src/cmd/compile/internal/ssa/check.go - go - Git at Google

 // 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

 import (
 	"math"
 )

 // checkFunc checks invariants of f.
 func checkFunc(f *Func) {
 	blockMark := make([]bool, f.NumBlocks())
 	valueMark := make([]bool, f.NumValues())

 	for _, b := range f.Blocks {
 		if blockMark[b.ID] {
 			f.Fatalf("block %s appears twice in %s!", b, f.Name)
 		}
 		blockMark[b.ID] = true
 		if b.Func != f {
 			f.Fatalf("%s.Func=%s, want %s", b, b.Func.Name, f.Name)
 		}

 		for i, e := range b.Preds {
 			if se := e.b.Succs[e.i]; se.b != b || se.i != i {
 				f.Fatalf("block pred/succ not crosslinked correctly %d:%s %d:%s", i, b, se.i, se.b)
 			}
 		}
 		for i, e := range b.Succs {
 			if pe := e.b.Preds[e.i]; pe.b != b || pe.i != i {
 				f.Fatalf("block succ/pred not crosslinked correctly %d:%s %d:%s", i, b, pe.i, pe.b)
 			}
 		}

 		switch b.Kind {
 		case BlockExit:
 			if len(b.Succs) != 0 {
 				f.Fatalf("exit block %s has successors", b)
 			}
 			if b.Control == nil {
 				f.Fatalf("exit block %s has no control value", b)
 			}
 			if !b.Control.Type.IsMemory() {
 				f.Fatalf("exit block %s has non-memory control value %s", b, b.Control.LongString())
 			}
 		case BlockRet:
 			if len(b.Succs) != 0 {
 				f.Fatalf("ret block %s has successors", b)
 			}
 			if b.Control == nil {
 				f.Fatalf("ret block %s has nil control", b)
 			}
 			if !b.Control.Type.IsMemory() {
 				f.Fatalf("ret block %s has non-memory control value %s", b, b.Control.LongString())
 			}
 		case BlockRetJmp:
 			if len(b.Succs) != 0 {
 				f.Fatalf("retjmp block %s len(Succs)==%d, want 0", b, len(b.Succs))
 			}
 			if b.Control == nil {
 				f.Fatalf("retjmp block %s has nil control", b)
 			}
 			if !b.Control.Type.IsMemory() {
 				f.Fatalf("retjmp block %s has non-memory control value %s", b, b.Control.LongString())
 			}
 			if b.Aux == nil {
 				f.Fatalf("retjmp block %s has nil Aux field", b)
 			}
 		case BlockPlain:
 			if len(b.Succs) != 1 {
 				f.Fatalf("plain block %s len(Succs)==%d, want 1", b, len(b.Succs))
 			}
 			if b.Control != nil {
 				f.Fatalf("plain block %s has non-nil control %s", b, b.Control.LongString())
 			}
 		case BlockIf:
 			if len(b.Succs) != 2 {
 				f.Fatalf("if block %s len(Succs)==%d, want 2", b, len(b.Succs))
 			}
 			if b.Control == nil {
 				f.Fatalf("if block %s has no control value", b)
 			}
 			if !b.Control.Type.IsBoolean() {
 				f.Fatalf("if block %s has non-bool control value %s", b, b.Control.LongString())
 			}
 		case BlockDefer:
 			if len(b.Succs) != 2 {
 				f.Fatalf("defer block %s len(Succs)==%d, want 2", b, len(b.Succs))
 			}
 			if b.Control == nil {
 				f.Fatalf("defer block %s has no control value", b)
 			}
 			if !b.Control.Type.IsMemory() {
 				f.Fatalf("defer block %s has non-memory control value %s", b, b.Control.LongString())
 			}
 		case BlockFirst:
 			if len(b.Succs) != 2 {
 				f.Fatalf("plain/dead block %s len(Succs)==%d, want 2", b, len(b.Succs))
 			}
 			if b.Control != nil {
 				f.Fatalf("plain/dead block %s has a control value", b)
 			}
 		}
 		if len(b.Succs) != 2 && b.Likely != BranchUnknown {
 			f.Fatalf("likeliness prediction %d for block %s with %d successors", b.Likely, b, len(b.Succs))
 		}

 		for _, v := range b.Values {
 			// Check to make sure argument count makes sense (argLen of -1 indicates
 			// variable length args)
 			nArgs := opcodeTable[v.Op].argLen
 			if nArgs != -1 && int32(len(v.Args)) != nArgs {
 				f.Fatalf("value %s has %d args, expected %d", v.LongString(),
 					len(v.Args), nArgs)
 			}

