cmd/compile: inline x, ok := y.(T) where T is a scalar

When T is a scalar, there are no runtime calls
required, which makes this a clear win.

encoding/binary:
WriteInts-8                958ns ± 3%     864ns ± 2%   -9.80%  (p=0.000 n=15+15)

This also considerably shrinks a core fmt
routine:

Before: "".(*pp).printArg t=1 size=3952 args=0x20 locals=0xf0
After:  "".(*pp).printArg t=1 size=2624 args=0x20 locals=0x98

Unfortunately, I find it very hard to get stable
numbers out of the fmt benchmarks due to thermal scaling.

Change-Id: I1278006b030253bf8e48dc7631d18985cdaa143d
Reviewed-on: https://go-review.googlesource.com/26659
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>

1 files changed, 15 insertions, 1 deletions

diff --git a/test/interface/assertinline.go b/test/interface/assertinline.go
index 227fe70d87..c3f3624570 100644
--- a/test/interface/assertinline.go
+++ b/test/interface/assertinline.go
@@ -43,7 +43,7 @@ func assertbig(x interface{}) complex128 {
 }
 
 func assertbig2(x interface{}) (complex128, bool) {
-	z, ok := x.(complex128) // ERROR "type assertion not inlined"
+	z, ok := x.(complex128) // ERROR "type assertion .scalar result. inlined"
 	return z, ok
 }
 
@@ -51,3 +51,17 @@ func assertbig2ok(x interface{}) (complex128, bool) {
 	_, ok := x.(complex128) // ERROR "type assertion [(]ok only[)] inlined"
 	return 0, ok
 }
+
+func assertslice(x interface{}) []int {
+	return x.([]int) // ERROR "type assertion not inlined"
+}
+
+func assertslice2(x interface{}) ([]int, bool) {
+	z, ok := x.([]int) // ERROR "type assertion not inlined"
+	return z, ok
+}
+
+func assertslice2ok(x interface{}) ([]int, bool) {
+	_, ok := x.([]int) // ERROR "type assertion [(]ok only[)] inlined"
+	return nil, ok
+}