    fn unreachable(&mut self);

    fn add(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn fadd(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn fadd_fast(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn sub(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn fsub(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn fsub_fast(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn mul(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn fmul(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn fmul_fast(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn udiv(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn exactudiv(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn sdiv(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn exactsdiv(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn fdiv(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn fdiv_fast(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn urem(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn srem(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn frem(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn frem_fast(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn shl(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn lshr(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn ashr(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn unchecked_sadd(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn unchecked_uadd(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn unchecked_ssub(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn unchecked_usub(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn unchecked_smul(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn unchecked_umul(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn and(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn or(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn xor(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn neg(&mut self, v: Self::Value) -> Self::Value;
    fn fneg(&mut self, v: Self::Value) -> Self::Value;
    fn not(&mut self, v: Self::Value) -> Self::Value;

    fn checked_binop(
        &mut self,
        oop: OverflowOp,
        ty: Ty<'_>,
        lhs: Self::Value,
        rhs: Self::Value,
    ) -> (Self::Value, Self::Value);

    fn from_immediate(&mut self, val: Self::Value) -> Self::Value;
    fn to_immediate(&mut self, val: Self::Value, layout: TyAndLayout<'_>) -> Self::Value {
        if let Abi::Scalar(scalar) = layout.abi {
            self.to_immediate_scalar(val, scalar)
        } else {
            val
        }
    }
    fn to_immediate_scalar(&mut self, val: Self::Value, scalar: Scalar) -> Self::Value;

    fn alloca(&mut self, ty: Self::Type, align: Align) -> Self::Value;
    fn dynamic_alloca(&mut self, ty: Self::Type, align: Align) -> Self::Value;
    fn array_alloca(&mut self, ty: Self::Type, len: Self::Value, align: Align) -> Self::Value;

    fn load(&mut self, ty: Self::Type, ptr: Self::Value, align: Align) -> Self::Value;
    fn volatile_load(&mut self, ty: Self::Type, ptr: Self::Value) -> Self::Value;
    fn atomic_load(
        &mut self,
        ty: Self::Type,
        ptr: Self::Value,
        order: AtomicOrdering,
        size: Size,
    ) -> Self::Value;
    fn load_operand(&mut self, place: PlaceRef<'tcx, Self::Value>)
    -> OperandRef<'tcx, Self::Value>;

    /// Called for Rvalue::Repeat when the elem is neither a ZST nor optimizable using memset.
    fn write_operand_repeatedly(
        self,
        elem: OperandRef<'tcx, Self::Value>,
        count: u64,
        dest: PlaceRef<'tcx, Self::Value>,
    ) -> Self;

    fn range_metadata(&mut self, load: Self::Value, range: WrappingRange);
    fn nonnull_metadata(&mut self, load: Self::Value);
    fn type_metadata(&mut self, function: Self::Function, typeid: String);
    fn typeid_metadata(&mut self, typeid: String) -> Self::Value;

    fn store(&mut self, val: Self::Value, ptr: Self::Value, align: Align) -> Self::Value;
    fn store_with_flags(
        &mut self,
        val: Self::Value,
        ptr: Self::Value,
        align: Align,
        flags: MemFlags,
    ) -> Self::Value;
    fn atomic_store(
        &mut self,
        val: Self::Value,
        ptr: Self::Value,
        order: AtomicOrdering,
        size: Size,
    );

    fn gep(&mut self, ty: Self::Type, ptr: Self::Value, indices: &[Self::Value]) -> Self::Value;
    fn inbounds_gep(
        &mut self,
        ty: Self::Type,
        ptr: Self::Value,
        indices: &[Self::Value],
    ) -> Self::Value;
    fn struct_gep(&mut self, ty: Self::Type, ptr: Self::Value, idx: u64) -> Self::Value;

    fn trunc(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
    fn sext(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
    fn fptoui_sat(&mut self, val: Self::Value, dest_ty: Self::Type) -> Option<Self::Value>;
    fn fptosi_sat(&mut self, val: Self::Value, dest_ty: Self::Type) -> Option<Self::Value>;
    fn fptoui(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
    fn fptosi(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
    fn uitofp(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
    fn sitofp(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
    fn fptrunc(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
    fn fpext(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
    fn ptrtoint(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
    fn inttoptr(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
    fn bitcast(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
    fn intcast(&mut self, val: Self::Value, dest_ty: Self::Type, is_signed: bool) -> Self::Value;
    fn pointercast(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;

    fn cast_float_to_int(
        &mut self,
        signed: bool,
        x: Self::Value,
        dest_ty: Self::Type,
    ) -> Self::Value {
        let in_ty = self.cx().val_ty(x);
        let (float_ty, int_ty) = if self.cx().type_kind(dest_ty) == TypeKind::Vector
            && self.cx().type_kind(in_ty) == TypeKind::Vector
        {
            (self.cx().element_type(in_ty), self.cx().element_type(dest_ty))
        } else {
            (in_ty, dest_ty)
        };
        assert!(matches!(self.cx().type_kind(float_ty), TypeKind::Float | TypeKind::Double));
        assert_eq!(self.cx().type_kind(int_ty), TypeKind::Integer);