 			// Check to make sure aux values make sense.
 			canHaveAux := false
 			canHaveAuxInt := false
 			switch opcodeTable[v.Op].auxType {
 			case auxNone:
 			case auxBool:
 				if v.AuxInt < 0 || v.AuxInt > 1 {
 					f.Fatalf("bad bool AuxInt value for %v", v)
 				}
 				canHaveAuxInt = true
 			case auxInt8:
 				if v.AuxInt != int64(int8(v.AuxInt)) {
 					f.Fatalf("bad int8 AuxInt value for %v", v)
 				}
 				canHaveAuxInt = true
 			case auxInt16:
 				if v.AuxInt != int64(int16(v.AuxInt)) {
 					f.Fatalf("bad int16 AuxInt value for %v", v)
 				}
 				canHaveAuxInt = true
 			case auxInt32:
 				if v.AuxInt != int64(int32(v.AuxInt)) {
 					f.Fatalf("bad int32 AuxInt value for %v", v)
 				}
 				canHaveAuxInt = true
 			case auxInt64, auxFloat64:
 				canHaveAuxInt = true
 			case auxInt128:
 				// AuxInt must be zero, so leave canHaveAuxInt set to false.
 			case auxFloat32:
 				canHaveAuxInt = true
 				if !isExactFloat32(v) {
 					f.Fatalf("value %v has an AuxInt value that is not an exact float32", v)
 				}
 			case auxString, auxSym, auxTyp:
 				canHaveAux = true
 			case auxSymOff, auxSymValAndOff, auxTypSize:
 				canHaveAuxInt = true
 				canHaveAux = true
 			case auxSymInt32:
 				if v.AuxInt != int64(int32(v.AuxInt)) {
 					f.Fatalf("bad int32 AuxInt value for %v", v)
 				}
 				canHaveAuxInt = true
 				canHaveAux = true
 			case auxCCop:
 				if _, ok := v.Aux.(Op); !ok {
 					f.Fatalf("bad type %T for CCop in %v", v.Aux, v)
 				}
 				canHaveAux = true
 			default:
 				f.Fatalf("unknown aux type for %s", v.Op)
 			}
 			if !canHaveAux && v.Aux != nil {
 				f.Fatalf("value %s has an Aux value %v but shouldn't", v.LongString(), v.Aux)
 			}
 			if !canHaveAuxInt && v.AuxInt != 0 {
 				f.Fatalf("value %s has an AuxInt value %d but shouldn't", v.LongString(), v.AuxInt)
 			}

 			for i, arg := range v.Args {
 				if arg == nil {
 					f.Fatalf("value %s has nil arg", v.LongString())
 				}
 				if v.Op != OpPhi {
 					// For non-Phi ops, memory args must be last, if present
 					if arg.Type.IsMemory() && i != len(v.Args)-1 {
 						f.Fatalf("value %s has non-final memory arg (%d < %d)", v.LongString(), i, len(v.Args)-1)
 					}
 				}
 			}

 			if valueMark[v.ID] {
 				f.Fatalf("value %s appears twice!", v.LongString())
 			}
 			valueMark[v.ID] = true

 			if v.Block != b {
 				f.Fatalf("%s.block != %s", v, b)
 			}
 			if v.Op == OpPhi && len(v.Args) != len(b.Preds) {
 				f.Fatalf("phi length %s does not match pred length %d for block %s", v.LongString(), len(b.Preds), b)
 			}

 			if v.Op == OpAddr {
 				if len(v.Args) == 0 {
 					f.Fatalf("no args for OpAddr %s", v.LongString())
 				}
 				if v.Args[0].Op != OpSP && v.Args[0].Op != OpSB {
 					f.Fatalf("bad arg to OpAddr %v", v)
 				}
 			}

 			if f.RegAlloc != nil && f.Config.SoftFloat && v.Type.IsFloat() {
 				f.Fatalf("unexpected floating-point type %v", v.LongString())
 			}

 			// Check types.
 			// TODO: more type checks?
 			switch c := f.Config; v.Op {
 			case OpSP, OpSB:
 				if v.Type != c.Types.Uintptr {
 					f.Fatalf("bad %s type: want uintptr, have %s",
 						v.Op, v.Type.String())
 				}
 			}

