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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)
+}