// not Linux decides to back this memory with transparent huge
	// pages. There's latency involved in this zeroing, but the hugepage
	// gains are almost always worth it. Note: it's important that we
	// clear even if it's freshly mapped and we know there's no point
	// to zeroing as *that* is the critical signal to use huge pages.
	memclrNoHeapPointers(unsafe.Pointer(s.base()), s.elemsize)
	s.needzero = 0

// already zeroed. Otherwise if needzero is true, objects are zeroed as
// they are allocated. There are various benefits to delaying zeroing
// this way:
//
//	1. Stack frame allocation can avoid zeroing altogether.
//
//	2. It exhibits better temporal locality, since the program is
//	   probably about to write to the memory.
//
//	3. We don't zero pages that never get reused.

	b.Kind = kind
	b.ResetControls()
	b.Aux = nil
	b.AuxInt = 0
	b.Controls[0] = v
	b.Controls[1] = w
	v.Uses++
	w.Uses++
}

// truncateValues truncates b.Values at the ith element, zeroing subsequent elements.
// The values in b.Values after i must already have had their args reset,
// to maintain correct value uses counts.
func (b *Block) truncateValues(i int) {
	tail := b.Values[i:]

             * corresponds to the least significant nonzero byte in lw ^ rw, since lw and rw are
             * little-endian. Long.numberOfTrailingZeros(diff) tells us the least significant
             * nonzero bit, and zeroing out the first three bits of L.nTZ gives us the shift to get
             * that least significant nonzero byte.
             */
            int n = Long.numberOfTrailingZeros(lw ^ rw) & ~0x7;

             * corresponds to the least significant nonzero byte in lw ^ rw, since lw and rw are
             * little-endian. Long.numberOfTrailingZeros(diff) tells us the least significant
             * nonzero bit, and zeroing out the first three bits of L.nTZ gives us the shift to get
             * that least significant nonzero byte.
             */
            int n = Long.numberOfTrailingZeros(lw ^ rw) & ~0x7;

			},
			typ:            "Mem",
			faultOnNilArg0: true,
			faultOnNilArg1: true,
		},

		// Generic moves and zeros

		// general unaligned zeroing
		// arg0 = address of memory to zero (in X5, changed as side effect)
		// arg1 = address of the last element to zero (inclusive)
		// arg2 = mem
		// auxint = element size
		// returns mem
		//	mov	ZERO, (X5)

// strip off fractional word zeroing
(Zero [s] ptr mem) && s%16 != 0 && s%16 <= 8 && s > 16 =>
	(Zero [8]
		(OffPtr <ptr.Type> ptr [s-8])
		(Zero [s-s%16] ptr mem))
(Zero [s] ptr mem) && s%16 != 0 && s%16 > 8 && s > 16 =>
	(Zero [16]
		(OffPtr <ptr.Type> ptr [s-16])
		(Zero [s-s%16] ptr mem))

// medium zeroing uses a duff device

			unlock(&mheap_.lock)
		})
		return false
	}

	if spc.sizeclass() != 0 {
		// Handle spans for small objects.
		if nfreed > 0 {
			// Only mark the span as needing zeroing if we've freed any
			// objects, because a fresh span that had been allocated into,
			// wasn't totally filled, but then swept, still has all of its
			// free slots zeroed.
			s.needzero = 1

	// ppc64le:`MOVW\s`
	// ppc64:`MOVWBR`
	b[(idx<<2)+3], b[(idx<<2)+2], b[(idx<<2)+1], b[(idx<<2)+0] = byte(val>>24), byte(val>>16), byte(val>>8), byte(val)
}

// ------------- //
//    Zeroing    //
// ------------- //

// Check that zero stores are combined into larger stores

func zero_byte_2(b1, b2 []byte) {
	// bounds checks to guarantee safety of writes below
	_, _ = b1[1], b2[1]

			(MOVOstoreconst [makeValAndOff(0,16)] destptr
				(MOVOstoreconst [makeValAndOff(0,0)] destptr mem))))

// Medium zeroing uses a duff device.
(Zero [s] destptr mem)
	&& s > 64 && s <= 1024 && s%16 == 0 && !config.noDuffDevice =>
	(DUFFZERO [s] destptr mem)

// Large zeroing uses REP STOSQ.
(Zero [s] destptr mem)
	&& (s > 1024 || (config.noDuffDevice && s > 64 || !config.useSSE && s > 32))
	&& s%8 == 0 =>