diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/cmd/compile/internal/walk/builtin.go | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/walk/builtin.go b/src/cmd/compile/internal/walk/builtin.go index 528296e99d..5c924a90c5 100644 --- a/src/cmd/compile/internal/walk/builtin.go +++ b/src/cmd/compile/internal/walk/builtin.go @@ -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) +} |