 			// TODO: check for cycles in values
 		}
 	}

 	// Check to make sure all Blocks referenced are in the function.
 	if !blockMark[f.Entry.ID] {
 		f.Fatalf("entry block %v is missing", f.Entry)
 	}
 	for _, b := range f.Blocks {
 		for _, c := range b.Preds {
 			if !blockMark[c.b.ID] {
 				f.Fatalf("predecessor block %v for %v is missing", c, b)
 			}
 		}
 		for _, c := range b.Succs {
 			if !blockMark[c.b.ID] {
 				f.Fatalf("successor block %v for %v is missing", c, b)
 			}
 		}
 	}

 	if len(f.Entry.Preds) > 0 {
 		f.Fatalf("entry block %s of %s has predecessor(s) %v", f.Entry, f.Name, f.Entry.Preds)
 	}

 	// Check to make sure all Values referenced are in the function.
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
 			for i, a := range v.Args {
 				if !valueMark[a.ID] {
 					f.Fatalf("%v, arg %d of %s, is missing", a, i, v.LongString())
 				}
 			}
 		}
 		if b.Control != nil && !valueMark[b.Control.ID] {
 			f.Fatalf("control value for %s is missing: %v", b, b.Control)
 		}
 	}
 	for b := f.freeBlocks; b != nil; b = b.succstorage[0].b {
 		if blockMark[b.ID] {
 			f.Fatalf("used block b%d in free list", b.ID)
 		}
 	}
 	for v := f.freeValues; v != nil; v = v.argstorage[0] {
 		if valueMark[v.ID] {
 			f.Fatalf("used value v%d in free list", v.ID)
 		}
 	}

 	// Check to make sure all args dominate uses.
 	if f.RegAlloc == nil {
 		// Note: regalloc introduces non-dominating args.
 		// See TODO in regalloc.go.
 		sdom := f.sdom()
 		for _, b := range f.Blocks {
 			for _, v := range b.Values {
 				for i, arg := range v.Args {
 					x := arg.Block
 					y := b
 					if v.Op == OpPhi {
 						y = b.Preds[i].b
 					}
 					if !domCheck(f, sdom, x, y) {
 						f.Fatalf("arg %d of value %s does not dominate, arg=%s", i, v.LongString(), arg.LongString())
 					}
 				}
 			}
 			if b.Control != nil && !domCheck(f, sdom, b.Control.Block, b) {
 				f.Fatalf("control value %s for %s doesn't dominate", b.Control, b)
 			}
 		}
 	}

 	// Check loop construction
 	if f.RegAlloc == nil && f.pass != nil { // non-nil pass allows better-targeted debug printing
 		ln := f.loopnest()
 		if !ln.hasIrreducible {
 			po := f.postorder() // use po to avoid unreachable blocks.
 			for _, b := range po {
 				for _, s := range b.Succs {
 					bb := s.Block()
 					if ln.b2l[b.ID] == nil && ln.b2l[bb.ID] != nil && bb != ln.b2l[bb.ID].header {
 						f.Fatalf("block %s not in loop branches to non-header block %s in loop", b.String(), bb.String())
 					}
 					if ln.b2l[b.ID] != nil && ln.b2l[bb.ID] != nil && bb != ln.b2l[bb.ID].header && !ln.b2l[b.ID].isWithinOrEq(ln.b2l[bb.ID]) {
 						f.Fatalf("block %s in loop branches to non-header block %s in non-containing loop", b.String(), bb.String())
 					}
 				}
 			}
 		}
 	}

 	// Check use counts
 	uses := make([]int32, f.NumValues())
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
 			for _, a := range v.Args {
 				uses[a.ID]++
 			}
 		}
 		if b.Control != nil {
 			uses[b.Control.ID]++
 		}
 	}
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
 			if v.Uses != uses[v.ID] {
 				f.Fatalf("%s has %d uses, but has Uses=%d", v, uses[v.ID], v.Uses)
 			}
 		}
 	}

 	memCheck(f)
 }

 func memCheck(f *Func) {
 	// Check that if a tuple has a memory type, it is second.
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
 			if v.Type.IsTuple() && v.Type.FieldType(0).IsMemory() {
 				f.Fatalf("memory is first in a tuple: %s\n", v.LongString())
 			}
 		}
 	}

