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Source file src/cmd/internal/obj/inl.go

Documentation: cmd/internal/obj

     1  // Copyright 2017 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 obj
     6  
     7  import "cmd/internal/src"
     8  
     9  // InlTree is a collection of inlined calls. The Parent field of an
    10  // InlinedCall is the index of another InlinedCall in InlTree.
    11  //
    12  // The compiler maintains a global inlining tree and adds a node to it
    13  // every time a function is inlined. For example, suppose f() calls g()
    14  // and g has two calls to h(), and that f, g, and h are inlineable:
    15  //
    16  //  1 func main() {
    17  //  2     f()
    18  //  3 }
    19  //  4 func f() {
    20  //  5     g()
    21  //  6 }
    22  //  7 func g() {
    23  //  8     h()
    24  //  9     h()
    25  // 10 }
    26  // 11 func h() {
    27  // 12     println("H")
    28  // 13 }
    29  //
    30  // Assuming the global tree starts empty, inlining will produce the
    31  // following tree:
    32  //
    33  //   []InlinedCall{
    34  //     {Parent: -1, Func: "f", Pos: <line 2>},
    35  //     {Parent:  0, Func: "g", Pos: <line 5>},
    36  //     {Parent:  1, Func: "h", Pos: <line 8>},
    37  //     {Parent:  1, Func: "h", Pos: <line 9>},
    38  //   }
    39  //
    40  // The nodes of h inlined into main will have inlining indexes 2 and 3.
    41  //
    42  // Eventually, the compiler extracts a per-function inlining tree from
    43  // the global inlining tree (see pcln.go).
    44  type InlTree struct {
    45  	nodes []InlinedCall
    46  }
    47  
    48  // InlinedCall is a node in an InlTree.
    49  type InlinedCall struct {
    50  	Parent int      // index of the parent in the InlTree or < 0 if outermost call
    51  	Pos    src.XPos // position of the inlined call
    52  	Func   *LSym    // function that was inlined
    53  }
    54  
    55  // Add adds a new call to the tree, returning its index.
    56  func (tree *InlTree) Add(parent int, pos src.XPos, func_ *LSym) int {
    57  	r := len(tree.nodes)
    58  	call := InlinedCall{
    59  		Parent: parent,
    60  		Pos:    pos,
    61  		Func:   func_,
    62  	}
    63  	tree.nodes = append(tree.nodes, call)
    64  	return r
    65  }
    66  
    67  func (tree *InlTree) Parent(inlIndex int) int {
    68  	return tree.nodes[inlIndex].Parent
    69  }
    70  
    71  func (tree *InlTree) InlinedFunction(inlIndex int) *LSym {
    72  	return tree.nodes[inlIndex].Func
    73  }
    74  
    75  func (tree *InlTree) CallPos(inlIndex int) src.XPos {
    76  	return tree.nodes[inlIndex].Pos
    77  }
    78  
    79  // OutermostPos returns the outermost position corresponding to xpos,
    80  // which is where xpos was ultimately inlined to. In the example for
    81  // InlTree, main() contains inlined AST nodes from h(), but the
    82  // outermost position for those nodes is line 2.
    83  func (ctxt *Link) OutermostPos(xpos src.XPos) src.Pos {
    84  	pos := ctxt.InnermostPos(xpos)
    85  
    86  	outerxpos := xpos
    87  	for ix := pos.Base().InliningIndex(); ix >= 0; {
    88  		call := ctxt.InlTree.nodes[ix]
    89  		ix = call.Parent
    90  		outerxpos = call.Pos
    91  	}
    92  	return ctxt.PosTable.Pos(outerxpos)
    93  }
    94  
    95  // InnermostPos returns the innermost position corresponding to xpos,
    96  // that is, the code that is inlined and that inlines nothing else.
    97  // In the example for InlTree above, the code for println within h
    98  // would have an innermost position with line number 12, whether
    99  // h was not inlined, inlined into g, g-then-f, or g-then-f-then-main.
   100  // This corresponds to what someone debugging main, f, g, or h might
   101  // expect to see while single-stepping.
   102  func (ctxt *Link) InnermostPos(xpos src.XPos) src.Pos {
   103  	return ctxt.PosTable.Pos(xpos)
   104  }
   105  
   106  func dumpInlTree(ctxt *Link, tree InlTree) {
   107  	for i, call := range tree.nodes {
   108  		pos := ctxt.PosTable.Pos(call.Pos)
   109  		ctxt.Logf("%0d | %0d | %s (%s)\n", i, call.Parent, call.Func, pos)
   110  	}
   111  }
   112  

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