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cmd/compile: better documentation around checkwidth 

Change-Id: I5c7ec9676b5573c883c196459acea85aa9ff8130
Reviewed-on: https://go-review.googlesource.com/c/146021
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Robert Griesemer 2018-10-29 13:44:44 -07:00
parent 84b96c21bf
commit fde4b9ed14
2 changed files with 14 additions and 14 deletions
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16
src/cmd/compile/internal/gc/align.go
View File

@ -208,7 +208,7 @@ func dowidth(t *types.Type) {
}
t.Width = -2
t.Align = 0
t.Align = 0 // 0 means use t.Width, below
et := t.Etype
switch et {
@ -222,7 +222,7 @@ func dowidth(t *types.Type) {
}
}
w := int64(0)
var w int64
switch et {
default:
Fatalf("dowidth: unknown type: %v", t)
@ -366,7 +366,7 @@ func dowidth(t *types.Type) {
t.Width = w
if t.Align == 0 {
if w > 8 || w&(w-1) != 0 || w == 0 {
if w == 0 || w > 8 || w&(w-1) != 0 {
Fatalf("invalid alignment for %v", t)
}
t.Align = uint8(w)
@ -423,12 +423,11 @@ func checkwidth(t *types.Type) {
return
}
if t.Deferwidth() {
return
// if type has not yet been pushed on deferredTypeStack yet, do it now
if !t.Deferwidth() {
t.SetDeferwidth(true)
deferredTypeStack = append(deferredTypeStack, t)
}
t.SetDeferwidth(true)
deferredTypeStack = append(deferredTypeStack, t)
}
func defercheckwidth() {
@ -443,6 +442,7 @@ func resumecheckwidth() {
if defercalc == 0 {
Fatalf("resumecheckwidth")
}
for len(deferredTypeStack) > 0 {
t := deferredTypeStack[len(deferredTypeStack)-1]
deferredTypeStack = deferredTypeStack[:len(deferredTypeStack)-1]

12
src/cmd/compile/internal/types/type.go
View File

@ -141,7 +141,7 @@ type Type struct {
Extra interface{}
// Width is the width of this Type in bytes.
Width int64
Width int64 // valid if Align > 0
methods Fields
allMethods Fields
@ -156,16 +156,16 @@ type Type struct {
Vargen int32 // unique name for OTYPE/ONAME
Etype EType // kind of type
Align uint8 // the required alignment of this type, in bytes
Align uint8 // the required alignment of this type, in bytes (0 means Width and Align have not yet been computed)
flags bitset8
}
const (
typeNotInHeap = 1 << iota // type cannot be heap allocated
typeBroke // broken type definition
typeNoalg // suppress hash and eq algorithm generation
typeDeferwidth
typeNotInHeap = 1 << iota // type cannot be heap allocated
typeBroke // broken type definition
typeNoalg // suppress hash and eq algorithm generation
typeDeferwidth // width computation has been deferred and type is on deferredTypeStack
typeRecur
)