 	// Single live memory checks.
 	// These checks only work if there are no memory copies.
 	// (Memory copies introduce ambiguity about which mem value is really live.
 	// probably fixable, but it's easier to avoid the problem.)
 	// For the same reason, disable this check if some memory ops are unused.
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
 			if (v.Op == OpCopy || v.Uses == 0) && v.Type.IsMemory() {
 				return
 			}
 		}
 		if b != f.Entry && len(b.Preds) == 0 {
 			return
 		}
 	}

 	// Compute live memory at the end of each block.
 	lastmem := make([]*Value, f.NumBlocks())
 	ss := newSparseSet(f.NumValues())
 	for _, b := range f.Blocks {
 		// Mark overwritten memory values. Those are args of other
 		// ops that generate memory values.
 		ss.clear()
 		for _, v := range b.Values {
 			if v.Op == OpPhi || !v.Type.IsMemory() {
 				continue
 			}
 			if m := v.MemoryArg(); m != nil {
 				ss.add(m.ID)
 			}
 		}
 		// There should be at most one remaining unoverwritten memory value.
 		for _, v := range b.Values {
 			if !v.Type.IsMemory() {
 				continue
 			}
 			if ss.contains(v.ID) {
 				continue
 			}
 			if lastmem[b.ID] != nil {
 				f.Fatalf("two live memory values in %s: %s and %s", b, lastmem[b.ID], v)
 			}
 			lastmem[b.ID] = v
 		}
 		// If there is no remaining memory value, that means there was no memory update.
 		// Take any memory arg.
 		if lastmem[b.ID] == nil {
 			for _, v := range b.Values {
 				if v.Op == OpPhi {
 					continue
 				}
 				m := v.MemoryArg()
 				if m == nil {
 					continue
 				}
 				if lastmem[b.ID] != nil && lastmem[b.ID] != m {
 					f.Fatalf("two live memory values in %s: %s and %s", b, lastmem[b.ID], m)
 				}
 				lastmem[b.ID] = m
 			}
 		}
 	}
 	// Propagate last live memory through storeless blocks.
 	for {
 		changed := false
 		for _, b := range f.Blocks {
 			if lastmem[b.ID] != nil {
 				continue
 			}
 			for _, e := range b.Preds {
 				p := e.b
 				if lastmem[p.ID] != nil {
 					lastmem[b.ID] = lastmem[p.ID]
 					changed = true
 					break
 				}
 			}
 		}
 		if !changed {
 			break
 		}
 	}
 	// Check merge points.
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
 			if v.Op == OpPhi && v.Type.IsMemory() {
 				for i, a := range v.Args {
 					if a != lastmem[b.Preds[i].b.ID] {
 						f.Fatalf("inconsistent memory phi %s %d %s %s", v.LongString(), i, a, lastmem[b.Preds[i].b.ID])
 					}
 				}
 			}
 		}
 	}

 	// Check that only one memory is live at any point.
 	if f.scheduled {
 		for _, b := range f.Blocks {
 			var mem *Value // the current live memory in the block
 			for _, v := range b.Values {
 				if v.Op == OpPhi {
 					if v.Type.IsMemory() {
 						mem = v
 					}
 					continue
 				}
 				if mem == nil && len(b.Preds) > 0 {
 					// If no mem phi, take mem of any predecessor.
 					mem = lastmem[b.Preds[0].b.ID]
 				}
 				for _, a := range v.Args {
 					if a.Type.IsMemory() && a != mem {
 						f.Fatalf("two live mems @ %s: %s and %s", v, mem, a)
 					}
 				}
 				if v.Type.IsMemory() {
 					mem = v
 				}
 			}
 		}
 	}

 	// Check that after scheduling, phis are always first in the block.
 	if f.scheduled {
 		for _, b := range f.Blocks {
 			seenNonPhi := false
 			for _, v := range b.Values {
 				switch v.Op {
 				case OpPhi:
 					if seenNonPhi {
 						f.Fatalf("phi after non-phi @ %s: %s", b, v)
 					}
 				default:
 					seenNonPhi = true
 				}
 			}
 		}
 	}
 }

 // domCheck reports whether x dominates y (including x==y).
 func domCheck(f *Func, sdom SparseTree, x, y *Block) bool {
 	if !sdom.isAncestorEq(f.Entry, y) {
 		// unreachable - ignore
 		return true
 	}
 	return sdom.isAncestorEq(x, y)
 }

