cmd/compile: generate makeslice calls with int arguments
Where possible generate calls to runtime makeslice with int arguments
during compile time instead of makeslice with int64 arguments.
This eliminates converting arguments for calls to makeslice with
int64 arguments for platforms where int64 values do not fit into
arguments of type int.
godoc 386 binary shrinks by approximately 12 kilobyte.
amd64:
name old time/op new time/op delta
MakeSlice-2 29.8ns ± 1% 29.8ns ± 1% ~ (p=1.000 n=24+24)
386:
name old time/op new time/op delta
MakeSlice-2 52.3ns ± 0% 45.9ns ± 0% -12.17% (p=0.000 n=25+22)
Fixes #15357
Change-Id: Icb8701bb63c5a83877d26c8a4b78e782ba76de7c
Reviewed-on: https://go-review.googlesource.com/27851
Run-TryBot: Martin Möhrmann <martisch@uos.de>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go
index 8173a2e..91895dd 100644
--- a/src/cmd/compile/internal/gc/walk.go
+++ b/src/cmd/compile/internal/gc/walk.go
@@ -1506,11 +1506,27 @@
r = walkexpr(r, init)
n = r
} else {
- // makeslice(et *Type, nel int64, max int64) (ary []any)
- fn := syslook("makeslice")
+ // n escapes; set up a call to makeslice.
+ // When len and cap can fit into int, use makeslice instead of
+ // makeslice64, which is faster and shorter on 32 bit platforms.
+ len, cap := l, r
+
+ fnname := "makeslice64"
+ argtype := Types[TINT64]
+
+ // typechecking guarantees that TIDEAL len/cap are positive and fit in an int.
+ // The case of len or cap overflow when converting TUINT or TUINTPTR to TINT
+ // will be handled by the negative range checks in makeslice during runtime.
+ if (len.Type.IsKind(TIDEAL) || Maxintval[len.Type.Etype].Cmp(Maxintval[TUINT]) <= 0) &&
+ (cap.Type.IsKind(TIDEAL) || Maxintval[cap.Type.Etype].Cmp(Maxintval[TUINT]) <= 0) {
+ fnname = "makeslice"
+ argtype = Types[TINT]
+ }
+
+ fn := syslook(fnname)
fn = substArgTypes(fn, t.Elem()) // any-1
- n = mkcall1(fn, n.Type, init, typename(t.Elem()), conv(l, Types[TINT64]), conv(r, Types[TINT64]))
+ n = mkcall1(fn, t, init, typename(t.Elem()), conv(len, argtype), conv(cap, argtype))
}
case ORUNESTR:
