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go/ssa/interp: implement min/max builtins
Updates golang/go#59488. Change-Id: I68c90ddf0f9dea2c6506b9ab43beb522cbdf5fdd Reviewed-on: https://go-review.googlesource.com/c/tools/+/497516 Run-TryBot: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> gopls-CI: kokoro <noreply+kokoro@google.com> Reviewed-by: Tim King <taking@google.com>
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‎go/ssa/interp/external.go‎

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@@ -70,6 +70,7 @@ func init() {
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"bytes.IndexByte": ext۰bytes۰IndexByte,
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"fmt.Sprint": ext۰fmt۰Sprint,
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"math.Abs": ext۰math۰Abs,
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"math.Copysign": ext۰math۰Copysign,
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"math.Exp": ext۰math۰Exp,
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"math.Float32bits": ext۰math۰Float32bits,
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"math.Float32frombits": ext۰math۰Float32frombits,
@@ -158,6 +159,10 @@ func ext۰math۰Abs(fr *frame, args []value) value {
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return math.Abs(args[0].(float64))
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}
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func ext۰math۰Copysign(fr *frame, args []value) value {
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return math.Copysign(args[0].(float64), args[1].(float64))
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}
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func ext۰math۰Exp(fr *frame, args []value) value {
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return math.Exp(args[0].(float64))
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}

‎go/ssa/interp/interp_go121_test.go‎

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@@ -0,0 +1,12 @@
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// Copyright 2023 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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//go:build go1.21
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// +build go1.21
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package interp_test
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func init() {
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testdataTests = append(testdataTests, "minmax.go")
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}

‎go/ssa/interp/ops.go‎

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@@ -1060,6 +1060,11 @@ func callBuiltin(caller *frame, callpos token.Pos, fn *ssa.Builtin, args []value
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panic(fmt.Sprintf("cap: illegal operand: %T", x))
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}
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case "min":
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return foldLeft(min, args)
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case "max":
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return foldLeft(max, args)
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case "real":
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switch c := args[0].(type) {
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case complex64:
@@ -1426,3 +1431,89 @@ func checkInterface(i *interpreter, itype *types.Interface, x iface) string {
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}
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return "" // ok
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}
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func foldLeft(op func(value, value) value, args []value) value {
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x := args[0]
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for _, arg := range args[1:] {
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x = op(x, arg)
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}
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return x
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}
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func min(x, y value) value {
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switch x := x.(type) {
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case float32:
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return fmin(x, y.(float32))
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case float64:
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return fmin(x, y.(float64))
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}
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// return (y < x) ? y : x
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if binop(token.LSS, nil, y, x).(bool) {
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return y
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}
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return x
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}
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func max(x, y value) value {
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switch x := x.(type) {
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case float32:
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return fmax(x, y.(float32))
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case float64:
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return fmax(x, y.(float64))
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}
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// return (y > x) ? y : x
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if binop(token.GTR, nil, y, x).(bool) {
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return y
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}
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return x
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}
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// copied from $GOROOT/src/runtime/minmax.go
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type floaty interface{ ~float32 | ~float64 }
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func fmin[F floaty](x, y F) F {
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if y != y || y < x {
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return y
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}
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if x != x || x < y || x != 0 {
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return x
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}
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// x and y are both ±0
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// if either is -0, return -0; else return +0
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return forbits(x, y)
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}
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func fmax[F floaty](x, y F) F {
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if y != y || y > x {
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return y
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}
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if x != x || x > y || x != 0 {
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return x
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}
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// x and y are both ±0
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// if both are -0, return -0; else return +0
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return fandbits(x, y)
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}
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func forbits[F floaty](x, y F) F {
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switch unsafe.Sizeof(x) {
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case 4:
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*(*uint32)(unsafe.Pointer(&x)) |= *(*uint32)(unsafe.Pointer(&y))
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case 8:
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*(*uint64)(unsafe.Pointer(&x)) |= *(*uint64)(unsafe.Pointer(&y))
1507+
}
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return x
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}
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func fandbits[F floaty](x, y F) F {
1512+
switch unsafe.Sizeof(x) {
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case 4:
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*(*uint32)(unsafe.Pointer(&x)) &= *(*uint32)(unsafe.Pointer(&y))
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case 8:
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*(*uint64)(unsafe.Pointer(&x)) &= *(*uint64)(unsafe.Pointer(&y))
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}
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return x
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}

