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cmd/compile: fixes for non-constant Sizeof/Alignof/Offsetof

Includes Robert's suggested fix in validate.go to not fail on
non-constant alignof/offsetof/sizeof calls. Further changes to wait on
transforming these calls until stenciling time, when we can call
EvalConst() to evaluate them once all the relevant types are known.

Added a bunch of new tests for non-constant Sizeof/Alignof/Offsetof.

Fixes #47716

Change-Id: I469af888eb9ce3a853124d919eda753971009b3e
Reviewed-on: https://go-review.googlesource.com/c/go/+/344250
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Trust: Dan Scales <danscales@google.com>
This commit is contained in:
Dan Scales 2021-08-22 11:50:58 -07:00
parent 8157960d7f
commit be1a693477
6 changed files with 95 additions and 5 deletions

View File

@ -138,10 +138,18 @@ func Call(pos src.XPos, typ *types.Type, fun ir.Node, args []ir.Node, dots bool)
// until arg type known
// OAPPEND: transformAppend requires that the arg is a slice
// ODELETE: transformDelete requires that the arg is a map
// OALIGNOF, OSIZEOF: can be eval'ed to a constant until types known.
switch fun.BuiltinOp {
case ir.OMAKE, ir.OREAL, ir.OIMAG, ir.OAPPEND, ir.ODELETE:
case ir.OMAKE, ir.OREAL, ir.OIMAG, ir.OAPPEND, ir.ODELETE, ir.OALIGNOF, ir.OOFFSETOF, ir.OSIZEOF:
hasTParam := false
for _, arg := range args {
if fun.BuiltinOp == ir.OOFFSETOF {
// It's the type of left operand of the
// selection that matters, not the type of
// the field itself (which is irrelevant for
// offsetof).
arg = arg.(*ir.SelectorExpr).X
}
if arg.Type().HasTParam() {
hasTParam = true
break

View File

@ -1037,7 +1037,7 @@ func (subst *subster) node(n ir.Node) ir.Node {
name := call.X.Name()
if name.BuiltinOp != ir.OXXX {
switch name.BuiltinOp {
case ir.OMAKE, ir.OREAL, ir.OIMAG, ir.OAPPEND, ir.ODELETE:
case ir.OMAKE, ir.OREAL, ir.OIMAG, ir.OAPPEND, ir.ODELETE, ir.OALIGNOF, ir.OOFFSETOF, ir.OSIZEOF:
// Transform these builtins now that we
// know the type of the args.
m = transformBuiltin(call)

View File

@ -811,7 +811,10 @@ func transformBuiltin(n *ir.CallExpr) ir.Node {
return transformRealImag(u1.(*ir.UnaryExpr))
case ir.OPANIC:
return transformPanic(u1.(*ir.UnaryExpr))
case ir.OCLOSE, ir.ONEW, ir.OALIGNOF, ir.OOFFSETOF, ir.OSIZEOF:
case ir.OALIGNOF, ir.OOFFSETOF, ir.OSIZEOF:
// This corresponds to the EvalConst() call near end of typecheck().
return typecheck.EvalConst(u1)
case ir.OCLOSE, ir.ONEW:
// nothing more to do
return u1
}

View File

@ -81,7 +81,16 @@ func (g *irgen) validateBuiltin(name string, call *syntax.CallExpr) {
// Check that types2+gcSizes calculates sizes the same
// as cmd/compile does.
got, ok := constant.Int64Val(g.info.Types[call].Value)
tv := g.info.Types[call]
if !tv.IsValue() {
base.FatalfAt(g.pos(call), "expected a value")
}
if tv.Value == nil {
break // unsafe op is not a constant, so no further validation
}
got, ok := constant.Int64Val(tv.Value)
if !ok {
base.FatalfAt(g.pos(call), "expected int64 constant value")
}

View File

@ -881,7 +881,9 @@ func evalunsafe(n ir.Node) int64 {
case ir.OOFFSETOF:
// must be a selector.
n := n.(*ir.UnaryExpr)
if n.X.Op() != ir.OXDOT {
// ODOT and ODOTPTR are allowed in case the OXDOT transformation has
// already happened (e.g. during -G=3 stenciling).
if n.X.Op() != ir.OXDOT && n.X.Op() != ir.ODOT && n.X.Op() != ir.ODOTPTR {
base.Errorf("invalid expression %v", n)
return 0
}

View File

@ -0,0 +1,68 @@
// run -gcflags=-G=3
// Copyright 2021 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 (
"fmt"
"unsafe"
)
// size returns the size of type T
func size[T any](x T) uintptr {
return unsafe.Sizeof(x)
}
// size returns the alignment of type T
func align[T any](x T) uintptr {
return unsafe.Alignof(x)
}
type Tstruct[T any] struct {
f1 T
f2 int
}
// offset returns the offset of field f2 in the generic type Tstruct
func (r *Tstruct[T]) offset() uintptr {
return unsafe.Offsetof(r.f2)
}
func main() {
v1 := int(5)
if got, want := size(v1), unsafe.Sizeof(v1); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
if got, want := align(v1), unsafe.Alignof(v1); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
v2 := "abc"
if got, want := size(v2), unsafe.Sizeof(v2); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
if got, want := align(v2), unsafe.Alignof(v2); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
var v3 Tstruct[int]
if got, want := unsafe.Offsetof(v3.f2), unsafe.Sizeof(v1); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
var v4 Tstruct[interface{}]
var v5 interface{}
if got, want := unsafe.Offsetof(v4.f2), unsafe.Sizeof(v5); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
if got, want := v3.offset(), unsafe.Offsetof(v3.f2); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
if got, want := v4.offset(), unsafe.Offsetof(v4.f2); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
}