cmd/compile: use staticuint64s instead of staticbytes

There are still two places in src/runtime/string.go that use
staticbytes, so we cannot delete it just yet.

There is a new codegen test to verify that the index calculation
is constant-folded, at least on amd64. ppc64, mips[64] and s390x
cannot currently do that.

There is also a new runtime benchmark to ensure that this does not
slow down performance (tested against parent commit):

name                      old time/op  new time/op  delta
ConvT2EByteSized/bool-4   1.07ns ± 1%  1.07ns ± 1%   ~     (p=0.060 n=14+15)
ConvT2EByteSized/uint8-4  1.06ns ± 1%  1.07ns ± 1%   ~     (p=0.095 n=14+15)

Updates #37612

Change-Id: I5ec30738edaa48cda78dfab4a78e24a32fa7fd6a
Reviewed-on: https://go-review.googlesource.com/c/go/+/221957
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/test/codegen/smallintiface.go b/test/codegen/smallintiface.go
new file mode 100644
index 0000000000..0207a0af79
--- /dev/null
+++ b/test/codegen/smallintiface.go
@@ -0,0 +1,22 @@
+// asmcheck
+
+package codegen
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+func booliface() interface{} {
+	// amd64:`LEAQ\truntime.staticuint64s\+8\(SB\)`
+	return true
+}
+
+func smallint8iface() interface{} {
+	// amd64:`LEAQ\truntime.staticuint64s\+2024\(SB\)`
+	return int8(-3)
+}
+
+func smalluint8iface() interface{} {
+	// amd64:`LEAQ\truntime.staticuint64s\+24\(SB\)`
+	return uint8(3)
+}