‎go/ssa/interp/testdata/minmax.go‎

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@@ -0,0 +1,118 @@
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// Copyright 2023 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 main
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import (
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"fmt"
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"math"
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)
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func main() {
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TestMinFloat()
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TestMaxFloat()
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TestMinMaxInt()
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TestMinMaxUint8()
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TestMinMaxString()
18+
}
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func errorf(format string, args ...any) { panic(fmt.Sprintf(format, args...)) }
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func fatalf(format string, args ...any) { panic(fmt.Sprintf(format, args...)) }
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// derived from $GOROOT/src/runtime/minmax_test.go
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var (
26+
zero = math.Copysign(0, +1)
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negZero = math.Copysign(0, -1)
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inf = math.Inf(+1)
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negInf = math.Inf(-1)
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nan = math.NaN()
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)
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var tests = []struct{ min, max float64 }{
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{1, 2},
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{-2, 1},
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{negZero, zero},
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{zero, inf},
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{negInf, zero},
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{negInf, inf},
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{1, inf},
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{negInf, 1},
42+
}
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var all = []float64{1, 2, -1, -2, zero, negZero, inf, negInf, nan}
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func eq(x, y float64) bool {
47+
return x == y && math.Signbit(x) == math.Signbit(y)
48+
}
49+
50+
func TestMinFloat() {
51+
for _, tt := range tests {
52+
if z := min(tt.min, tt.max); !eq(z, tt.min) {
53+
errorf("min(%v, %v) = %v, want %v", tt.min, tt.max, z, tt.min)
54+
}
55+
if z := min(tt.max, tt.min); !eq(z, tt.min) {
56+
errorf("min(%v, %v) = %v, want %v", tt.max, tt.min, z, tt.min)
57+
}
58+
}
59+
for _, x := range all {
60+
if z := min(nan, x); !math.IsNaN(z) {
61+
errorf("min(%v, %v) = %v, want %v", nan, x, z, nan)
62+
}
63+
if z := min(x, nan); !math.IsNaN(z) {
64+
errorf("min(%v, %v) = %v, want %v", nan, x, z, nan)
65+
}
66+
}
67+
}
68+
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func TestMaxFloat() {
70+
for _, tt := range tests {
71+
if z := max(tt.min, tt.max); !eq(z, tt.max) {
72+
errorf("max(%v, %v) = %v, want %v", tt.min, tt.max, z, tt.max)
73+
}
74+
if z := max(tt.max, tt.min); !eq(z, tt.max) {
75+
errorf("max(%v, %v) = %v, want %v", tt.max, tt.min, z, tt.max)
76+
}
77+
}
78+
for _, x := range all {
79+
if z := max(nan, x); !math.IsNaN(z) {
80+
errorf("min(%v, %v) = %v, want %v", nan, x, z, nan)
81+
}
82+
if z := max(x, nan); !math.IsNaN(z) {
83+
errorf("min(%v, %v) = %v, want %v", nan, x, z, nan)
84+
}
85+
}
86+
}
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// testMinMax tests that min/max behave correctly on every pair of
89+
// values in vals.
90+
//
91+
// vals should be a sequence of values in strictly ascending order.
92+
func testMinMax[T int | uint8 | string](vals ...T) {
93+
for i, x := range vals {
94+
for _, y := range vals[i+1:] {
95+
if !(x < y) {
96+
fatalf("values out of order: !(%v < %v)", x, y)
97+
}
98+
99+
if z := min(x, y); z != x {
100+
errorf("min(%v, %v) = %v, want %v", x, y, z, x)
101+
}
102+
if z := min(y, x); z != x {
103+
errorf("min(%v, %v) = %v, want %v", y, x, z, x)
104+
}
105+
106+
if z := max(x, y); z != y {
107+
errorf("max(%v, %v) = %v, want %v", x, y, z, y)
108+
}
109+
if z := max(y, x); z != y {
110+
errorf("max(%v, %v) = %v, want %v", y, x, z, y)
111+
}
112+
}
113+
}
114+
}
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func TestMinMaxInt() { testMinMax[int](-7, 0, 9) }
117+
func TestMinMaxUint8() { testMinMax[uint8](0, 1, 2, 4, 7) }
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func TestMinMaxString() { testMinMax[string]("a", "b", "c") }

‎go/ssa/interp/testdata/src/math/math.go‎

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Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
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package math
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func Copysign(float64, float64) float64
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func NaN() float64
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func Inf(int) float64

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