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cmd/compile: make isfat handle 1-element array, 1-field struct
This will improve liveness analysis slightly, the same logic as isdirectiface curently does. In: type T struct { m map[int]int } v := T{} v.m = make(map[int]int) T is considered "fat", now it is not. So assigning to v.m is considered to clobber the entire v. This is follow up of CL 179057. Change-Id: Id6b4807b8e8521ef5d8bcb14fedb6dceb9dbf18c Reviewed-on: https://go-review.googlesource.com/c/go/+/179578 Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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@ -1453,9 +1453,21 @@ func liveness(e *ssafn, f *ssa.Func, pp *Progs) LivenessMap {
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func isfat(t *types.Type) bool {
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if t != nil {
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switch t.Etype {
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case TSTRUCT, TARRAY, TSLICE, TSTRING,
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case TSLICE, TSTRING,
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TINTER: // maybe remove later
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return true
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case TARRAY:
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// Array of 1 element, check if element is fat
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if t.NumElem() == 1 {
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return isfat(t.Elem())
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}
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return true
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case TSTRUCT:
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// Struct with 1 field, check if field is fat
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if t.NumFields() == 1 {
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return isfat(t.Field(0).Type)
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}
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return true
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}
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}
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@ -659,7 +659,7 @@ func bad40() {
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func good40() {
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ret := T40{} // ERROR "stack object ret T40$"
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ret.m = make(map[int]int) // ERROR "live at call to fastrand: .autotmp_[0-9]+ ret$" "stack object .autotmp_[0-9]+ map.hdr\[int\]int$"
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ret.m = make(map[int]int) // ERROR "live at call to fastrand: .autotmp_[0-9]+$" "stack object .autotmp_[0-9]+ map.hdr\[int\]int$"
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t := &ret
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printnl() // ERROR "live at call to printnl: ret$"
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// Note: ret is live at the printnl because the compiler moves &ret
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@ -27,14 +27,14 @@ func newT40() *T40 {
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}
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func bad40() {
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t := newT40() // ERROR "live at call to makemap: ret$" "stack object ret T40$" "stack object .autotmp_[0-9]+ map.hdr\[int\]int$"
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t := newT40() // ERROR "stack object ret T40$" "stack object .autotmp_[0-9]+ map.hdr\[int\]int$"
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printnl() // ERROR "live at call to printnl: ret$"
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useT40(t)
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}
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func good40() {
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ret := T40{} // ERROR "stack object ret T40$"
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ret.m = make(map[int]int, 42) // ERROR "live at call to makemap: ret$" "stack object .autotmp_[0-9]+ map.hdr\[int\]int$"
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ret.m = make(map[int]int, 42) // ERROR "stack object .autotmp_[0-9]+ map.hdr\[int\]int$"
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t := &ret
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printnl() // ERROR "live at call to printnl: ret$"
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useT40(t)
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