Gecko [ 167.86.127.34 ]

Name	Size	Permission
gen	[ DIR ]	drwxr-xr-x
testdata	[ DIR ]	drwxr-xr-x
README.md	7.76 KB	-rw-r--r--
TODO	950 B	-rw-r--r--
biasedsparsemap.go	2.71 KB	-rw-r--r--
block.go	8.64 KB	-rw-r--r--
branchelim.go	11.41 KB	-rw-r--r--
branchelim_test.go	5.21 KB	-rw-r--r--
cache.go	2.46 KB	-rw-r--r--
check.go	13.9 KB	-rw-r--r--
checkbce.go	956 B	-rw-r--r--
compile.go	16.22 KB	-rw-r--r--
config.go	11.39 KB	-rw-r--r--
copyelim.go	1.82 KB	-rw-r--r--
copyelim_test.go	1.29 KB	-rw-r--r--
critical.go	3.15 KB	-rw-r--r--
cse.go	10.62 KB	-rw-r--r--
cse_test.go	4.21 KB	-rw-r--r--
deadcode.go	9.73 KB	-rw-r--r--
deadcode_test.go	3.49 KB	-rw-r--r--
deadstore.go	8.98 KB	-rw-r--r--
deadstore_test.go	4.09 KB	-rw-r--r--
debug.go	33.92 KB	-rw-r--r--
debug_test.go	28.68 KB	-rw-r--r--
decompose.go	10.91 KB	-rw-r--r--
dom.go	7.98 KB	-rw-r--r--
dom_test.go	13.34 KB	-rw-r--r--
export_test.go	5.68 KB	-rw-r--r--
flagalloc.go	5.49 KB	-rw-r--r--
func.go	22.17 KB	-rw-r--r--
func_test.go	12.85 KB	-rw-r--r--
fuse.go	5.7 KB	-rw-r--r--
fuse_test.go	5.04 KB	-rw-r--r--
html.go	29.04 KB	-rw-r--r--
id.go	576 B	-rw-r--r--
layout.go	3.56 KB	-rw-r--r--
lca.go	3.71 KB	-rw-r--r--
lca_test.go	1.65 KB	-rw-r--r--
likelyadjust.go	15.23 KB	-rw-r--r--
location.go	2.8 KB	-rw-r--r--
loopbce.go	9.85 KB	-rw-r--r--
loopreschedchecks.go	15.36 KB	-rw-r--r--
looprotate.go	2.24 KB	-rw-r--r--
lower.go	1.24 KB	-rw-r--r--
magic.go	13.42 KB	-rw-r--r--
magic_test.go	9.1 KB	-rw-r--r--
nilcheck.go	11.11 KB	-rw-r--r--
nilcheck_test.go	12.07 KB	-rw-r--r--
numberlines.go	8.44 KB	-rw-r--r--
op.go	8.74 KB	-rw-r--r--
opGen.go	839.32 KB	-rw-r--r--
opt.go	290 B	-rw-r--r--
passbm_test.go	3.14 KB	-rw-r--r--
phielim.go	1.47 KB	-rw-r--r--
phiopt.go	3.96 KB	-rw-r--r--
poset.go	37.23 KB	-rw-r--r--
poset_test.go	18.14 KB	-rw-r--r--
print.go	2.98 KB	-rw-r--r--
prove.go	36.68 KB	-rw-r--r--
redblack32.go	8.9 KB	-rw-r--r--
redblack32_test.go	5.96 KB	-rw-r--r--
regalloc.go	76.36 KB	-rw-r--r--
regalloc_test.go	6.41 KB	-rw-r--r--
rewrite.go	33.06 KB	-rw-r--r--
rewrite386.go	514.14 KB	-rw-r--r--
rewrite386splitload.go	3.7 KB	-rw-r--r--
rewriteAMD64.go	1.31 MB	-rw-r--r--
rewriteAMD64splitload.go	4.95 KB	-rw-r--r--
rewriteARM.go	538.26 KB	-rw-r--r--
rewriteARM64.go	837.68 KB	-rw-r--r--
rewriteMIPS.go	203.31 KB	-rw-r--r--
rewriteMIPS64.go	227.84 KB	-rw-r--r--
rewritePPC64.go	661.88 KB	-rw-r--r--
rewriteRISCV64.go	123.11 KB	-rw-r--r--
rewriteS390X.go	904.36 KB	-rw-r--r--
rewriteWasm.go	136.86 KB	-rw-r--r--
rewrite_test.go	3.01 KB	-rw-r--r--
rewritedec.go	10.56 KB	-rw-r--r--
rewritedec64.go	64.01 KB	-rw-r--r--
rewritedecArgs.go	6.6 KB	-rw-r--r--
rewritegeneric.go	1.09 MB	-rw-r--r--
schedule.go	13.99 KB	-rw-r--r--
schedule_test.go	2.91 KB	-rw-r--r--
shift_test.go	4.05 KB	-rw-r--r--
shortcircuit.go	3.97 KB	-rw-r--r--
shortcircuit_test.go	1.31 KB	-rw-r--r--
sizeof_test.go	855 B	-rw-r--r--
softfloat.go	1.94 KB	-rw-r--r--
sparsemap.go	1.98 KB	-rw-r--r--
sparseset.go	1.54 KB	-rw-r--r--
sparsetree.go	7.88 KB	-rw-r--r--
sparsetreemap.go	7.67 KB	-rw-r--r--
stackalloc.go	10.95 KB	-rw-r--r--
stackframe.go	290 B	-rw-r--r--
stmtlines_test.go	2.75 KB	-rw-r--r--
tighten.go	4.21 KB	-rw-r--r--
trim.go	4.24 KB	-rw-r--r--
value.go	10.71 KB	-rw-r--r--
writebarrier.go	17.92 KB	-rw-r--r--
writebarrier_test.go	1.75 KB	-rw-r--r--
xposmap.go	3.29 KB	-rw-r--r--
zcse.go	2.12 KB	-rw-r--r--
zeroextension_test.go	1.66 KB	-rw-r--r--

