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cmd/asm: factor out line parsing from assembling

Currently cmd/asm's Parser.line both consumes a line of assembly from
the lexer and assembles it. This CL separates these two steps so that
the line parser can be reused for purposes other than generating a
Prog stream.

For #27539.
Updates #17544.

Change-Id: I452c9a2112fbcc1c94bf909efc0d1fcc71014812
Reviewed-on: https://go-review.googlesource.com/c/147097
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Austin Clements 2018-10-19 14:24:02 -04:00
parent 30cc978085
commit 52b2220559
2 changed files with 44 additions and 24 deletions

View File

@ -38,8 +38,7 @@ func testBadInstParser(t *testing.T, goarch string, tests []badInstTest) {
parser := NewParser(ctxt, arch, tokenizer)
err := tryParse(t, func() {
parser.start(lex.Tokenize(test.input))
parser.line()
parser.Parse()
})
switch {

View File

@ -91,7 +91,23 @@ func (p *Parser) pos() src.XPos {
}
func (p *Parser) Parse() (*obj.Prog, bool) {
for p.line() {
scratch := make([][]lex.Token, 0, 3)
for {
word, cond, operands, ok := p.line(scratch)
if !ok {
break
}
scratch = operands
if p.pseudo(word, operands) {
continue
}
i, present := p.arch.Instructions[word]
if present {
p.instruction(i, word, cond, operands)
continue
}
p.errorf("unrecognized instruction %q", word)
}
if p.errorCount > 0 {
return nil, false
@ -100,8 +116,17 @@ func (p *Parser) Parse() (*obj.Prog, bool) {
return p.firstProg, true
}
// WORD [ arg {, arg} ] (';' | '\n')
func (p *Parser) line() bool {
// line consumes a single assembly line from p.lex of the form
//
// {label:} WORD[.cond] [ arg {, arg} ] (';' | '\n')
//
// It adds any labels to p.pendingLabels and returns the word, cond,
// operand list, and true. If there is an error or EOF, it returns
// ok=false.
//
// line may reuse the memory from scratch.
func (p *Parser) line(scratch [][]lex.Token) (word, cond string, operands [][]lex.Token, ok bool) {
next:
// Skip newlines.
var tok lex.ScanToken
for {
@ -114,24 +139,29 @@ func (p *Parser) line() bool {
case '\n', ';':
continue
case scanner.EOF:
return false
return "", "", nil, false
}
break
}
// First item must be an identifier.
if tok != scanner.Ident {
p.errorf("expected identifier, found %q", p.lex.Text())
return false // Might as well stop now.
return "", "", nil, false // Might as well stop now.
}
word := p.lex.Text()
var cond string
operands := make([][]lex.Token, 0, 3)
word, cond = p.lex.Text(), ""
operands = scratch[:0]
// Zero or more comma-separated operands, one per loop.
nesting := 0
colon := -1
for tok != '\n' && tok != ';' {
// Process one operand.
items := make([]lex.Token, 0, 3)
var items []lex.Token
if cap(operands) > len(operands) {
// Reuse scratch items slice.
items = operands[:cap(operands)][len(operands)][:0]
} else {
items = make([]lex.Token, 0, 3)
}
for {
tok = p.lex.Next()
if len(operands) == 0 && len(items) == 0 {
@ -148,12 +178,12 @@ func (p *Parser) line() bool {
if tok == ':' {
// Labels.
p.pendingLabels = append(p.pendingLabels, word)
return true
goto next
}
}
if tok == scanner.EOF {
p.errorf("unexpected EOF")
return false
return "", "", nil, false
}
// Split operands on comma. Also, the old syntax on x86 for a "register pair"
// was AX:DX, for which the new syntax is DX, AX. Note the reordering.
@ -162,7 +192,7 @@ func (p *Parser) line() bool {
// Remember this location so we can swap the operands below.
if colon >= 0 {
p.errorf("invalid ':' in operand")
return true
return word, cond, operands, true
}
colon = len(operands)
}
@ -188,16 +218,7 @@ func (p *Parser) line() bool {
p.errorf("missing operand")
}
}
if p.pseudo(word, operands) {
return true
}
i, present := p.arch.Instructions[word]
if present {
p.instruction(i, word, cond, operands)
return true
}
p.errorf("unrecognized instruction %q", word)
return true
return word, cond, operands, true
}
func (p *Parser) instruction(op obj.As, word, cond string, operands [][]lex.Token) {