mirror of git://gcc.gnu.org/git/gcc.git
48 lines
1.6 KiB
Go
48 lines
1.6 KiB
Go
// Copyright 2009 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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// Malloc small size classes.
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//
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// See malloc.go for overview.
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// See also mksizeclasses.go for how we decide what size classes to use.
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package runtime
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// sizeToClass(0 <= n <= MaxSmallSize) returns the size class,
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// 1 <= sizeclass < NumSizeClasses, for n.
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// Size class 0 is reserved to mean "not small".
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//
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// The sizeToClass lookup is implemented using two arrays,
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// one mapping sizes <= 1024 to their class and one mapping
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// sizes >= 1024 and <= MaxSmallSize to their class.
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// All objects are 8-aligned, so the first array is indexed by
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// the size divided by 8 (rounded up). Objects >= 1024 bytes
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// are 128-aligned, so the second array is indexed by the
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// size divided by 128 (rounded up). The arrays are constants
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// in sizeclass.go generated by mksizeclass.go.
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func sizeToClass(size uint32) uint32 {
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if size > _MaxSmallSize {
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throw("invalid size")
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}
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if size > smallSizeMax-8 {
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return uint32(size_to_class128[(size-smallSizeMax+largeSizeDiv-1)/largeSizeDiv])
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}
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return uint32(size_to_class8[(size+smallSizeDiv-1)/smallSizeDiv])
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}
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// Returns size of the memory block that mallocgc will allocate if you ask for the size.
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func roundupsize(size uintptr) uintptr {
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if size < _MaxSmallSize {
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if size <= smallSizeMax-8 {
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return uintptr(class_to_size[size_to_class8[(size+smallSizeDiv-1)/smallSizeDiv]])
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} else {
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return uintptr(class_to_size[size_to_class128[(size-smallSizeMax+largeSizeDiv-1)/largeSizeDiv]])
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}
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}
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if size+_PageSize < size {
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return size
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}
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return round(size, _PageSize)
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}
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