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📁 ..
📄 README.md(8.14 KB)
📄 TODO(950 B)
📄 addressingmodes.go(23.64 KB)
📄 bench_test.go(531 B)
📄 biasedsparsemap.go(2.71 KB)
📄 block.go(11.1 KB)
📄 branchelim.go(11.98 KB)
📄 branchelim_test.go(5.21 KB)
📄 cache.go(2.46 KB)
📄 check.go(16.59 KB)
📄 checkbce.go(956 B)
📄 compile.go(18.19 KB)
📄 config.go(11.7 KB)
📄 copyelim.go(1.83 KB)
📄 copyelim_test.go(1.29 KB)
📄 critical.go(3.19 KB)
📄 cse.go(9.43 KB)
📄 cse_test.go(4.25 KB)
📄 deadcode.go(9.61 KB)
📄 deadcode_test.go(3.49 KB)
📄 deadstore.go(9.08 KB)
📄 deadstore_test.go(4.09 KB)
📄 debug.go(56.34 KB)
📄 debug_lines_test.go(8.29 KB)
📄 debug_test.go(28.75 KB)
📄 decompose.go(13.41 KB)
📄 dom.go(7.98 KB)
📄 dom_test.go(13.34 KB)
📄 expand_calls.go(63.5 KB)
📄 export_test.go(3.23 KB)
📄 flagalloc.go(6.68 KB)
📄 flags_amd64_test.s(533 B)
📄 flags_arm64_test.s(699 B)
📄 flags_test.go(2.49 KB)
📄 func.go(27.08 KB)
📄 func_test.go(13.07 KB)
📄 fuse.go(6.5 KB)
📄 fuse_branchredirect.go(3.24 KB)
📄 fuse_comparisons.go(4.04 KB)
📄 fuse_test.go(7.21 KB)
📁 gen
📄 html.go(34.72 KB)
📄 id.go(576 B)
📄 layout.go(4.82 KB)
📄 lca.go(3.77 KB)
📄 lca_test.go(1.65 KB)
📄 likelyadjust.go(15.24 KB)
📄 location.go(3.06 KB)
📄 loopbce.go(10.54 KB)
📄 loopreschedchecks.go(15.86 KB)
📄 looprotate.go(2.61 KB)
📄 lower.go(1.36 KB)
📄 magic.go(15.77 KB)
📄 magic_test.go(9.1 KB)
📄 nilcheck.go(11.06 KB)
📄 nilcheck_test.go(12.17 KB)
📄 numberlines.go(7.83 KB)
📄 op.go(18.65 KB)
📄 opGen.go(1.01 MB)
📄 opt.go(308 B)
📄 passbm_test.go(3.14 KB)
📄 phielim.go(1.48 KB)
📄 phiopt.go(8.08 KB)
📄 poset.go(37.2 KB)
📄 poset_test.go(18.14 KB)
📄 print.go(3.85 KB)
📄 prove.go(41.82 KB)
📄 regalloc.go(83.69 KB)
📄 regalloc_test.go(6.49 KB)
📄 rewrite.go(53.49 KB)
📄 rewrite386.go(289.01 KB)
📄 rewrite386splitload.go(4.05 KB)
📄 rewriteAMD64.go(888.95 KB)
📄 rewriteAMD64splitload.go(21.41 KB)
📄 rewriteARM.go(487.7 KB)
📄 rewriteARM64.go(751.84 KB)
📄 rewriteCond_test.go(10.62 KB)
📄 rewriteLOONG64.go(193.44 KB)
📄 rewriteMIPS.go(174.44 KB)
📄 rewriteMIPS64.go(195.55 KB)
📄 rewritePPC64.go(431.6 KB)
📄 rewriteRISCV64.go(159.66 KB)
📄 rewriteS390X.go(433.4 KB)
📄 rewriteWasm.go(109.86 KB)
📄 rewrite_test.go(6.91 KB)
📄 rewritedec.go(10.16 KB)
📄 rewritedec64.go(63.77 KB)
📄 rewritegeneric.go(617.96 KB)
📄 schedule.go(18.23 KB)
📄 schedule_test.go(2.91 KB)
📄 shift_test.go(4.05 KB)
📄 shortcircuit.go(12.63 KB)
📄 shortcircuit_test.go(1.31 KB)
📄 sizeof_test.go(855 B)
📄 softfloat.go(1.99 KB)
📄 sparsemap.go(1.98 KB)
📄 sparseset.go(1.54 KB)
📄 sparsetree.go(8.05 KB)
📄 stackalloc.go(12.79 KB)
📄 stackframe.go(290 B)
📄 stmtlines_test.go(2.96 KB)
📁 testdata
📄 tighten.go(4.3 KB)
📄 trim.go(4.24 KB)
📄 tuple.go(1.97 KB)
📄 value.go(15.21 KB)
📄 writebarrier.go(19.29 KB)
📄 writebarrier_test.go(1.75 KB)
📄 xposmap.go(3.29 KB)
📄 zcse.go(2.07 KB)
📄 zeroextension_test.go(1.66 KB)