Code Editor : flagalloc.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

// flagalloc allocates the flag register among all the flag-generating
// instructions. Flag values are recomputed if they need to be
// spilled/restored.
func flagalloc(f *Func) {
	// Compute the in-register flag value we want at the end of
	// each block. This is basically a best-effort live variable
	// analysis, so it can be much simpler than a full analysis.
	end := make([]*Value, f.NumBlocks())
	po := f.postorder()
	for n := 0; n < 2; n++ {
		for _, b := range po {
			// Walk values backwards to figure out what flag
			// value we want in the flag register at the start
			// of the block.
			var flag *Value
			for _, c := range b.ControlValues() {
				if c.Type.IsFlags() {
					if flag != nil {
						panic("cannot have multiple controls using flags")
					}
					flag = c
				}
			}
			if flag == nil {
				flag = end[b.ID]
			}
			for j := len(b.Values) - 1; j >= 0; j-- {
				v := b.Values[j]
				if v == flag {
					flag = nil
				}
				if v.clobbersFlags() {
					flag = nil
				}
				for _, a := range v.Args {
					if a.Type.IsFlags() {
						flag = a
					}
				}
			}
			if flag != nil {
				for _, e := range b.Preds {
					p := e.b
					end[p.ID] = flag
				}
			}
		}
	}

// For blocks which have a flags control value, that's the only value
	// we can leave in the flags register at the end of the block. (There
	// is no place to put a flag regeneration instruction.)
	for _, b := range f.Blocks {
		if b.Kind == BlockDefer {
			// Defer blocks internally use/clobber the flags value.
			end[b.ID] = nil
			continue
		}
		for _, v := range b.ControlValues() {
			if v.Type.IsFlags() && end[b.ID] != v {
				end[b.ID] = nil
			}
		}
	}

