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>
diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go
index 601e3c3..237a551 100644
--- a/src/cmd/compile/internal/gc/walk.go
+++ b/src/cmd/compile/internal/gc/walk.go
@@ -555,7 +555,7 @@
n.Left = walkexpr(n.Left, init)
n.Right = walkexpr(n.Right, init)
- case OSPTR, OITAB:
+ case OSPTR, OITAB, OIDATA:
n.Left = walkexpr(n.Left, init)
case OLEN, OCAP:
@@ -961,11 +961,13 @@
toKind := t.iet()
res := n.List.First()
+ scalar := !haspointers(res.Type)
// Avoid runtime calls in a few cases of the form _, ok := i.(T).
// This is faster and shorter and allows the corresponding assertX2X2
// routines to skip nil checks on their last argument.
- if isblank(res) {
+ // Also avoid runtime calls for converting interfaces to scalar concrete types.
+ if isblank(res) || (scalar && toKind == 'T') {
var fast *Node
switch toKind {
case 'T':
@@ -985,11 +987,27 @@
fast = Nod(ONE, nodnil(), tab)
}
if fast != nil {
- if Debug_typeassert > 0 {
- Warn("type assertion (ok only) inlined")
+ if isblank(res) {
+ if Debug_typeassert > 0 {
+ Warn("type assertion (ok only) inlined")
+ }
+ n = Nod(OAS, ok, fast)
+ n = typecheck(n, Etop)
+ } else {
+ if Debug_typeassert > 0 {
+ Warn("type assertion (scalar result) inlined")
+ }
+ n = Nod(OIF, ok, nil)
+ n.Likely = 1
+ if isblank(ok) {
+ n.Left = fast
+ } else {
+ n.Ninit.Set1(Nod(OAS, ok, fast))
+ }
+ n.Nbody.Set1(Nod(OAS, res, ifaceData(from, res.Type)))
+ n.Rlist.Set1(Nod(OAS, res, nil))
+ n = typecheck(n, Etop)
}
- n = Nod(OAS, ok, fast)
- n = typecheck(n, Etop)
break
}
}
