Function load_heap_addr_checked

winch/codegen/src/codegen/bounds.rs:155–188

Performs the out-of-bounds check and returns the heap address if the access criteria is in bounds.

(
    masm: &mut M,
    context: &mut CodeGenContext<Emission>,
    ptr_size: OperandSize,
    heap: &HeapData,
    enable_spectre_mitigation: bool,
    bounds: Bounds,
    index: Index,
    offset: I

/// Performs the out-of-bounds check and returns the heap address if the access
/// criteria is in bounds.
pub(crate) fn load_heap_addr_checked<M, F>(
    masm: &mut M,
    context: &mut CodeGenContext<Emission>,
    ptr_size: OperandSize,
    heap: &HeapData,
    enable_spectre_mitigation: bool,
    bounds: Bounds,
    index: Index,
    offset: ImmOffset,
    mut emit_check_condition: F,
) -> Result<Reg>
where
    M: MacroAssembler,
    F: FnMut(&mut M, Bounds, Index) -> Result<IntCmpKind>,
{
    let cmp_kind = emit_check_condition(masm, bounds, index)?;

    masm.trapif(cmp_kind, TrapCode::HEAP_OUT_OF_BOUNDS)?;
    let addr = context.any_gpr(masm)?;

    load_heap_addr_unchecked(masm, heap, index, offset, addr, ptr_size)?;
    if !enable_spectre_mitigation {
        Ok(addr)
    } else {
        // Conditionally assign 0 to the register holding the base address if
        // the comparison kind is met.
        let tmp = context.any_gpr(masm)?;
        masm.mov(writable!(tmp), RegImm::i64(0), ptr_size)?;
        let cmp_kind = emit_check_condition(masm, bounds, index)?;
        masm.cmov(writable!(addr), tmp, cmp_kind, ptr_size)?;
        context.free_reg(tmp);
        Ok(addr)
    }
}

/// Load the requested heap address into the specified destination register.
/// This function doesn't perform any bounds checks and assumes the caller