masks.go

     1  // Copyright 2026 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 spec
     6  
     7  // UintN represents a Go uintN type. An argument x of type UintN introduces a
     8  // constraint variable named xN that must be resolved to the bit width (8, 16,
     9  // 32, or 64). Widths smaller than 8 are rounded up to 8. Widths larger than 64
    10  // are not allowed.
    11  //
    12  // This is used by mask operations that convert between bits in a uintN type and
    13  // elements in a mask.
    14  //
    15  // This type is known to specgen.
    16  type UintN uint64
    17  
    18  // MaskFromBits constructs a mask from a bitmap value. If bit i of y is set,
    19  // then mask element i of the result is set.
    20  //
    21  //specgen:name {z}FromBits
    22  //specgen:require x=uint{zL}
    23  func MaskFromBits[E MaskElt, W FixedWidth](x UintN) (z Vec[E, W]) {
    24  	z = makeVec[E, W]()
    25  	for i := range z {
    26  		if x&(1<<i) != 0 {
    27  			z[i] = 1
    28  		}
    29  	}
    30  	return z
    31  }
    32  
    33  // MaskToBits constructs a bitmap from mask x, where bit i is set if mask
    34  // element i is set.
    35  //
    36  //specgen:name ToBits
    37  //specgen:require z=uint{xL}
    38  func MaskToBits[E MaskElt, W FixedWidth](x Vec[E, W]) (z UintN) {
    39  	for i, elt := range x {
    40  		if elt != 0 {
    41  			z |= 1 << i
    42  		}
    43  	}
    44  	return z
    45  }
    46  
    47  // MaskToZ converts the mask to a vector, where element i is set to ^0 (all bits
    48  // set, e.g., -1) if mask element i is "true".
    49  //
    50  //specgen:name To{z}
    51  //specgen:require z=Int{xN}x{xL}
    52  func MaskToZ[E MaskElt, W Width, zE Ints](x Vec[E, W]) (z Vec[zE, W]) {
    53  	z = makeVec[zE, W]()
    54  	for i, val := range x {
    55  		if val != 0 {
    56  			z[i] = ^0
    57  		}
    58  	}
    59  	return z
    60  }
    61
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