// clobber generates code to clobber pointer slots in all dead variables
// (those not marked in live). Clobbering instructions are added to the end
// of b.Values.
func clobber(lv *liveness, b *ssa.Block, live bitvec.BitVec) {
	for i, n := range lv.vars {
		if !live.Get(int32(i)) && !n.Addrtaken() && !n.OpenDeferSlot() && !n.IsOutputParamHeapAddr() {
			// Don't clobber stack objects (address-taken). They are
			// tracked dynamically.

	dst.Chmod(0500) // make executable

	// Clobber all the non-v1 opcodes.
	opcodes := map[string]bool{}
	var features []string
	for feature, opcodeList := range featureToOpcodes {
		if runtimeFeatures[feature] {
			features = append(features, fmt.Sprintf("cpu.%s=off", feature))
		}
		for _, op := range opcodeList {
			opcodes[op] = true
		}
	}
	clobber(t, os.Args[0], dst, opcodes)
	if err = dst.Close(); err != nil {

		v = leftShift(loadBlock, pos, v, shift0-(n-1)*size*8)
	}

	// Install with (Copy v).
	root.reset(OpCopy)
	root.AddArg(v)

	// Clobber the loads, just to prevent additional work being done on
	// subtrees (which are now unreachable).
	for i := int64(0); i < n; i++ {
		clobber(r[i].load)
	}
	return true
}

func memcombineStores(f *Func) {
	mark := f.newSparseSet(f.NumValues())
	defer f.retSparseSet(mark)

	load_g
	MOVD	g_racectx(g), R0	// goroutine context
	BL	racecall<>(SB)
	MOVD	R21, R9	// restore the original function
	// Call the atomic function.
	// racecall will call LLVM race code which might clobber R28 (g)
	load_g
	MOVD	g_racectx(g), R0	// goroutine context
	MOVD	16(RSP), R1	// caller pc
	MOVD	R9, R2	// pc
	ADD	$40, RSP, R3	// arguments
	BL	racecall<>(SB)
	// Call __tsan_go_ignore_sync_end.

	rootCmd.Flags().BoolVar(&globalArgs.NoCache, "no-cache", globalArgs.NoCache, "disable caching")
	rootCmd.Flags().BoolVar(&globalArgs.NoClobber, "no-clobber", globalArgs.NoClobber, "do not allow pushing images that already exist")
	rootCmd.Flags().StringVar(&globalArgs.Builder, "builder", globalArgs.Builder, "type of builder to use. options are crane or docker")

(MOVHreg  <t> x:(MOVHUload [off] {sym} ptr mem)) && x.Uses == 1 && clobber(x) => @x.Block (MOVHload  <t> [off] {sym} ptr mem)
(MOVWreg  <t> x:(MOVWUload [off] {sym} ptr mem)) && x.Uses == 1 && clobber(x) => @x.Block (MOVWload  <t> [off] {sym} ptr mem)

		cost := phi * 1
		if phi > 1 {
			// If we have more than 1 phi and some values in post have args
			// in yes or no blocks, we may have to recalculate condition, because
			// those args may clobber flags. For now assume that all operations clobber flags.
			cost += other * 1
		}
		return cost < maxcost
	}
}

// canSpeculativelyExecute reports whether every value in the block can

// to the buffer space in R8.
// It clobbers condition codes.
// It does not clobber any other general-purpose registers,
// but may clobber others (e.g., floating point registers).
// The act of CALLing gcWriteBarrier will clobber R14 (LR).
TEXT gcWriteBarrier<>(SB),NOSPLIT|NOFRAME,$0
	// Save the registers clobbered by the fast path.
	MOVM.DB.W	[R0,R1], (R13)
retry:
	MOVW	g_m(g), R0

// to the buffer space in R25.
// It clobbers R23 (the linker temp register).
// The act of CALLing gcWriteBarrier will clobber R31 (LR).
// It does not clobber any other general-purpose registers,
// but may clobber others (e.g., floating point registers).
TEXT gcWriteBarrier<>(SB),NOSPLIT,$192
	// Save the registers clobbered by the fast path.
	MOVV	R1, 184(R29)
	MOVV	R2, 192(R29)
retry:

// number of bytes of buffer needed in R9, and returns a pointer
// to the buffer space in R9.
// It clobbers R10 (the temp register) and R1 (used by PLT stub).
// It does not clobber any other general-purpose registers,
// but may clobber others (e.g., floating point registers).
TEXT gcWriteBarrier<>(SB),NOSPLIT,$96
	// Save the registers clobbered by the fast path.
	MOVD	R4, 96(R15)
retry:
	MOVD	g_m(g), R1
	MOVD	m_p(R1), R1