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// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package s390x
import (
"fmt"
)
// CCMask represents a 4-bit condition code mask. Bits that
// are not part of the mask should be 0.
//
// Condition code masks represent the 4 possible values of
// the 2-bit condition code as individual bits. Since IBM Z
// is a big-endian platform bits are numbered from left to
// right. The lowest value, 0, is represented by 8 (0b1000)
// and the highest value, 3, is represented by 1 (0b0001).
//
// Note that condition code values have different semantics
// depending on the instruction that set the condition code.
// The names given here assume that the condition code was
// set by an integer or floating point comparison. Other
// instructions may use these same codes to indicate
// different results such as a carry or overflow.
type CCMask uint8
const (
Never CCMask = 0 // no-op
// 1-bit masks
Equal CCMask = 1 << 3
Less CCMask = 1 << 2
Greater CCMask = 1 << 1
Unordered CCMask = 1 << 0
// 2-bit masks
EqualOrUnordered CCMask = Equal | Unordered // not less and not greater
LessOrEqual CCMask = Less | Equal // ordered and not greater
LessOrGreater CCMask = Less | Greater // ordered and not equal
LessOrUnordered CCMask = Less | Unordered // not greater and not equal
GreaterOrEqual CCMask = Greater | Equal // ordered and not less
GreaterOrUnordered CCMask = Greater | Unordered // not less and not equal
// 3-bit masks
NotEqual CCMask = Always ^ Equal
NotLess CCMask = Always ^ Less
NotGreater CCMask = Always ^ Greater
NotUnordered CCMask = Always ^ Unordered
// 4-bit mask
Always CCMask = Equal | Less | Greater | Unordered
// useful aliases
Carry CCMask = GreaterOrUnordered
NoCarry CCMask = LessOrEqual
Borrow CCMask = NoCarry
NoBorrow CCMask = Carry
)
// Inverse returns the complement of the condition code mask.
func (c CCMask) Inverse() CCMask {
return c ^ Always
}
// ReverseComparison swaps the bits at 0b0100 and 0b0010 in the mask,
// reversing the behavior of greater than and less than conditions.
func (c CCMask) ReverseComparison() CCMask {
r := c & EqualOrUnordered
if c&Less != 0 {
r |= Greater
}
if c&Greater != 0 {
r |= Less
}
return r
}
func (c CCMask) String() string {
switch c {
// 0-bit mask
case Never:
return "Never"
// 1-bit masks
case Equal:
return "Equal"
case Less:
return "Less"
case Greater:
return "Greater"
case Unordered:
return "Unordered"
// 2-bit masks
case EqualOrUnordered:
return "EqualOrUnordered"
case LessOrEqual:
return "LessOrEqual"
case LessOrGreater:
return "LessOrGreater"
case LessOrUnordered:
return "LessOrUnordered"
case GreaterOrEqual:
return "GreaterOrEqual"
case GreaterOrUnordered:
return "GreaterOrUnordered"
// 3-bit masks
case NotEqual:
return "NotEqual"
case NotLess:
return "NotLess"
case NotGreater:
return "NotGreater"
case NotUnordered:
return "NotUnordered"
// 4-bit mask
case Always:
return "Always"
}
// invalid
return fmt.Sprintf("Invalid (%#x)", c)
}
func (CCMask) CanBeAnSSAAux() {}
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