Editing: layout.go

// Copyright 2015 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 ssa

// layout orders basic blocks in f with the goal of minimizing control flow instructions.
// After this phase returns, the order of f.Blocks matters and is the order
// in which those blocks will appear in the assembly output.
func layout(f *Func) {
	f.Blocks = layoutOrder(f)
}

// Register allocation may use a different order which has constraints
// imposed by the linear-scan algorithm.
func layoutRegallocOrder(f *Func) []*Block {
	// remnant of an experiment; perhaps there will be another.
	return layoutOrder(f)
}

func layoutOrder(f *Func) []*Block {
	order := make([]*Block, 0, f.NumBlocks())
	scheduled := make([]bool, f.NumBlocks())
	idToBlock := make([]*Block, f.NumBlocks())
	indegree := make([]int, f.NumBlocks())
	posdegree := f.newSparseSet(f.NumBlocks()) // blocks with positive remaining degree
	defer f.retSparseSet(posdegree)
	// blocks with zero remaining degree. Use slice to simulate a LIFO queue to implement
	// the depth-first topology sorting algorithm.
	var zerodegree []ID
	// LIFO queue. Track the successor blocks of the scheduled block so that when we
	// encounter loops, we choose to schedule the successor block of the most recently
	// scheduled block.
	var succs []ID
	exit := f.newSparseSet(f.NumBlocks()) // exit blocks
	defer f.retSparseSet(exit)

// Populate idToBlock and find exit blocks.
	for _, b := range f.Blocks {
		idToBlock[b.ID] = b
		if b.Kind == BlockExit {
			exit.add(b.ID)
		}
	}

// Expand exit to include blocks post-dominated by exit blocks.
	for {
		changed := false
		for _, id := range exit.contents() {
			b := idToBlock[id]
		NextPred:
			for _, pe := range b.Preds {
				p := pe.b
				if exit.contains(p.ID) {
					continue
				}
				for _, s := range p.Succs {
					if !exit.contains(s.b.ID) {
						continue NextPred
					}
				}
				// All Succs are in exit; add p.
				exit.add(p.ID)
				changed = true
			}
		}
		if !changed {
			break
		}
	}

// Initialize indegree of each block
	for _, b := range f.Blocks {
		if exit.contains(b.ID) {
			// exit blocks are always scheduled last
			continue
		}
		indegree[b.ID] = len(b.Preds)
		if len(b.Preds) == 0 {
			// Push an element to the tail of the queue.
			zerodegree = append(zerodegree, b.ID)
		} else {
			posdegree.add(b.ID)
		}
	}

bid := f.Entry.ID
blockloop:
	for {
		// add block to schedule
		b := idToBlock[bid]
		order = append(order, b)
		scheduled[bid] = true
		if len(order) == len(f.Blocks) {
			break
		}

// Here, the order of traversing the b.Succs affects the direction in which the topological
		// sort advances in depth. Take the following cfg as an example, regardless of other factors.
		//           b1
		//         0/ \1
		//        b2   b3
		// Traverse b.Succs in order, the right child node b3 will be scheduled immediately after
		// b1, traverse b.Succs in reverse order, the left child node b2 will be scheduled
		// immediately after b1. The test results show that reverse traversal performs a little
		// better.
		// Note: You need to consider both layout and register allocation when testing performance.
		for i := len(b.Succs) - 1; i >= 0; i-- {
			c := b.Succs[i].b
			indegree[c.ID]--
			if indegree[c.ID] == 0 {
				posdegree.remove(c.ID)
				zerodegree = append(zerodegree, c.ID)
			} else {
				succs = append(succs, c.ID)
			}
		}

// Pick the next block to schedule
		// Pick among the successor blocks that have not been scheduled yet.

// Use likely direction if we have it.
		var likely *Block
		switch b.Likely {
		case BranchLikely:
			likely = b.Succs[0].b
		case BranchUnlikely:
			likely = b.Succs[1].b
		}
		if likely != nil && !scheduled[likely.ID] {
			bid = likely.ID
			continue
		}

// Use degree for now.
		bid = 0
		// TODO: improve this part
		// No successor of the previously scheduled block works.
		// Pick a zero-degree block if we can.
		for len(zerodegree) > 0 {
			// Pop an element from the tail of the queue.
			cid := zerodegree[len(zerodegree)-1]
			zerodegree = zerodegree[:len(zerodegree)-1]
			if !scheduled[cid] {
				bid = cid
				continue blockloop
			}
		}

// Still nothing, pick the unscheduled successor block encountered most recently.
		for len(succs) > 0 {
			// Pop an element from the tail of the queue.
			cid := succs[len(succs)-1]
			succs = succs[:len(succs)-1]
			if !scheduled[cid] {
				bid = cid
				continue blockloop
			}
		}

// Still nothing, pick any non-exit block.
		for posdegree.size() > 0 {
			cid := posdegree.pop()
			if !scheduled[cid] {
				bid = cid
				continue blockloop
			}
		}
		// Pick any exit block.
		// TODO: Order these to minimize jump distances?
		for {
			cid := exit.pop()
			if !scheduled[cid] {
				bid = cid
				continue blockloop
			}
		}
	}
	f.laidout = true
	return order
	//f.Blocks = order
}

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Editing: layout.go

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