github.com/mh-cbon/go@v0.0.0-20160603070303-9e112a3fe4c0/src/cmd/compile/internal/ssa/trim.go (about)

     1  // Copyright 2016 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 ssa
     6  
     7  // trim removes blocks with no code in them.
     8  // These blocks were inserted to remove critical edges.
     9  func trim(f *Func) {
    10  	n := 0
    11  	for _, b := range f.Blocks {
    12  		if b.Kind != BlockPlain || len(b.Values) != 0 || len(b.Preds) != 1 {
    13  			f.Blocks[n] = b
    14  			n++
    15  			continue
    16  		}
    17  		// TODO: handle len(b.Preds)>1 case.
    18  
    19  		// Splice b out of the graph.
    20  		p := b.Preds[0].b
    21  		i := b.Preds[0].i
    22  		s := b.Succs[0].b
    23  		j := b.Succs[0].i
    24  		p.Succs[i] = Edge{s, j}
    25  		s.Preds[j] = Edge{p, i}
    26  	}
    27  	tail := f.Blocks[n:]
    28  	for i := range tail {
    29  		tail[i] = nil
    30  	}
    31  	f.Blocks = f.Blocks[:n]
    32  }