 // isExactFloat32 reports whether v has an AuxInt that can be exactly represented as a float32.
 func isExactFloat32(v *Value) bool {
 	x := v.AuxFloat()
 	return math.Float64bits(x) == math.Float64bits(float64(float32(x)))
 }
	// 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

	import (
	"math"
	)

	// checkFunc checks invariants of f.
	func checkFunc(f *Func) {
	blockMark := make([]bool, f.NumBlocks())
	valueMark := make([]bool, f.NumValues())

	for _, b := range f.Blocks {
	if blockMark[b.ID] {
	f.Fatalf("block %s appears twice in %s!", b, f.Name)
	}
	blockMark[b.ID] = true
	if b.Func != f {
	f.Fatalf("%s.Func=%s, want %s", b, b.Func.Name, f.Name)
	}

	for i, e := range b.Preds {
	if se := e.b.Succs[e.i]; se.b != b \|\| se.i != i {
	f.Fatalf("block pred/succ not crosslinked correctly %d:%s %d:%s", i, b, se.i, se.b)
	}
	}
	for i, e := range b.Succs {
	if pe := e.b.Preds[e.i]; pe.b != b \|\| pe.i != i {
	f.Fatalf("block succ/pred not crosslinked correctly %d:%s %d:%s", i, b, pe.i, pe.b)
	}
	}

	switch b.Kind {
	case BlockExit:
	if len(b.Succs) != 0 {
	f.Fatalf("exit block %s has successors", b)
	}
	if b.Control == nil {
	f.Fatalf("exit block %s has no control value", b)
	}
	if !b.Control.Type.IsMemory() {
	f.Fatalf("exit block %s has non-memory control value %s", b, b.Control.LongString())
	}
	case BlockRet:
	if len(b.Succs) != 0 {
	f.Fatalf("ret block %s has successors", b)
	}
	if b.Control == nil {
	f.Fatalf("ret block %s has nil control", b)
	}
	if !b.Control.Type.IsMemory() {
	f.Fatalf("ret block %s has non-memory control value %s", b, b.Control.LongString())
	}
	case BlockRetJmp:
	if len(b.Succs) != 0 {
	f.Fatalf("retjmp block %s len(Succs)==%d, want 0", b, len(b.Succs))
	}
	if b.Control == nil {
	f.Fatalf("retjmp block %s has nil control", b)
	}
	if !b.Control.Type.IsMemory() {
	f.Fatalf("retjmp block %s has non-memory control value %s", b, b.Control.LongString())
	}
	if b.Aux == nil {
	f.Fatalf("retjmp block %s has nil Aux field", b)
	}
	case BlockPlain:
	if len(b.Succs) != 1 {
	f.Fatalf("plain block %s len(Succs)==%d, want 1", b, len(b.Succs))
	}
	if b.Control != nil {
	f.Fatalf("plain block %s has non-nil control %s", b, b.Control.LongString())
	}
	case BlockIf:
	if len(b.Succs) != 2 {
	f.Fatalf("if block %s len(Succs)==%d, want 2", b, len(b.Succs))
	}
	if b.Control == nil {
	f.Fatalf("if block %s has no control value", b)
	}
	if !b.Control.Type.IsBoolean() {
	f.Fatalf("if block %s has non-bool control value %s", b, b.Control.LongString())
	}
	case BlockDefer:
	if len(b.Succs) != 2 {
	f.Fatalf("defer block %s len(Succs)==%d, want 2", b, len(b.Succs))
	}
	if b.Control == nil {
	f.Fatalf("defer block %s has no control value", b)
	}
	if !b.Control.Type.IsMemory() {
	f.Fatalf("defer block %s has non-memory control value %s", b, b.Control.LongString())
	}
	case BlockFirst:
	if len(b.Succs) != 2 {
	f.Fatalf("plain/dead block %s len(Succs)==%d, want 2", b, len(b.Succs))
	}
	if b.Control != nil {
	f.Fatalf("plain/dead block %s has a control value", b)
	}
	}
	if len(b.Succs) != 2 && b.Likely != BranchUnknown {
	f.Fatalf("likeliness prediction %d for block %s with %d successors", b.Likely, b, len(b.Succs))
	}

	for _, v := range b.Values {
	// Check to make sure argument count makes sense (argLen of -1 indicates
	// variable length args)
	nArgs := opcodeTable[v.Op].argLen
	if nArgs != -1 && int32(len(v.Args)) != nArgs {
	f.Fatalf("value %s has %d args, expected %d", v.LongString(),
	len(v.Args), nArgs)
	}

