runtime: speed up ifaceeq for direct ifaces

name                    old time/op  new time/op  delta
EfaceCmpDiff-8           421ns ± 3%   299ns ± 3%  -28.93%  (p=0.000 n=92+94)
EfaceCmpDiffIndirect-8   497ns ± 4%   496ns ± 3%     ~     (p=0.840 n=98+92)

Change-Id: Id1a8c779413ba35ab0f58d055870b6a0714b51b7
Reviewed-on: https://go-review.googlesource.com/c/152163
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/src/runtime/alg.go b/src/runtime/alg.go
index 887dbebdeb..1c6795a1fa 100644
--- a/src/runtime/alg.go
+++ b/src/runtime/alg.go
@@ -224,7 +224,10 @@ func efaceeq(t *_type, x, y unsafe.Pointer) bool {
 		panic(errorString("comparing uncomparable type " + t.string()))
 	}
 	if isDirectIface(t) {
-		return eq(noescape(unsafe.Pointer(&x)), noescape(unsafe.Pointer(&y)))
+		// Direct interface types are ptr, chan, map, func, and single-element structs/arrays thereof.
+		// Maps and funcs are not comparable, so they can't reach here.
+		// Ptrs, chans, and single-element items can be compared directly using ==.
+		return x == y
 	}
 	return eq(x, y)
 }
@@ -238,7 +241,8 @@ func ifaceeq(tab *itab, x, y unsafe.Pointer) bool {
 		panic(errorString("comparing uncomparable type " + t.string()))
 	}
 	if isDirectIface(t) {
-		return eq(noescape(unsafe.Pointer(&x)), noescape(unsafe.Pointer(&y)))
+		// See comment in efaceeq.
+		return x == y
 	}
 	return eq(x, y)
 }