127 lines
3.1 KiB
Go
127 lines
3.1 KiB
Go
// 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)
|
|
}
|