From af18bce87cc7ee1ffc68f91abefa241ab209539e Mon Sep 17 00:00:00 2001 From: Cherry Zhang Date: Sun, 20 Sep 2020 23:29:20 -0400 Subject: cmd/link: consider interface conversions only in reachable code The linker prunes methods that are not directly reachable if the receiver type is never converted to interface. Currently, this "never" is too strong: it is invalidated even if the interface conversion is in an unreachable function. This CL improves it by only considering interface conversions in reachable code. To do that, we introduce a marker relocation R_USEIFACE, which marks the target symbol as UsedInIface if the source symbol is reached. binary size before after cmd/compile 18897528 18887400 cmd/go 13607372 13470652 Change-Id: I66c6b69eeff9ae02d84d2e6f2bc7f1b29dd53910 Reviewed-on: https://go-review.googlesource.com/c/go/+/256797 Trust: Cherry Zhang Reviewed-by: Jeremy Faller Reviewed-by: Than McIntosh --- src/cmd/link/internal/ld/testdata/deadcode/ifacemethod.go | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'src/cmd/link/internal/ld/testdata/deadcode') diff --git a/src/cmd/link/internal/ld/testdata/deadcode/ifacemethod.go b/src/cmd/link/internal/ld/testdata/deadcode/ifacemethod.go index b62f18c342..32a24cf6f0 100644 --- a/src/cmd/link/internal/ld/testdata/deadcode/ifacemethod.go +++ b/src/cmd/link/internal/ld/testdata/deadcode/ifacemethod.go @@ -18,6 +18,13 @@ var p *T var e interface{} func main() { - p = new(T) // used T, but never converted to interface + p = new(T) // used T, but never converted to interface in any reachable code e.(I).M() // used I and I.M } + +func Unused() { // convert T to interface, but this function is not reachable + var i I = T(0) + i.M() +} + +var Unused2 interface{} = T(1) // convert T to interface, in an unreachable global initializer -- cgit v1.3