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cmd/compile: generalize isfat to handle 1-field structs and 1-element arrays

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After CL 192979, it is safe now to optimize isfat slightly to handle
1-field structs and 1-element arrays.

Change-Id: Ie3bc30299abbcef36eee7a0681997cc2f88ed6a3
Reviewed-on: https://go-review.googlesource.com/c/go/+/192980
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
Cuong Manh Le 2019-09-04 11:11:22 +07:00 committed by Matthew Dempsky
parent 55c0ad4b62
commit 3f0437e175
1 changed files with 15 additions and 2 deletions
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17
src/cmd/compile/internal/gc/plive.go
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@ -304,7 +304,7 @@ func (lv *Liveness) valueEffects(v *ssa.Value) (int32, liveEffect) {
var effect liveEffect var effect liveEffect
// Read is a read, obviously. // Read is a read, obviously.
// //
// Addr is a read also, as any subseqent holder of the pointer must be able // Addr is a read also, as any subsequent holder of the pointer must be able
// to see all the values (including initialization) written so far. // to see all the values (including initialization) written so far.
// This also prevents a variable from "coming back from the dead" and presenting // This also prevents a variable from "coming back from the dead" and presenting
// stale pointers to the garbage collector. See issue 28445. // stale pointers to the garbage collector. See issue 28445.
@ -1450,12 +1450,25 @@ func liveness(e *ssafn, f *ssa.Func, pp *Progs) LivenessMap {
return lv.livenessMap return lv.livenessMap
} }
// TODO(cuonglm,mdempsky): Revisit after #24416 is fixed.
func isfat(t *types.Type) bool { func isfat(t *types.Type) bool {
if t != nil { if t != nil {
switch t.Etype { switch t.Etype {
case TSTRUCT, TARRAY, TSLICE, TSTRING, case TSLICE, TSTRING,
TINTER: // maybe remove later TINTER: // maybe remove later
return true return true
case TARRAY:
// Array of 1 element, check if element is fat
if t.NumElem() == 1 {
return isfat(t.Elem())
}
return true
case TSTRUCT:
// Struct with 1 field, check if field is fat
if t.NumFields() == 1 {
return isfat(t.Field(0).Type)
}
return true
} }
} }