	// Check to make sure aux values make sense.
	canHaveAux := false
	canHaveAuxInt := false
	switch opcodeTable[v.Op].auxType {
	case auxNone:
	case auxBool:
	if v.AuxInt < 0 \|\| v.AuxInt > 1 {
	f.Fatalf("bad bool AuxInt value for %v", v)
	}
	canHaveAuxInt = true
	case auxInt8:
	if v.AuxInt != int64(int8(v.AuxInt)) {
	f.Fatalf("bad int8 AuxInt value for %v", v)
	}
	canHaveAuxInt = true
	case auxInt16:
	if v.AuxInt != int64(int16(v.AuxInt)) {
	f.Fatalf("bad int16 AuxInt value for %v", v)
	}
	canHaveAuxInt = true
	case auxInt32:
	if v.AuxInt != int64(int32(v.AuxInt)) {
	f.Fatalf("bad int32 AuxInt value for %v", v)
	}
	canHaveAuxInt = true
	case auxInt64, auxFloat64:
	canHaveAuxInt = true
	case auxInt128:
	// AuxInt must be zero, so leave canHaveAuxInt set to false.
	case auxFloat32:
	canHaveAuxInt = true
	if !isExactFloat32(v) {
	f.Fatalf("value %v has an AuxInt value that is not an exact float32", v)
	}
	case auxString, auxSym, auxTyp:
	canHaveAux = true
	case auxSymOff, auxSymValAndOff, auxTypSize:
	canHaveAuxInt = true
	canHaveAux = true
	case auxSymInt32:
	if v.AuxInt != int64(int32(v.AuxInt)) {
	f.Fatalf("bad int32 AuxInt value for %v", v)
	}
	canHaveAuxInt = true
	canHaveAux = true
	case auxCCop:
	if _, ok := v.Aux.(Op); !ok {
	f.Fatalf("bad type %T for CCop in %v", v.Aux, v)
	}
	canHaveAux = true
	default:
	f.Fatalf("unknown aux type for %s", v.Op)
	}
	if !canHaveAux && v.Aux != nil {
	f.Fatalf("value %s has an Aux value %v but shouldn't", v.LongString(), v.Aux)
	}
	if !canHaveAuxInt && v.AuxInt != 0 {
	f.Fatalf("value %s has an AuxInt value %d but shouldn't", v.LongString(), v.AuxInt)
	}

	for i, arg := range v.Args {
	if arg == nil {
	f.Fatalf("value %s has nil arg", v.LongString())
	}
	if v.Op != OpPhi {
	// For non-Phi ops, memory args must be last, if present
	if arg.Type.IsMemory() && i != len(v.Args)-1 {
	f.Fatalf("value %s has non-final memory arg (%d < %d)", v.LongString(), i, len(v.Args)-1)
	}
	}
	}

	if valueMark[v.ID] {
	f.Fatalf("value %s appears twice!", v.LongString())
	}
	valueMark[v.ID] = true

	if v.Block != b {
	f.Fatalf("%s.block != %s", v, b)
	}
	if v.Op == OpPhi && len(v.Args) != len(b.Preds) {
	f.Fatalf("phi length %s does not match pred length %d for block %s", v.LongString(), len(b.Preds), b)
	}

	if v.Op == OpAddr {
	if len(v.Args) == 0 {
	f.Fatalf("no args for OpAddr %s", v.LongString())
	}
	if v.Args[0].Op != OpSP && v.Args[0].Op != OpSB {
	f.Fatalf("bad arg to OpAddr %v", v)
	}
	}

	if f.RegAlloc != nil && f.Config.SoftFloat && v.Type.IsFloat() {
	f.Fatalf("unexpected floating-point type %v", v.LongString())
	}

	// Check types.
	// TODO: more type checks?
	switch c := f.Config; v.Op {
	case OpSP, OpSB:
	if v.Type != c.Types.Uintptr {
	f.Fatalf("bad %s type: want uintptr, have %s",
	v.Op, v.Type.String())
	}
	}

