cmd/compile: handle integer conversions in static init inliner

Given code like

	func itou(i int) uint { return uint(i) }
	var x = itou(-1)

the static inliner from CL 450136 was rewriting the code to

	var x = uint(-1)

which is not valid Go code. Fix this by converting the
constants appropriately during inlining.

Fixes golang.org/x/image/vector test.

Change-Id: I13448df8504c6a70525b1cdc36e2c947e22cdd33
Reviewed-on: https://go-review.googlesource.com/c/go/+/451376
Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/compile/internal/staticinit/sched.go

@@ -7,6 +7,7 @@ package staticinit
 import (
 	"fmt"
 	"go/constant"
+	"go/token"
 
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/ir"
@@ -595,8 +596,11 @@ func (s *Schedule) staticAssignInlinedCall(l *ir.Name, loff int64, call *ir.Inli
 	for i, v := range as2init.Lhs {
 		args[v.(*ir.Name)] = as2init.Rhs[i]
 	}
-	r := subst(as2body.Rhs[0], args)
+	r, ok := subst(as2body.Rhs[0], args)
-	ok := s.StaticAssign(l, loff, r, typ)
+	if !ok {
+		return false
+	}
+	ok = s.StaticAssign(l, loff, r, typ)
 
 	if ok && base.Flag.Percent != 0 {
 		ir.Dump("static inlined-LEFT", l)
@@ -798,7 +802,8 @@ func isvaluelit(n ir.Node) bool {
 	return n.Op() == ir.OARRAYLIT || n.Op() == ir.OSTRUCTLIT
 }
 
-func subst(n ir.Node, m map[*ir.Name]ir.Node) ir.Node {
+func subst(n ir.Node, m map[*ir.Name]ir.Node) (ir.Node, bool) {
+	valid := true
 	var edit func(ir.Node) ir.Node
 	edit = func(x ir.Node) ir.Node {
 		switch x.Op() {
@@ -813,7 +818,51 @@ func subst(n ir.Node, m map[*ir.Name]ir.Node) ir.Node {
 		}
 		x = ir.Copy(x)
 		ir.EditChildren(x, edit)
+		if x, ok := x.(*ir.ConvExpr); ok && x.X.Op() == ir.OLITERAL {
+			// A conversion of variable or expression involving variables
+			// may become a conversion of constant after inlining the parameters
+			// and doing constant evaluation. Truncations that were valid
+			// on variables are not valid on constants, so we might have
+			// generated invalid code that will trip up the rest of the compiler.
+			// Fix those by truncating the constants.
+			if x, ok := truncate(x.X.(*ir.ConstExpr), x.Type()); ok {
+				return x
+			}
+			valid = false
+			return x
+		}
 		return typecheck.EvalConst(x)
 	}
-	return edit(n)
+	n = edit(n)
+	return n, valid
+}
+
+// truncate returns the result of force converting c to type t,
+// truncating its value as needed, like a conversion of a variable.
+// If the conversion is too difficult, truncate returns nil, false.
+func truncate(c *ir.ConstExpr, t *types.Type) (*ir.ConstExpr, bool) {
+	ct := c.Type()
+	cv := c.Val()
+	if ct.Kind() != t.Kind() {
+		switch {
+		default:
+			// Note: float -> float/integer and complex -> complex are valid but subtle.
+			// For example a float32(float64 1e300) evaluates to +Inf at runtime
+			// and the compiler doesn't have any concept of +Inf, so that would
+			// have to be left for runtime code evaluation.
+			// For now
+			return nil, false
+
+		case ct.IsInteger() && t.IsInteger():
+			// truncate or sign extend
+			bits := t.Size() * 8
+			cv = constant.BinaryOp(cv, token.AND, constant.MakeUint64(1<<bits-1))
+			if t.IsSigned() && constant.Compare(cv, token.GEQ, constant.MakeUint64(1<<(bits-1))) {
+				cv = constant.BinaryOp(cv, token.OR, constant.MakeInt64(-1<<(bits-1)))
+			}
+		}
+	}
+	c = ir.NewConstExpr(cv, c).(*ir.ConstExpr)
+	c.SetType(t)
+	return c, true
 }

