github.com/shogo82148/std@v1.22.1-0.20240327122250-4e474527810c/cmd/internal/obj/s390x/rotate.go (about)

     1  // Copyright 2019 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package s390x
     6  
     7  // RotateParams represents the immediates required for a "rotate
     8  // then ... selected bits instruction".
     9  //
    10  // The Start and End values are the indexes that represent
    11  // the masked region. They are inclusive and are in big-
    12  // endian order (bit 0 is the MSB, bit 63 is the LSB). They
    13  // may wrap around.
    14  //
    15  // Some examples:
    16  //
    17  // Masked region             | Start | End
    18  // --------------------------+-------+----
    19  // 0x00_00_00_00_00_00_00_0f | 60    | 63
    20  // 0xf0_00_00_00_00_00_00_00 | 0     | 3
    21  // 0xf0_00_00_00_00_00_00_0f | 60    | 3
    22  //
    23  // The Amount value represents the amount to rotate the
    24  // input left by. Note that this rotation is performed
    25  // before the masked region is used.
    26  type RotateParams struct {
    27  	Start  uint8
    28  	End    uint8
    29  	Amount uint8
    30  }
    31  
    32  // NewRotateParams creates a set of parameters representing a
    33  // rotation left by the amount provided and a selection of the bits
    34  // between the provided start and end indexes (inclusive).
    35  //
    36  // The start and end indexes and the rotation amount must all
    37  // be in the range 0-63 inclusive or this function will panic.
    38  func NewRotateParams(start, end, amount uint8) RotateParams
    39  
    40  // RotateLeft generates a new set of parameters with the rotation amount
    41  // increased by the given value. The selected bits are left unchanged.
    42  func (r RotateParams) RotateLeft(amount uint8) RotateParams
    43  
    44  // OutMask provides a mask representing the selected bits.
    45  func (r RotateParams) OutMask() uint64
    46  
    47  // InMask provides a mask representing the selected bits relative
    48  // to the source value (i.e. pre-rotation).
    49  func (r RotateParams) InMask() uint64
    50  
    51  // OutMerge tries to generate a new set of parameters representing
    52  // the intersection between the selected bits and the provided mask.
    53  // If the intersection is unrepresentable (0 or not contiguous) nil
    54  // will be returned.
    55  func (r RotateParams) OutMerge(mask uint64) *RotateParams
    56  
    57  // InMerge tries to generate a new set of parameters representing
    58  // the intersection between the selected bits and the provided mask
    59  // as applied to the source value (i.e. pre-rotation).
    60  // If the intersection is unrepresentable (0 or not contiguous) nil
    61  // will be returned.
    62  func (r RotateParams) InMerge(mask uint64) *RotateParams
    63  
    64  func (RotateParams) CanBeAnSSAAux()