	// TODO: check for cycles in values
	}
	}

	// Check to make sure all Blocks referenced are in the function.
	if !blockMark[f.Entry.ID] {
	f.Fatalf("entry block %v is missing", f.Entry)
	}
	for _, b := range f.Blocks {
	for _, c := range b.Preds {
	if !blockMark[c.b.ID] {
	f.Fatalf("predecessor block %v for %v is missing", c, b)
	}
	}
	for _, c := range b.Succs {
	if !blockMark[c.b.ID] {
	f.Fatalf("successor block %v for %v is missing", c, b)
	}
	}
	}

	if len(f.Entry.Preds) > 0 {
	f.Fatalf("entry block %s of %s has predecessor(s) %v", f.Entry, f.Name, f.Entry.Preds)
	}

	// Check to make sure all Values referenced are in the function.
	for _, b := range f.Blocks {
	for _, v := range b.Values {
	for i, a := range v.Args {
	if !valueMark[a.ID] {
	f.Fatalf("%v, arg %d of %s, is missing", a, i, v.LongString())
	}
	}
	}
	if b.Control != nil && !valueMark[b.Control.ID] {
	f.Fatalf("control value for %s is missing: %v", b, b.Control)
	}
	}
	for b := f.freeBlocks; b != nil; b = b.succstorage[0].b {
	if blockMark[b.ID] {
	f.Fatalf("used block b%d in free list", b.ID)
	}
	}
	for v := f.freeValues; v != nil; v = v.argstorage[0] {
	if valueMark[v.ID] {
	f.Fatalf("used value v%d in free list", v.ID)
	}
	}

	// Check to make sure all args dominate uses.
	if f.RegAlloc == nil {
	// Note: regalloc introduces non-dominating args.
	// See TODO in regalloc.go.
	sdom := f.sdom()
	for _, b := range f.Blocks {
	for _, v := range b.Values {
	for i, arg := range v.Args {
	x := arg.Block
	y := b
	if v.Op == OpPhi {
	y = b.Preds[i].b
	}
	if !domCheck(f, sdom, x, y) {
	f.Fatalf("arg %d of value %s does not dominate, arg=%s", i, v.LongString(), arg.LongString())
	}
	}
	}
	if b.Control != nil && !domCheck(f, sdom, b.Control.Block, b) {
	f.Fatalf("control value %s for %s doesn't dominate", b.Control, b)
	}
	}
	}

	// Check loop construction
	if f.RegAlloc == nil && f.pass != nil { // non-nil pass allows better-targeted debug printing
	ln := f.loopnest()
	if !ln.hasIrreducible {
	po := f.postorder() // use po to avoid unreachable blocks.
	for _, b := range po {
	for _, s := range b.Succs {
	bb := s.Block()
	if ln.b2l[b.ID] == nil && ln.b2l[bb.ID] != nil && bb != ln.b2l[bb.ID].header {
	f.Fatalf("block %s not in loop branches to non-header block %s in loop", b.String(), bb.String())
	}
	if ln.b2l[b.ID] != nil && ln.b2l[bb.ID] != nil && bb != ln.b2l[bb.ID].header && !ln.b2l[b.ID].isWithinOrEq(ln.b2l[bb.ID]) {
	f.Fatalf("block %s in loop branches to non-header block %s in non-containing loop", b.String(), bb.String())
	}
	}
	}
	}
	}

	// Check use counts
	uses := make([]int32, f.NumValues())
	for _, b := range f.Blocks {
	for _, v := range b.Values {
	for _, a := range v.Args {
	uses[a.ID]++
	}
	}
	if b.Control != nil {
	uses[b.Control.ID]++
	}
	}
	for _, b := range f.Blocks {
	for _, v := range b.Values {
	if v.Uses != uses[v.ID] {
	f.Fatalf("%s has %d uses, but has Uses=%d", v, uses[v.ID], v.Uses)
	}
	}
	}

	memCheck(f)
	}

	func memCheck(f *Func) {
	// Check that if a tuple has a memory type, it is second.
	for _, b := range f.Blocks {
	for _, v := range b.Values {
	if v.Type.IsTuple() && v.Type.FieldType(0).IsMemory() {
	f.Fatalf("memory is first in a tuple: %s\n", v.LongString())
	}
	}
	}

