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cmd/compile: avoid slicebytetostring call in len(string([]byte))

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Change-Id: Ie04503e61400a793a6a29a4b58795254deabe472
Reviewed-on: https://go-review.googlesource.com/c/go/+/497276
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
Cuong Manh Le 2023-05-23 11:23:48 +07:00 committed by Gopher Robot
parent 3651d8e516
commit 35a71dc56d
2 changed files with 15 additions and 0 deletions
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10
src/cmd/compile/internal/walk/builtin.go
View File

@ -250,6 +250,10 @@ func walkLenCap(n *ir.UnaryExpr, init *ir.Nodes) ir.Node {
// Replace len([]rune(string)) with runtime.countrunes(string).
return mkcall("countrunes", n.Type(), init, typecheck.Conv(n.X.(*ir.ConvExpr).X, types.Types[types.TSTRING]))
}
if isByteCount(n) {
_, len := backingArrayPtrLen(cheapExpr(n.X.(*ir.ConvExpr).X, init))
return len
}
n.X = walkExpr(n.X, init)
@ -862,3 +866,9 @@ func writebarrierfn(name string, l *types.Type, r *types.Type) ir.Node {
func isRuneCount(n ir.Node) bool {
return base.Flag.N == 0 && !base.Flag.Cfg.Instrumenting && n.Op() == ir.OLEN && n.(*ir.UnaryExpr).X.Op() == ir.OSTR2RUNES
}
// isByteCount reports whether n is of the form len(string([]byte)).
func isByteCount(n ir.Node) bool {
return base.Flag.N == 0 && !base.Flag.Cfg.Instrumenting && n.Op() == ir.OLEN &&
(n.(*ir.UnaryExpr).X.Op() == ir.OBYTES2STR || n.(*ir.UnaryExpr).X.Op() == ir.OBYTES2STRTMP)
}

5
test/codegen/strings.go
View File

@ -14,6 +14,11 @@ func CountRunes(s string) int { // Issue #24923
return len([]rune(s))
}
func CountBytes(s []byte) int {
// amd64:-`.*runtime.slicebytetostring`
return len(string(s))
}
func ToByteSlice() []byte { // Issue #24698
// amd64:`LEAQ\ttype:\[3\]uint8`
// amd64:`CALL\truntime\.newobject`