cmd/compile: generate makechan calls with int arguments

Where possible generate calls to runtime makechan with int arguments
during compile time instead of makechan with int64 arguments.

This eliminates converting arguments for calls to makechan with
int64 arguments for platforms where int64 values do not fit into
arguments of type int.

A similar optimization for makeslice was introduced in CL
golang.org/cl/27851.

386:
name                old time/op  new time/op  delta
MakeChan/Byte       52.4ns ± 6%  45.0ns ± 1%  -14.14%  (p=0.000 n=10+10)
MakeChan/Int        54.5ns ± 1%  49.1ns ± 1%   -9.87%  (p=0.000 n=10+10)
MakeChan/Ptr         150ns ± 1%   143ns ± 0%   -4.38%  (p=0.000 n=9+7)
MakeChan/Struct/0   49.2ns ± 2%  43.2ns ± 2%  -12.27%  (p=0.000 n=10+10)
MakeChan/Struct/32  81.7ns ± 2%  76.2ns ± 1%   -6.71%  (p=0.000 n=10+10)
MakeChan/Struct/40  88.4ns ± 2%  82.5ns ± 2%   -6.60%  (p=0.000 n=10+10)

AMD64:
name                old time/op  new time/op  delta
MakeChan/Byte       83.4ns ± 8%  80.8ns ± 3%    ~     (p=0.171 n=10+10)
MakeChan/Int         101ns ± 3%   101ns ± 2%    ~     (p=0.412 n=10+10)
MakeChan/Ptr         128ns ± 1%   128ns ± 1%    ~     (p=0.191 n=10+10)
MakeChan/Struct/0   67.6ns ± 3%  68.7ns ± 4%    ~     (p=0.224 n=10+10)
MakeChan/Struct/32   138ns ± 1%   139ns ± 1%    ~     (p=0.185 n=10+9)
MakeChan/Struct/40   154ns ± 1%   154ns ± 1%  -0.55%  (p=0.027 n=10+9)

Change-Id: Ie854cb066007232c5e9f71ea7d6fe27e81a9c050
Reviewed-on: https://go-review.googlesource.com/55140
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/test/makechan.go b/test/makechan.go
new file mode 100644
index 0000000000..0ac38c4b89
--- /dev/null
+++ b/test/makechan.go
@@ -0,0 +1,34 @@
+// errorcheck
+
+// Copyright 2017 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.
+
+// Ensure that typed non-integer, negative and to large
+// values are not accepted as size argument in make for
+// channels.
+
+package main
+
+type T chan byte
+
+var sink T
+
+func main() {
+	sink = make(T, -1)            // ERROR "negative buffer argument in make.*"
+	sink = make(T, uint64(1<<63)) // ERROR "buffer argument too large in make.*"
+
+	sink = make(T, 0.5) // ERROR "constant 0.5 truncated to integer"
+	sink = make(T, 1.0)
+	sink = make(T, float32(1.0)) // ERROR "non-integer buffer argument in make.*"
+	sink = make(T, float64(1.0)) // ERROR "non-integer buffer argument in make.*"
+	sink = make(T, 1.0)
+	sink = make(T, float32(1.0)) // ERROR "non-integer buffer argument in make.*"
+	sink = make(T, float64(1.0)) // ERROR "non-integer buffer argument in make.*"
+	sink = make(T, 1+0i)
+	sink = make(T, complex64(1+0i))  // ERROR "non-integer buffer argument in make.*"
+	sink = make(T, complex128(1+0i)) // ERROR "non-integer buffer argument in make.*"
+	sink = make(T, 1+0i)
+	sink = make(T, complex64(1+0i))  // ERROR "non-integer buffer argument in make.*"
+	sink = make(T, complex128(1+0i)) // ERROR "non-integer buffer argument in make.*"
+}