// license that can be found in the LICENSE file.

package ssa

import (
	"cmd/internal/src"
	"fmt"
	"sort"
)

func isPoorStatementOp(op Op) bool {
	switch op {
	// Note that Nilcheck often vanishes, but when it doesn't, you'd love to start the statement there
	// so that a debugger-user sees the stop before the panic, and can examine the value.

// It requires a postorder numbering of all the blocks.
func intersect(b, c *Block, postnum []int, idom []*Block) *Block {
	// TODO: This loop is O(n^2). It used to be used in nilcheck,
	// see BenchmarkNilCheckDeep*.
	for b != c {
		if postnum[b.ID] < postnum[c.ID] {
			b = idom[b.ID]
		} else {
			c = idom[c.ID]
		}
	}
	return b

// There may be false positives.
func isEmpty(b *Block) bool {
	for _, v := range b.Values {
		if v.Uses > 0 || v.Op.IsCall() || v.Op.HasSideEffects() || v.Type.IsVoid() || opcodeTable[v.Op].nilCheck {
			return false
		}
	}
	return true
}

// fuseBlockPlain handles a run of blocks with length >= 2,
// whose interior has single predecessors and successors,

						} // TODO and if this fails?
					}
					v.SetArg(i, x)
					rewrites++
				}
			}
		}
		for i, v := range b.ControlValues() {
			if x := rewrite[v.ID]; x != nil {
				if v.Op == OpNilCheck {
					// nilcheck pass will remove the nil checks and log
					// them appropriately, so don't mess with them here.
					continue
				}
				b.ReplaceControl(i, x)
			}
		}
	}

	if f.pass.stats > 0 {

					liveOrderStmts = append(liveOrderStmts, v)
				}
			}
		}
		for _, v := range b.Values {
			if (opcodeTable[v.Op].call || opcodeTable[v.Op].hasSideEffects || opcodeTable[v.Op].nilCheck) && !live[v.ID] {
				live[v.ID] = true
				q = append(q, v)
				if v.Pos.IsStmt() != src.PosNotStmt {
					liveOrderStmts = append(liveOrderStmts, v)
				}
			}
			if v.Op == OpInlMark {

		{name: "LoweredNilCheck", argLength: 2, reg: regInfo{inputs: []regMask{gp}}, nilCheck: true, faultOnNilArg0: true}, // panic if arg0 is nil. arg1=mem

(TailCall ...) => (LoweredTailCall ...)

// Miscellaneous
(Convert ...) => (LoweredConvert ...)
(IsNonNil p) => (I64Eqz (I64Eqz p))
(IsInBounds ...) => (I64LtU ...)
(IsSliceInBounds ...) => (I64LeU ...)
(NilCheck ...) => (LoweredNilCheck ...)
(GetClosurePtr ...) => (LoweredGetClosurePtr ...)
(GetCallerPC ...) => (LoweredGetCallerPC ...)
(GetCallerSP ...) => (LoweredGetCallerSP ...)
(Addr {sym} base) => (LoweredAddr {sym} [0] base)

// if its use count drops to 0.
func (v *Value) removeable() bool {
	if v.Type.IsVoid() {
		// Void ops (inline marks), must stay.
		return false
	}
	if opcodeTable[v.Op].nilCheck {
		// Nil pointer checks must stay.
		return false
	}
	if v.Type.IsMemory() {
		// We don't need to preserve all memory ops, but we do need
		// to keep calls at least (because they might have

	needIntTemp       bool      // need a temporary free integer register
	call              bool      // is a function call
	tailCall          bool      // is a tail call
	nilCheck          bool      // this op is a nil check on arg0
	faultOnNilArg0    bool      // this op will fault if arg0 is nil (and aux encodes a small offset)

		s.Prog(wasm.AIf)
		p := s.Prog(wasm.ACALLNORESUME)
		p.To = obj.Addr{Type: obj.TYPE_MEM, Name: obj.NAME_EXTERN, Sym: ir.Syms.SigPanic}
		s.Prog(wasm.AEnd)
		if logopt.Enabled() {
			logopt.LogOpt(v.Pos, "nilcheck", "genssa", v.Block.Func.Name)
		}
		if base.Debug.Nil != 0 && v.Pos.Line() > 1 { // v.Pos.Line()==1 in generated wrappers
			base.WarnfAt(v.Pos, "generated nil check")
		}

	case ssa.OpWasmLoweredWB: