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48 lines
1.3 KiB
Go
48 lines
1.3 KiB
Go
// Copyright 2019 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package s390x
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// RotateParams represents the immediates required for a "rotate
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// then ... selected bits instruction".
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//
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// The Start and End values are the indexes that represent
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// the masked region. They are inclusive and are in big-
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// endian order (bit 0 is the MSB, bit 63 is the LSB). They
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// may wrap around.
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//
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// Some examples:
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//
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// Masked region | Start | End
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// --------------------------+-------+----
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// 0x00_00_00_00_00_00_00_0f | 60 | 63
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// 0xf0_00_00_00_00_00_00_00 | 0 | 3
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// 0xf0_00_00_00_00_00_00_0f | 60 | 3
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//
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// The Amount value represents the amount to rotate the
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// input left by. Note that this rotation is performed
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// before the masked region is used.
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type RotateParams struct {
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Start uint8 // big-endian start bit index [0..63]
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End uint8 // big-endian end bit index [0..63]
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Amount uint8 // amount to rotate left
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}
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func NewRotateParams(start, end, amount int64) RotateParams {
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if start&^63 != 0 {
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panic("start out of bounds")
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}
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if end&^63 != 0 {
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panic("end out of bounds")
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}
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if amount&^63 != 0 {
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panic("amount out of bounds")
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}
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return RotateParams{
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Start: uint8(start),
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End: uint8(end),
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Amount: uint8(amount),
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}
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}
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