	// Single live memory checks.
	// These checks only work if there are no memory copies.
	// (Memory copies introduce ambiguity about which mem value is really live.
	// probably fixable, but it's easier to avoid the problem.)
	// For the same reason, disable this check if some memory ops are unused.
	for _, b := range f.Blocks {
	for _, v := range b.Values {
	if (v.Op == OpCopy \|\| v.Uses == 0) && v.Type.IsMemory() {
	return
	}
	}
	if b != f.Entry && len(b.Preds) == 0 {
	return
	}
	}

	// Compute live memory at the end of each block.
	lastmem := make([]*Value, f.NumBlocks())
	ss := newSparseSet(f.NumValues())
	for _, b := range f.Blocks {
	// Mark overwritten memory values. Those are args of other
	// ops that generate memory values.
	ss.clear()
	for _, v := range b.Values {
	if v.Op == OpPhi \|\| !v.Type.IsMemory() {
	continue
	}
	if m := v.MemoryArg(); m != nil {
	ss.add(m.ID)
	}
	}
	// There should be at most one remaining unoverwritten memory value.
	for _, v := range b.Values {
	if !v.Type.IsMemory() {
	continue
	}
	if ss.contains(v.ID) {
	continue
	}
	if lastmem[b.ID] != nil {
	f.Fatalf("two live memory values in %s: %s and %s", b, lastmem[b.ID], v)
	}
	lastmem[b.ID] = v
	}
	// If there is no remaining memory value, that means there was no memory update.
	// Take any memory arg.
	if lastmem[b.ID] == nil {
	for _, v := range b.Values {
	if v.Op == OpPhi {
	continue
	}
	m := v.MemoryArg()
	if m == nil {
	continue
	}
	if lastmem[b.ID] != nil && lastmem[b.ID] != m {
	f.Fatalf("two live memory values in %s: %s and %s", b, lastmem[b.ID], m)
	}
	lastmem[b.ID] = m
	}
	}
	}
	// Propagate last live memory through storeless blocks.
	for {
	changed := false
	for _, b := range f.Blocks {
	if lastmem[b.ID] != nil {
	continue
	}
	for _, e := range b.Preds {
	p := e.b
	if lastmem[p.ID] != nil {
	lastmem[b.ID] = lastmem[p.ID]
	changed = true
	break
	}
	}
	}
	if !changed {
	break
	}
	}
	// Check merge points.
	for _, b := range f.Blocks {
	for _, v := range b.Values {
	if v.Op == OpPhi && v.Type.IsMemory() {
	for i, a := range v.Args {
	if a != lastmem[b.Preds[i].b.ID] {
	f.Fatalf("inconsistent memory phi %s %d %s %s", v.LongString(), i, a, lastmem[b.Preds[i].b.ID])
	}
	}
	}
	}
	}

	// Check that only one memory is live at any point.
	if f.scheduled {
	for _, b := range f.Blocks {
	var mem *Value // the current live memory in the block
	for _, v := range b.Values {
	if v.Op == OpPhi {
	if v.Type.IsMemory() {
	mem = v
	}
	continue
	}
	if mem == nil && len(b.Preds) > 0 {
	// If no mem phi, take mem of any predecessor.
	mem = lastmem[b.Preds[0].b.ID]
	}
	for _, a := range v.Args {
	if a.Type.IsMemory() && a != mem {
	f.Fatalf("two live mems @ %s: %s and %s", v, mem, a)
	}
	}
	if v.Type.IsMemory() {
	mem = v
	}
	}
	}
	}

	// Check that after scheduling, phis are always first in the block.
	if f.scheduled {
	for _, b := range f.Blocks {
	seenNonPhi := false
	for _, v := range b.Values {
	switch v.Op {
	case OpPhi:
	if seenNonPhi {
	f.Fatalf("phi after non-phi @ %s: %s", b, v)
	}
	default:
	seenNonPhi = true
	}
	}
	}
	}
	}

	// domCheck reports whether x dominates y (including x==y).
	func domCheck(f Func, sdom SparseTree, x, y Block) bool {
	if !sdom.isAncestorEq(f.Entry, y) {
	// unreachable - ignore
	return true
	}
	return sdom.isAncestorEq(x, y)
	}

	// isExactFloat32 reports whether v has an AuxInt that can be exactly represented as a float32.
	func isExactFloat32(v *Value) bool {
	x := v.AuxFloat()
	return math.Float64bits(x) == math.Float64bits(float64(float32(x)))
	}