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https://github.com/golang/go
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53 lines
826 B
Go
53 lines
826 B
Go
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// Copyright 2022 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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package p
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import (
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"fmt"
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"runtime"
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)
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var y int
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//go:noinline
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func Square(x int) {
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var pc0, pc1 [1]uintptr
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runtime.Callers(1, pc0[:]) // get PC at entry
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// a switch using jump table
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switch x {
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case 1:
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y = 1
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case 2:
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y = 4
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case 3:
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y = 9
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case 4:
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y = 16
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case 5:
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y = 25
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case 6:
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y = 36
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case 7:
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y = 49
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case 8:
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y = 64
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default:
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panic("too large")
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}
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// check PC is in the same function
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runtime.Callers(1, pc1[:])
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if pc1[0] < pc0[0] || pc1[0] > pc0[0]+1000000 {
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fmt.Printf("jump across DSO boundary. pc0=%x, pc1=%x\n", pc0[0], pc1[0])
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panic("FAIL")
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}
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if y != x*x {
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fmt.Printf("x=%d y=%d!=%d\n", x, y, x*x)
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panic("FAIL")
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}
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}
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