e0f69f36ea
Previously the libgo Makefile explicitly listed the set of files to
compile for each package. For packages that use build tags, this
required a lot of awkward automake conditionals in the Makefile.
This CL changes the build to look at the build tags in the files.
The new shell script libgo/match.sh does the matching. This required
adjusting a lot of build tags, and removing some files that are never
used. I verified that the exact same sets of files are compiled on
amd64 GNU/Linux. I also tested the build on i386 Solaris.
Writing match.sh revealed some bugs in the build tag handling that
already exists, in a slightly different form, in the gotest shell
script. This CL fixes those problems as well.
The old code used automake conditionals to handle systems that were
missing strerror_r and wait4. Rather than deal with those in Go, those
functions are now implemented in runtime/go-nosys.c when necessary, so
the Go code can simply assume that they exist.
The os testsuite looked for dir_unix.go, which was never built for gccgo
and has now been removed. I changed the testsuite to look for dir.go
instead.
Reviewed-on: https://go-review.googlesource.com/25546
From-SVN: r239189
36 lines
1.5 KiB
Go
36 lines
1.5 KiB
Go
// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build ignore
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package runtime
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import "unsafe"
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// fastlog2 implements a fast approximation to the base 2 log of a
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// float64. This is used to compute a geometric distribution for heap
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// sampling, without introducing dependences into package math. This
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// uses a very rough approximation using the float64 exponent and the
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// first 25 bits of the mantissa. The top 5 bits of the mantissa are
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// used to load limits from a table of constants and the rest are used
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// to scale linearly between them.
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func fastlog2(x float64) float64 {
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const fastlogScaleBits = 20
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const fastlogScaleRatio = 1.0 / (1 << fastlogScaleBits)
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xBits := float64bits(x)
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// Extract the exponent from the IEEE float64, and index a constant
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// table with the first 10 bits from the mantissa.
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xExp := int64((xBits>>52)&0x7FF) - 1023
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xManIndex := (xBits >> (52 - fastlogNumBits)) % (1 << fastlogNumBits)
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xManScale := (xBits >> (52 - fastlogNumBits - fastlogScaleBits)) % (1 << fastlogScaleBits)
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low, high := fastlog2Table[xManIndex], fastlog2Table[xManIndex+1]
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return float64(xExp) + low + (high-low)*float64(xManScale)*fastlogScaleRatio
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}
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// float64bits returns the IEEE 754 binary representation of f.
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// Taken from math.Float64bits to avoid dependences into package math.
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func float64bits(f float64) uint64 { return *(*uint64)(unsafe.Pointer(&f)) }
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