runtime: use srcFunc for showframe
Since srcFunc can represent information for either an real text
function or an inlined function, this means we no longer have to
synthesize a fake _func just to call showframe on an inlined frame.
This is cleaner and also eliminates the one case where _func values
live in the heap. This will let us mark them NotInHeap, which will in
turn eliminate pesky write barriers in the traceback rewrite.
For #54466.
Change-Id: Ibf5e24d01ee4bf384c825e1a4e2922ef444a438e
Reviewed-on: https://go-review.googlesource.com/c/go/+/466097
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>