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cmd/6g: fix float32/64->uint64 conversion
CVTSS2SQ's rounding mode is controlled by the RC field of MXCSR; as we specifically need truncate semantic, we should use CVTTSS2SQ. Fixes #3804. R=rsc, r CC=golang-dev https://golang.org/cl/6352079
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@ -796,9 +796,9 @@ gmove(Node *f, Node *t)
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// algorithm is:
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// if small enough, use native float64 -> int64 conversion.
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// otherwise, subtract 2^63, convert, and add it back.
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a = ACVTSS2SQ;
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a = ACVTTSS2SQ;
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if(ft == TFLOAT64)
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a = ACVTSD2SQ;
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a = ACVTTSD2SQ;
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bignodes();
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regalloc(&r1, types[ft], N);
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regalloc(&r2, types[tt], t);
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105
test/fixedbugs/bug447.go
Normal file
105
test/fixedbugs/bug447.go
Normal file
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@ -0,0 +1,105 @@
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// runoutput
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// Copyright 2012 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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// Issue 3804
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// test all possible float -> integer conversions
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package main
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import (
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"bytes"
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"fmt"
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"strings"
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)
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var (
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intWidths = []int{8, 16, 32, 64} // int%d and uint%d
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floatWidths = []int{32, 64} // float%d
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)
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func main() {
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var names, funcs bytes.Buffer
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for _, iWidth := range intWidths {
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for _, typ := range []string{"int", "uint"} {
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var segs bytes.Buffer
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itype := fmt.Sprintf("%s%d", typ, iWidth)
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names.WriteString("\ttest" + itype + ",\n")
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for _, fWidth := range floatWidths {
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ftype := fmt.Sprintf("float%d", fWidth)
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seg := strings.Replace(testSegment, "$F", ftype, -1)
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seg = strings.Replace(seg, "$I", itype, -1)
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segs.WriteString(seg)
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}
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body := strings.Replace(testFunc, "$I", itype, -1)
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if typ[0] == 'u' {
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body = strings.Replace(body, "$TEST", " || i < 0", 1)
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} else {
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body = strings.Replace(body, "$TEST", "", 1)
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}
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body = strings.Replace(body, "$TESTSEGMENTS", segs.String(), 1)
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funcs.WriteString(body)
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}
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}
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program = strings.Replace(program, "$NAMES", names.String(), 1)
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program = strings.Replace(program, "$FUNCS", funcs.String(), 1)
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fmt.Print(program)
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}
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const testSegment = `
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f$F := $F(f)
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if math.Abs(float64(f$F) - f) < 0.05 {
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if v := $I(f$F); v != $I(i) {
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fmt.Printf("$I($F(%f)) = %v, expected %v\n", f, v, i)
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}
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}`
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const testFunc =
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`func test$I(f float64, i int64) {
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if i != int64($I(i))$TEST {
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return
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}
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$TESTSEGMENTS
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}
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`
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var program =
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`package main
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import (
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"fmt"
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"math"
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)
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var tests = []struct {
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f float64
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i int64
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}{
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{39.7, 39},
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{-39.7, -39},
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{258.6, 258},
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{-258.6, -258},
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{65538.9, 65538},
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{-65538.9, -65538},
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{4294967298.8, 4294967298},
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{-4294967298.8, -4294967298},
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}
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var funcs = []func(float64, int64){
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$NAMES
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}
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$FUNCS
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func main() {
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for _, t := range tests {
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for _, f := range funcs {
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f(t.f, t.i)
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}
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}
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}
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`
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