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container/intsets: use fast popcount with gccgo

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Use the compiler intrinsic __builtin_popcount.

Change-Id: I58286fbcf66d1068390ea9caff2f98b8fe244c2d
Reviewed-on: https://go-review.googlesource.com/16831
Reviewed-by: Andrew Gerrand <adg@golang.org>
This commit is contained in:
Ian Lance Taylor 2015-11-10 17:38:53 -08:00
parent 3dedf801dd
commit d94e6fe0fd
3 changed files with 30 additions and 1 deletions
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9
container/intsets/popcnt_gccgo.go Normal file
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// 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.
// +build gccgo
package intsets
func popcount(x word) int

19
container/intsets/popcnt_gccgo_c.c Normal file
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// 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.
// +build gccgo
#include <errno.h>
#include <stdint.h>
#include <unistd.h>
#define _STRINGIFY2_(x) #x
#define _STRINGIFY_(x) _STRINGIFY2_(x)
#define GOSYM_PREFIX _STRINGIFY_(__USER_LABEL_PREFIX__)
extern intptr_t popcount(uintptr_t x) __asm__(GOSYM_PREFIX GOPKGPATH ".popcount");
intptr_t popcount(uintptr_t x) {
return __builtin_popcountl((unsigned long)(x));
}

3
container/intsets/popcnt_generic.go
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@ -2,7 +2,8 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build !amd64 appengine gccgo
// +build !amd64 appengine
// +build !gccgo
package intsets