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cmd/gc: reduce lexer allocs when parsing numeric constants

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This reduces the number of allocs when
running the rotate.go tests by
about 20%, after applying CL 5700.

Combining

s = "const str"
s += <another string>

generally saves an alloc and might be a candidate for
rsc's grind tool. However, I'm sending this CL now
because this also reuses the result of calling lexbuf.String.

Change-Id: If3a7300b7da9612ab62bb910ee90349dca88dde3
Reviewed-on: https://go-review.googlesource.com/5821
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Josh Bleecher Snyder 2015-02-24 20:54:57 +00:00
parent 1d4bfb3ebb
commit 9f4c25e223
1 changed files with 10 additions and 9 deletions
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19
src/cmd/internal/gc/lex.go
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@ -853,6 +853,7 @@ func _yylex(yylval *yySymType) int32 {
var rune_ uint
var s *Sym
var h *Loophack
var str string
prevlineno = lineno
@ -1405,8 +1406,9 @@ ncu:
cp = nil
ungetc(c)
str = lexbuf.String()
yylval.val.U.Xval = new(Mpint)
mpatofix(yylval.val.U.Xval, lexbuf.String())
mpatofix(yylval.val.U.Xval, str)
if yylval.val.U.Xval.Ovf != 0 {
Yyerror("overflow in constant")
Mpmovecfix(yylval.val.U.Xval, 0)
@ -1416,8 +1418,7 @@ ncu:
if Debug['x'] != 0 {
fmt.Printf("lex: integer literal\n")
}
litbuf = "literal "
litbuf += lexbuf.String()
litbuf = "literal " + str
return LLITERAL
casedot:
@ -1461,9 +1462,10 @@ caseep:
casei:
cp = nil
str = lexbuf.String()
yylval.val.U.Cval = new(Mpcplx)
Mpmovecflt(&yylval.val.U.Cval.Real, 0.0)
mpatoflt(&yylval.val.U.Cval.Imag, lexbuf.String())
mpatoflt(&yylval.val.U.Cval.Imag, str)
if yylval.val.U.Cval.Imag.Val.Ovf != 0 {
Yyerror("overflow in imaginary constant")
Mpmovecflt(&yylval.val.U.Cval.Real, 0.0)
@ -1473,16 +1475,16 @@ casei:
if Debug['x'] != 0 {
fmt.Printf("lex: imaginary literal\n")
}
litbuf = "literal "
litbuf += lexbuf.String()
litbuf = "literal " + str
return LLITERAL
caseout:
cp = nil
ungetc(c)
str = lexbuf.String()
yylval.val.U.Fval = new(Mpflt)
mpatoflt(yylval.val.U.Fval, lexbuf.String())
mpatoflt(yylval.val.U.Fval, str)
if yylval.val.U.Fval.Val.Ovf != 0 {
Yyerror("overflow in float constant")
Mpmovecflt(yylval.val.U.Fval, 0.0)
@ -1492,8 +1494,7 @@ caseout:
if Debug['x'] != 0 {
fmt.Printf("lex: floating literal\n")
}
litbuf = "literal "
litbuf += lexbuf.String()
litbuf = "literal " + str
return LLITERAL
strlit: