duplicate symbols and the linker will fail. To avoid this, definitions
must be placed in preambles in other files, or in C source files.

# Passing pointers

Go is a garbage collected language, and the garbage collector needs to
know the location of every pointer to Go memory. Because of this,
there are restrictions on passing pointers between Go and C.

In this section the term Go pointer means a pointer to memory

	SRLI	$1, X5, F1			// ERROR "expected integer register in rd position but got non-integer register F1"
	SRLI	$1, F1, X5			// ERROR "expected integer register in rs1 position but got non-integer register F1"
	FNES	F1, (X5)			// ERROR "needs an integer register output"

func (b *Buffer) Reset() {
	b.buf = b.buf[:0]
	b.off = 0
	b.lastRead = opInvalid
}

// tryGrowByReslice is an inlineable version of grow for the fast-case where the
// internal buffer only needs to be resliced.
// It returns the index where bytes should be written and whether it succeeded.
func (b *Buffer) tryGrowByReslice(n int) (int, bool) {
	if l := len(b.buf); n <= cap(b.buf)-l {
		b.buf = b.buf[:l+n]

			}
		}
	}
	return false
}

// rewriteCalls rewrites all calls that pass pointers to check that
// they follow the rules for passing pointers between Go and C.
// This reports whether the package needs to import unsafe as _cgo_unsafe.
func (p *Package) rewriteCalls(f *File) bool {
	needsUnsafe := false
	// Walk backward so that in C.f1(C.f2()) we rewrite C.f2 first.
	for _, call := range f.Calls {
		if call.Done {

			if scale != 0 {
				p.errorf("expected simple register reference")
			}
			a.Type = obj.TYPE_REG
			a.Reg = r1
			if r2 != 0 {
				// Form is R1:R2. It is on RHS and the second register
				// needs to go into the LHS.
				panic("cannot happen (Addr.Reg2)")
			}
		}
		// fmt.Printf("REG %s\n", obj.Dconv(&emptyProg, 0, a))
		p.expectOperandEnd()
		return
	}

	// Constant.

	var flag = int64(0)
	if len(operands) == 3 {
		flag = p.evalInteger("TEXT", operands[1])
		next++
	}

	// Issue an error if we see a function defined as ABIInternal
	// without NOSPLIT. In ABIInternal, obj needs to know the function
	// signature in order to construct the morestack path, so this
	// currently isn't supported for asm functions.
	if nameAddr.Sym.ABI() == obj.ABIInternal && flag&obj.NOSPLIT == 0 {

type urlFrag struct {
	url, frag string
}

var (
	mu          sync.Mutex
	crawled     = make(map[string]bool)      // URL without fragment -> true
	neededFrags = make(map[urlFrag][]string) // URL#frag -> who needs it
)

var aRx = regexp.MustCompile(`<a href=['"]?(/[^\s'">]+)`)

// Owned by crawlLoop goroutine:
var (
	linkSources = make(map[string][]string) // url no fragment -> sources
	fragExists  = make(map[urlFrag]bool)

package bytes_test

import (
	"bytes"
	"encoding/base64"
	"fmt"
	"io"
	"os"
	"sort"
	"strconv"
	"unicode"
)

func ExampleBuffer() {
	var b bytes.Buffer // A Buffer needs no initialization.
	b.Write([]byte("Hello "))
	fmt.Fprintf(&b, "world!")
	b.WriteTo(os.Stdout)
	// Output: Hello world!
}

func ExampleBuffer_reader() {
	// A Buffer can turn a string or a []byte into an io.Reader.

Some of the details map precisely to the machine, but some do not.
This is because the compiler suite (see
<a href="https://9p.io/sys/doc/compiler.html">this description</a>)
needs no assembler pass in the usual pipeline.
Instead, the compiler operates on a kind of semi-abstract instruction set,
and instruction selection occurs partly after code generation.
The assembler works on the semi-abstract form, so

	"CALL":  true,
	"CBZ":   true,
	"CBZW":  true,
	"CBNZ":  true,
	"CBNZW": true,
	"JMP":   true,
	"TBNZ":  true,
	"TBZ":   true,

	// ADR isn't really a jump, but it takes a PC or label reference,
	// which needs to patched like a jump.
	"ADR":  true,
	"ADRP": true,
}

func jumpArm64(word string) bool {
	return arm64Jump[word]
}

var arm64SpecialOperand map[string]arm64.SpecialOperand