        if let Some(false) = self.cx().sess().opts.debugging_opts.saturating_float_casts {
            return if signed { self.fptosi(x, dest_ty) } else { self.fptoui(x, dest_ty) };
        }

        let try_sat_result =
            if signed { self.fptosi_sat(x, dest_ty) } else { self.fptoui_sat(x, dest_ty) };
        if let Some(try_sat_result) = try_sat_result {
            return try_sat_result;
        }

        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(x, dest_ty) } else { self.fptoui(x, dest_ty) };
        let less_or_nan = self.fcmp(RealPredicate::RealULT, x, f_min);
        let greater = self.fcmp(RealPredicate::RealOGT, x, 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, x, x);
            self.select(cmp, s1, zero)
        } else {
            s1
        }
    }

    fn icmp(&mut self, op: IntPredicate, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
    fn fcmp(&mut self, op: RealPredicate, lhs: Self::Value, rhs: Self::Value) -> Self::Value;

    fn memcpy(
        &mut self,
        dst: Self::Value,
        dst_align: Align,
        src: Self::Value,
        src_align: Align,
        size: Self::Value,
        flags: MemFlags,
    );
    fn memmove(
        &mut self,
        dst: Self::Value,
        dst_align: Align,
        src: Self::Value,
        src_align: Align,
        size: Self::Value,
        flags: MemFlags,
    );
    fn memset(
        &mut self,
        ptr: Self::Value,
        fill_byte: Self::Value,
        size: Self::Value,
        align: Align,
        flags: MemFlags,
    );

    fn select(
        &mut self,
        cond: Self::Value,
        then_val: Self::Value,
        else_val: Self::Value,
    ) -> Self::Value;

    fn va_arg(&mut self, list: Self::Value, ty: Self::Type) -> Self::Value;
    fn extract_element(&mut self, vec: Self::Value, idx: Self::Value) -> Self::Value;
    fn vector_splat(&mut self, num_elts: usize, elt: Self::Value) -> Self::Value;
    fn extract_value(&mut self, agg_val: Self::Value, idx: u64) -> Self::Value;
    fn insert_value(&mut self, agg_val: Self::Value, elt: Self::Value, idx: u64) -> Self::Value;

    fn set_personality_fn(&mut self, personality: Self::Value);

    // These are used by everyone except msvc
    fn landing_pad(
        &mut self,
        ty: Self::Type,
        pers_fn: Self::Value,
        num_clauses: usize,
    ) -> Self::Value;
    fn set_cleanup(&mut self, landing_pad: Self::Value);
    fn resume(&mut self, exn: Self::Value);

    // These are used only by msvc
    fn cleanup_pad(&mut self, parent: Option<Self::Value>, args: &[Self::Value]) -> Self::Funclet;
    fn cleanup_ret(&mut self, funclet: &Self::Funclet, unwind: Option<Self::BasicBlock>);
    fn catch_pad(&mut self, parent: Self::Value, args: &[Self::Value]) -> Self::Funclet;
    fn catch_switch(
        &mut self,
        parent: Option<Self::Value>,
        unwind: Option<Self::BasicBlock>,
        handlers: &[Self::BasicBlock],
    ) -> Self::Value;

    fn atomic_cmpxchg(
        &mut self,
        dst: Self::Value,
        cmp: Self::Value,
        src: Self::Value,
        order: AtomicOrdering,
        failure_order: AtomicOrdering,
        weak: bool,
    ) -> Self::Value;
    fn atomic_rmw(
        &mut self,
        op: AtomicRmwBinOp,
        dst: Self::Value,
        src: Self::Value,
        order: AtomicOrdering,
    ) -> Self::Value;
    fn atomic_fence(&mut self, order: AtomicOrdering, scope: SynchronizationScope);
    fn set_invariant_load(&mut self, load: Self::Value);

    /// Called for `StorageLive`
    fn lifetime_start(&mut self, ptr: Self::Value, size: Size);

    /// Called for `StorageDead`
    fn lifetime_end(&mut self, ptr: Self::Value, size: Size);

    fn instrprof_increment(
        &mut self,
        fn_name: Self::Value,
        hash: Self::Value,
        num_counters: Self::Value,
        index: Self::Value,
    );

    fn call(
        &mut self,
        llty: Self::Type,
        llfn: Self::Value,
        args: &[Self::Value],
        funclet: Option<&Self::Funclet>,
    ) -> Self::Value;
    fn zext(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;

    fn apply_attrs_to_cleanup_callsite(&mut self, llret: Self::Value);
}