From 42fcc6fea03673eeed1447eaab78a7df9385246e Mon Sep 17 00:00:00 2001 From: Josh Bleecher Snyder Date: Thu, 19 Mar 2015 09:28:02 -0700 Subject: [PATCH] cmd/internal/gc: add internConcat for alloc-free string concatenation This is a follow-up to review comments on CL 7696. I believe that this includes the first regular Go test in the compiler. No functional changes. Passes toolstash -cmp. Change-Id: Id45f51aa664c5d52ece2a61cd7d8417159ce3cf0 Reviewed-on: https://go-review.googlesource.com/7820 Reviewed-by: Brad Fitzpatrick --- src/cmd/internal/gc/lex.go | 9 +++++++++ src/cmd/internal/gc/lex_test.go | 22 ++++++++++++++++++++++ src/cmd/internal/gc/subr.go | 6 +++--- src/cmd/internal/gc/walk.go | 19 ++++++++++--------- 4 files changed, 44 insertions(+), 12 deletions(-) create mode 100644 src/cmd/internal/gc/lex_test.go diff --git a/src/cmd/internal/gc/lex.go b/src/cmd/internal/gc/lex.go index 7470a1ff3a1..623c9a1d93e 100644 --- a/src/cmd/internal/gc/lex.go +++ b/src/cmd/internal/gc/lex.go @@ -1511,6 +1511,15 @@ func internString(b []byte) string { return s } +func internConcat(ss ...string) string { + const bufsiz = 128 // big enough for most compiler uses; must be constant to avoid heap alloc + b := make([]byte, 0, bufsiz) + for _, s := range ss { + b = append(b, s...) + } + return internString(b) +} + func more(pp *string) bool { p := *pp for p != "" && yy_isspace(int(p[0])) { diff --git a/src/cmd/internal/gc/lex_test.go b/src/cmd/internal/gc/lex_test.go new file mode 100644 index 00000000000..845a9d8c36e --- /dev/null +++ b/src/cmd/internal/gc/lex_test.go @@ -0,0 +1,22 @@ +// Copyright 2015 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package gc + +import "testing" + +func TestInternConcat(t *testing.T) { + fromKind := "T" + toKind := "E" + var s string + n := testing.AllocsPerRun(100, func() { + s = internConcat("conv", fromKind, "2", toKind) + }) + if s != "convT2E" { + t.Fatalf("internConcat(\"conv\", \"T\", \"2\", \"E\")=%q want %q", s, "convT2E") + } + if n > 0 { + t.Errorf("internConcat allocs per run=%f", n) + } +} diff --git a/src/cmd/internal/gc/subr.go b/src/cmd/internal/gc/subr.go index 32486c77bb8..43aa382206b 100644 --- a/src/cmd/internal/gc/subr.go +++ b/src/cmd/internal/gc/subr.go @@ -3574,10 +3574,10 @@ func isdirectiface(t *Type) bool { return false } -// type2IET returns "T" if t is a concrete type, -// "I" if t is an interface type, and "E" if t is an empty interface type. +// IET returns "T" if t is a concrete type, "I" if t is an interface type, and +// "E" if t is an empty interface type. // It is used to build calls to the conv* and assert* runtime routines. -func type2IET(t *Type) string { +func (t *Type) IET() string { if isnilinter(t) { return "E" } diff --git a/src/cmd/internal/gc/walk.go b/src/cmd/internal/gc/walk.go index 2784648a858..591974d18b2 100644 --- a/src/cmd/internal/gc/walk.go +++ b/src/cmd/internal/gc/walk.go @@ -678,7 +678,7 @@ func walkexpr(np **Node, init **NodeList) { n1 := Nod(OADDR, n.Left, nil) r := n.Right // i.(T) - buf := "assert" + type2IET(r.Left.Type) + "2" + type2IET(r.Type) + buf := internConcat("assert", r.Left.Type.IET(), "2", r.Type.IET()) fn := syslook(buf, 1) substArgTypes(fn, r.Left.Type, r.Type) @@ -869,8 +869,8 @@ func walkexpr(np **Node, init **NodeList) { oktype = ok.Type } - fromKind := type2IET(from.Type) - toKind := type2IET(t) + fromKind := from.Type.IET() + toKind := t.IET() // Avoid runtime calls in a few cases of the form _, ok := i.(T). // This is faster and shorter and allows the corresponding assertX2X2 @@ -903,7 +903,7 @@ func walkexpr(np **Node, init **NodeList) { } resptr.Etype = 1 // addr does not escape - buf := "assert" + fromKind + "2" + toKind + "2" + buf := internConcat("assert", fromKind, "2", toKind, "2") fn := syslook(buf, 1) substArgTypes(fn, from.Type, t) call := mkcall1(fn, oktype, init, typename(t), from, resptr) @@ -927,11 +927,7 @@ func walkexpr(np **Node, init **NodeList) { goto ret } - // Build name of function: convI2E etc. - // Not all names are possible - // (e.g., we'll never generate convE2E or convE2I). - buf := "conv" + type2IET(n.Left.Type) + "2" + type2IET(n.Type) - fn := syslook(buf, 1) + // Handle fast paths and special cases. var ll *NodeList if !Isinter(n.Left.Type) { ll = list(ll, typename(n.Left.Type)) @@ -1010,6 +1006,11 @@ func walkexpr(np **Node, init **NodeList) { } } + // Build name of function: convI2E etc. + // Not all names are possible + // (e.g., we'll never generate convE2E or convE2I). + buf := internConcat("conv", n.Left.Type.IET(), "2", n.Type.IET()) + fn := syslook(buf, 1) substArgTypes(fn, n.Left.Type, n.Type) dowidth(fn.Type) n = Nod(OCALL, fn, nil)