test/convinline.go

@@ -0,0 +1,194 @@
+// runoutput
+//go:build !wasm
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"math"
+	"math/bits"
+	"os"
+	"strconv"
+	"strings"
+)
+
+var types = []string{
+	"int",
+	"int8",
+	"int16",
+	"int32",
+	"int64",
+	"uint",
+	"uint8",
+	"uint16",
+	"uint32",
+	"uint64",
+	"uintptr",
+	"float32",
+	"float64",
+}
+
+func main() {
+	var prog bytes.Buffer
+	fmt.Fprintf(&prog, "package main\n\n")
+	fmt.Fprintf(&prog, "import ( \"fmt\"; \"math\" )\n")
+	for _, t1 := range types {
+		for _, t2 := range types {
+			fmt.Fprintf(&prog, "func %[1]s_to_%[2]s(x %[1]s) %[2]s { return %[2]s(x) }\n", t1, t2)
+		}
+	}
+
+	var outputs []string
+	var exprs []string
+
+	fmt.Fprintf(&prog, "var (\n")
+	for _, t1 := range types {
+		var inputs []string
+		switch t1 {
+		case "int64", "int":
+			if t1 == "int64" || bits.UintSize == 64 {
+				inputs = append(inputs, "-0x8000_0000_0000_0000", "-0x7fff_ffff_ffff_ffff", "-0x12_3456_7890", "0x12_3456_7890", "0x7fff_ffff_ffff_ffff")
+			}
+			fallthrough
+		case "int32":
+			inputs = append(inputs, "-0x8000_0000", "-0x7fff_ffff", "-0x12_3456", "0x12_3456", "0x7fff_ffff")
+			fallthrough
+		case "int16":
+			inputs = append(inputs, "-0x8000", "-0x7fff", "-0x1234", "0x1234", "0x7fff")
+			fallthrough
+		case "int8":
+			inputs = append(inputs, "-0x80", "-0x7f", "-0x12", "-1", "0", "1", "0x12", "0x7f")
+
+		case "uint64", "uint", "uintptr":
+			if t1 == "uint64" || bits.UintSize == 64 {
+				inputs = append(inputs, "0x12_3456_7890", "0x7fff_ffff_ffff_ffff", "0x8000_0000_0000_0000", "0xffff_ffff_ffff_ffff")
+			}
+			fallthrough
+		case "uint32":
+			inputs = append(inputs, "0x12_3456", "0x7fff_ffff", "0x8000_0000", "0xffff_ffff")
+			fallthrough
+		case "uint16":
+			inputs = append(inputs, "0x1234", "0x7fff", "0x8000", "0xffff")
+			fallthrough
+		case "uint8":
+			inputs = append(inputs, "0", "1", "0x12", "0x7f", "0x80", "0xff")
+
+		case "float64":
+			inputs = append(inputs,
+				"-1.79769313486231570814527423731704356798070e+308",
+				"-1e300",
+				"-1e100",
+				"-1e40",
+				"-3.5e38",
+				"3.5e38",
+				"1e40",
+				"1e100",
+				"1e300",
+				"1.79769313486231570814527423731704356798070e+308")
+			fallthrough
+		case "float32":
+			inputs = append(inputs,
+				"-3.40282346638528859811704183484516925440e+38",
+				"-1e38",
+				"-1.5",
+				"-1.401298464324817070923729583289916131280e-45",
+				"0",
+				"1.401298464324817070923729583289916131280e-45",
+				"1.5",
+				"1e38",
+				"3.40282346638528859811704183484516925440e+38")
+		}
+		for _, t2 := range types {
+			for _, x := range inputs {
+				code := fmt.Sprintf("%s_to_%s(%s)", t1, t2, x)
+				fmt.Fprintf(&prog, "\tv%d = %s\n", len(outputs), code)
+				exprs = append(exprs, code)
+				outputs = append(outputs, convert(x, t1, t2))
+			}
+		}
+	}
+	fmt.Fprintf(&prog, ")\n\n")
+	fmt.Fprintf(&prog, "func main() {\n\tok := true\n")
+	for i, out := range outputs {
+		fmt.Fprintf(&prog, "\tif v%d != %s { fmt.Println(%q, \"=\", v%d, \"want\", %s); ok = false }\n", i, out, exprs[i], i, out)
+	}
+	fmt.Fprintf(&prog, "\tif !ok { println(\"FAIL\") }\n")
+	fmt.Fprintf(&prog, "}\n")
+
+	os.Stdout.Write(prog.Bytes())
+}
+
+func convert(x, t1, t2 string) string {
+	if strings.HasPrefix(t1, "int") {
+		v, err := strconv.ParseInt(x, 0, 64)
+		if err != nil {
+			println(x, t1, t2)
+			panic(err)
+		}
+		return convert1(v, t2)
+	}
+	if strings.HasPrefix(t1, "uint") {
+		v, err := strconv.ParseUint(x, 0, 64)
+		if err != nil {
+			println(x, t1, t2)
+			panic(err)
+		}
+		return convert1(v, t2)
+	}
+	if strings.HasPrefix(t1, "float") {
+		v, err := strconv.ParseFloat(x, 64)
+		if err != nil {
+			println(x, t1, t2)
+			panic(err)
+		}
+		if t1 == "float32" {
+			v = float64(float32(v))
+		}
+		return convert1(v, t2)
+	}
+	panic(t1)
+}
+
+func convert1[T int64 | uint64 | float64](v T, t2 string) string {
+	switch t2 {
+	case "int":
+		return fmt.Sprintf("%s(%#x)", t2, int(v))
+	case "int8":
+		return fmt.Sprintf("%s(%#x)", t2, int8(v))
+	case "int16":
+		return fmt.Sprintf("%s(%#x)", t2, int16(v))
+	case "int32":
+		return fmt.Sprintf("%s(%#x)", t2, int32(v))
+	case "int64":
+		return fmt.Sprintf("%s(%#x)", t2, int64(v))
+	case "uint":
+		return fmt.Sprintf("%s(%#x)", t2, uint(v))
+	case "uint8":
+		return fmt.Sprintf("%s(%#x)", t2, uint8(v))
+	case "uint16":
+		return fmt.Sprintf("%s(%#x)", t2, uint16(v))
+	case "uint32":
+		return fmt.Sprintf("%s(%#x)", t2, uint32(v))
+	case "uint64":
+		return fmt.Sprintf("%s(%#x)", t2, uint64(v))
+	case "uintptr":
+		return fmt.Sprintf("%s(%#x)", t2, uintptr(v))
+	case "float32":
+		v := float32(v)
+		if math.IsInf(float64(v), -1) {
+			return "float32(math.Inf(-1))"
+		}
+		if math.IsInf(float64(v), +1) {
+			return "float32(math.Inf(+1))"
+		}
+		return fmt.Sprintf("%s(%v)", t2, float64(v))
+	case "float64":
+		return fmt.Sprintf("%s(%v)", t2, float64(v))
+	}
+	panic(t2)
+}