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* This is an improved version of an earlier patch. * Verified with gcc up to 100. * Limited to two instructions based on costs from https://gmplib.org/~tege/x86-timing.pdf Change-Id: Ib7c37de6fd8e0ba554459b15c7409508cbcf6728 Reviewed-on: https://go-review.googlesource.com/21103 Reviewed-by: Keith Randall <khr@golang.org> Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro> TryBot-Result: Gobot Gobot <gobot@golang.org>
46 lines
1 KiB
Go
46 lines
1 KiB
Go
// runoutput
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// Copyright 2016 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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// Generate test of strength reduction for multiplications
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// with contstants. Especially useful for amd64/386.
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package main
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import "fmt"
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func testMul(fact, bits int) string {
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n := fmt.Sprintf("testMul_%d_%d", fact, bits)
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fmt.Printf("func %s(s int%d) {\n", n, bits)
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want := 0
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for i := 0; i < 200; i++ {
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fmt.Printf(` if want, got := int%d(%d), s*%d; want != got {
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failed = true
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fmt.Printf("got %d * %%d == %%d, wanted %d\n", s, got)
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}
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`, bits, want, i, i, want)
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want += fact
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}
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fmt.Printf("}\n")
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return fmt.Sprintf("%s(%d)", n, fact)
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}
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func main() {
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fmt.Printf("package main\n")
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fmt.Printf("import \"fmt\"\n")
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fmt.Printf("var failed = false\n")
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f1 := testMul(17, 32)
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f2 := testMul(131, 64)
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fmt.Printf("func main() {\n")
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fmt.Println(f1)
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fmt.Println(f2)
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fmt.Printf("if failed {\n panic(\"multiplication failed\")\n}\n")
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fmt.Printf("}\n")
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}
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