// Compute which flags values will need to be spilled.
	spill := map[ID]bool{}
	for _, b := range f.Blocks {
		var flag *Value
		if len(b.Preds) > 0 {
			flag = end[b.Preds[0].b.ID]
		}
		for _, v := range b.Values {
			for _, a := range v.Args {
				if !a.Type.IsFlags() {
					continue
				}
				if a == flag {
					continue
				}
				// a will need to be restored here.
				spill[a.ID] = true
				flag = a
			}
			if v.clobbersFlags() {
				flag = nil
			}
			if v.Type.IsFlags() {
				flag = v
			}
		}
		for _, v := range b.ControlValues() {
			if v != flag && v.Type.IsFlags() {
				spill[v.ID] = true
			}
		}
		if v := end[b.ID]; v != nil && v != flag {
			spill[v.ID] = true
		}
	}

// Add flag spill and recomputation where they are needed.
	// TODO: Remove original instructions if they are never used.
	var oldSched []*Value
	for _, b := range f.Blocks {
		oldSched = append(oldSched[:0], b.Values...)
		b.Values = b.Values[:0]
		// The current live flag value (the pre-flagalloc copy).
		var flag *Value
		if len(b.Preds) > 0 {
			flag = end[b.Preds[0].b.ID]
			// Note: the following condition depends on the lack of critical edges.
			for _, e := range b.Preds[1:] {
				p := e.b
				if end[p.ID] != flag {
					f.Fatalf("live flag in %s's predecessors not consistent", b)
				}
			}
		}
		for _, v := range oldSched {
			if v.Op == OpPhi && v.Type.IsFlags() {
				f.Fatalf("phi of flags not supported: %s", v.LongString())
			}

// If v will be spilled, and v uses memory, then we must split it
			// into a load + a flag generator.
			if spill[v.ID] && v.MemoryArg() != nil {
				if !f.Config.splitLoad(v) {
					f.Fatalf("can't split flag generator: %s", v.LongString())
				}
			}

// Make sure any flag arg of v is in the flags register.
			// If not, recompute it.
			for i, a := range v.Args {
				if !a.Type.IsFlags() {
					continue
				}
				if a == flag {
					continue
				}
				// Recalculate a
				c := copyFlags(a, b)
				// Update v.
				v.SetArg(i, c)
				// Remember the most-recently computed flag value.
				flag = a
			}
			// Issue v.
			b.Values = append(b.Values, v)
			if v.clobbersFlags() {
				flag = nil
			}
			if v.Type.IsFlags() {
				flag = v
			}
		}
		for i, v := range b.ControlValues() {
			if v != flag && v.Type.IsFlags() {
				// Recalculate control value.
				c := copyFlags(v, b)
				b.ReplaceControl(i, c)
				flag = v
			}
		}
		if v := end[b.ID]; v != nil && v != flag {
			// Need to reissue flag generator for use by
			// subsequent blocks.
			copyFlags(v, b)
			// Note: this flag generator is not properly linked up
			// with the flag users. This breaks the SSA representation.
			// We could fix up the users with another pass, but for now
			// we'll just leave it.  (Regalloc has the same issue for
			// standard regs, and it runs next.)
		}
	}

// Save live flag state for later.
	for _, b := range f.Blocks {
		b.FlagsLiveAtEnd = end[b.ID] != nil
	}
}

func (v *Value) clobbersFlags() bool {
	if opcodeTable[v.Op].clobberFlags {
		return true
	}
	if v.Type.IsTuple() && (v.Type.FieldType(0).IsFlags() || v.Type.FieldType(1).IsFlags()) {
		// This case handles the possibility where a flag value is generated but never used.
		// In that case, there's no corresponding Select to overwrite the flags value,
		// so we must consider flags clobbered by the tuple-generating instruction.
		return true
	}
	return false
}

// copyFlags copies v (flag generator) into b, returns the copy.
// If v's arg is also flags, copy recursively.
func copyFlags(v *Value, b *Block) *Value {
	flagsArgs := make(map[int]*Value)
	for i, a := range v.Args {
		if a.Type.IsFlags() || a.Type.IsTuple() {
			flagsArgs[i] = copyFlags(a, b)
		}
	}
	c := v.copyInto(b)
	for i, a := range flagsArgs {
		c.SetArg(i, a)
	}
	return c
}

${this.title}

Code Editor : flagalloc.go