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opt / golang / 1.19.4 / src / cmd / compile / internal / ssa /

📁 ..
📄 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: fuse_branchredirect.go

// Copyright 2021 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

// fuseBranchRedirect checks for a CFG in which the outbound branch
// of an If block can be derived from its predecessor If block, in
// some such cases, we can redirect the predecessor If block to the
// corresponding successor block directly. For example:
//
//	p:
//	  v11 = Less64 <bool> v10 v8
//	  If v11 goto b else u
//	b: <- p ...
//	  v17 = Leq64 <bool> v10 v8
//	  If v17 goto s else o
//
// We can redirect p to s directly.
//
// The implementation here borrows the framework of the prove pass.
//
//	1, Traverse all blocks of function f to find If blocks.
//	2,   For any If block b, traverse all its predecessors to find If blocks.
//	3,     For any If block predecessor p, update relationship p->b.
//	4,     Traverse all successors of b.
//	5,       For any successor s of b, try to update relationship b->s, if a
//	         contradiction is found then redirect p to another successor of b.
func fuseBranchRedirect(f *Func) bool {
	ft := newFactsTable(f)
	ft.checkpoint()

changed := false
	for i := len(f.Blocks) - 1; i >= 0; i-- {
		b := f.Blocks[i]
		if b.Kind != BlockIf {
			continue
		}
		// b is either empty or only contains the control value.
		// TODO: if b contains only OpCopy or OpNot related to b.Controls,
		// such as Copy(Not(Copy(Less64(v1, v2)))), perhaps it can be optimized.
		bCtl := b.Controls[0]
		if bCtl.Block != b && len(b.Values) != 0 || (len(b.Values) != 1 || bCtl.Uses != 1) && bCtl.Block == b {
			continue
		}

for k := 0; k < len(b.Preds); k++ {
			pk := b.Preds[k]
			p := pk.b
			if p.Kind != BlockIf || p == b {
				continue
			}
			pbranch := positive
			if pk.i == 1 {
				pbranch = negative
			}
			ft.checkpoint()
			// Assume branch p->b is taken.
			addBranchRestrictions(ft, p, pbranch)
			// Check if any outgoing branch is unreachable based on the above condition.
			parent := b
			for j, bbranch := range [...]branch{positive, negative} {
				ft.checkpoint()
				// Try to update relationship b->child, and check if the contradiction occurs.
				addBranchRestrictions(ft, parent, bbranch)
				unsat := ft.unsat
				ft.restore()
				if !unsat {
					continue
				}
				// This branch is impossible,so redirect p directly to another branch.
				out := 1 ^ j
				child := parent.Succs[out].b
				if child == b {
					continue
				}
				b.removePred(k)
				p.Succs[pk.i] = Edge{child, len(child.Preds)}
				// Fix up Phi value in b to have one less argument.
				for _, v := range b.Values {
					if v.Op != OpPhi {
						continue
					}
					b.removePhiArg(v, k)
					phielimValue(v)
				}
				// Fix up child to have one more predecessor.
				child.Preds = append(child.Preds, Edge{p, pk.i})
				ai := b.Succs[out].i
				for _, v := range child.Values {
					if v.Op != OpPhi {
						continue
					}
					v.AddArg(v.Args[ai])
				}
				if b.Func.pass.debug > 0 {
					b.Func.Warnl(b.Controls[0].Pos, "Redirect %s based on %s", b.Controls[0].Op, p.Controls[0].Op)
				}
				changed = true
				k--
				break
			}
			ft.restore()
		}
		if len(b.Preds) == 0 && b != f.Entry {
			// Block is now dead.
			b.Kind = BlockInvalid
		}
	}
	ft.restore()
	ft.cleanup(f)
	return changed
}

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Editing: fuse_branchredirect.go

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