runtime: avoid repeated findmoduledatap calls

Currently almost every function that deals with a *_func has to first
look up the *moduledata for the module containing the function's entry
point. This means we almost always do at least two identical module
lookups whenever we deal with a *_func (one to get the *_func and
another to get something from its module data) and sometimes several
more.

Fix this by making findfunc return a new funcInfo type that embeds
*_func, but also includes the *moduledata, and making all of the
functions that currently take a *_func instead take a funcInfo and use
the already-found *moduledata.

This transformation is trivial for the most part, since the *_func
type is usually inferred. The annoying part is that we can no longer
use nil to indicate failure, so this introduces a funcInfo.valid()
method and replaces nil checks with calls to valid.

Change-Id: I9b8075ef1c31185c1943596d96dec45c7ab5100f
Reviewed-on: https://go-review.googlesource.com/37331
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/runtime/signal_linux_s390x.go b/src/runtime/signal_linux_s390x.go
index de71ee950d..a31f436411 100644
--- a/src/runtime/signal_linux_s390x.go
+++ b/src/runtime/signal_linux_s390x.go
@@ -103,7 +103,7 @@ func (c *sigctxt) preparePanic(sig uint32, gp *g) {
 	// but we do recognize the link register as code,
 	// then assume this was a call to non-code and treat like
 	// pc == 0, to make unwinding show the context.
-	if pc != 0 && findfunc(pc) == nil && findfunc(uintptr(c.link())) != nil {
+	if pc != 0 && !findfunc(pc).valid() && findfunc(uintptr(c.link())).valid() {
 		pc = 0
 	}