cmd/gc: faster code, mainly for rotate
* Eliminate bounds check on known small shifts.
* Rewrite x<<s | x>>(32-s) as a rotate (constant s).
* More aggressive (but still minimal) range analysis.
R=ken, dave, iant
CC=golang-dev
https://golang.org/cl/6209077
diff --git a/test/rotate.go b/test/rotate.go
new file mode 100644
index 0000000..67d32d7
--- /dev/null
+++ b/test/rotate.go
@@ -0,0 +1,141 @@
+// $G $D/$F.go && $L $F.$A &&
+// ./$A.out >tmp.go && $G tmp.go && $L -o $A.out1 tmp.$A && ./$A.out1
+// rm -f tmp.go $A.out1
+
+// Copyright 2012 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.
+
+// Generate test of shift and rotate by constants.
+// The output is compiled and run.
+//
+// The output takes around a minute to compile, link, and run
+// but it is only done during ./run, not in normal builds using run.go.
+
+package main
+
+import (
+ "bufio"
+ "flag"
+ "fmt"
+ "os"
+)
+
+func main() {
+ flag.Parse()
+
+ b := bufio.NewWriter(os.Stdout)
+ defer b.Flush()
+
+ fmt.Fprintf(b, "%s\n", prolog)
+
+ for logBits := uint(3); logBits <= 6; logBits++ {
+ for mode := 0; mode < 1<<2; mode++ {
+ gentest(b, 1<<logBits, mode&1 != 0, mode&2 != 0)
+ }
+ }
+}
+
+const prolog = `
+
+package main
+
+import (
+ "fmt"
+ "os"
+)
+
+var (
+ i8 int8 = 0x12
+ i16 int16 = 0x1234
+ i32 int32 = 0x12345678
+ i64 int64 = 0x123456789abcdef0
+ ui8 uint8 = 0x12
+ ui16 uint16 = 0x1234
+ ui32 uint32 = 0x12345678
+ ui64 uint64 = 0x123456789abcdef0
+
+ ni8 = ^i8
+ ni16 = ^i16
+ ni32 = ^i32
+ ni64 = ^i64
+ nui8 = ^ui8
+ nui16 = ^ui16
+ nui32 = ^ui32
+ nui64 = ^ui64
+)
+
+var nfail = 0
+
+func check(desc string, have, want interface{}) {
+ if have != want {
+ nfail++
+ fmt.Printf("%s = %T(%#x), want %T(%#x)\n", desc, have, have, want, want)
+ if nfail >= 100 {
+ fmt.Printf("BUG: stopping after 100 failures\n")
+ os.Exit(0)
+ }
+ }
+}
+
+func main() {
+ if nfail > 0 {
+ fmt.Printf("BUG\n")
+ }
+}
+
+`
+
+func gentest(b *bufio.Writer, bits uint, unsigned, inverted bool) {
+ fmt.Fprintf(b, "func init() {\n")
+ defer fmt.Fprintf(b, "}\n")
+ n := 0
+
+ // Generate tests for left/right and right/left.
+ for l := uint(0); l <= bits; l++ {
+ for r := uint(0); r <= bits; r++ {
+ typ := fmt.Sprintf("int%d", bits)
+ v := fmt.Sprintf("i%d", bits)
+ if unsigned {
+ typ = "u" + typ
+ v = "u" + v
+ }
+ v0 := int64(0x123456789abcdef0)
+ if inverted {
+ v = "n" + v
+ v0 = ^v0
+ }
+ expr1 := fmt.Sprintf("%s<<%d | %s>>%d", v, l, v, r)
+ expr2 := fmt.Sprintf("%s>>%d | %s<<%d", v, r, v, l)
+
+ var result string
+ if unsigned {
+ v := uint64(v0) >> (64 - bits)
+ v = v<<l | v>>r
+ v <<= 64 - bits
+ v >>= 64 - bits
+ result = fmt.Sprintf("%#x", v)
+ } else {
+ v := int64(v0) >> (64 - bits)
+ v = v<<l | v>>r
+ v <<= 64 - bits
+ v >>= 64 - bits
+ result = fmt.Sprintf("%#x", v)
+ }
+
+ fmt.Fprintf(b, "\tcheck(%q, %s, %s(%s))\n", expr1, expr1, typ, result)
+ fmt.Fprintf(b, "\tcheck(%q, %s, %s(%s))\n", expr2, expr2, typ, result)
+
+ // Chop test into multiple functions so that there's not one
+ // enormous function to compile/link.
+ // All the functions are named init so we don't have to do
+ // anything special to call them. ☺
+ if n++; n >= 100 {
+ fmt.Fprintf(b, "}\n")
+ fmt.Fprintf(b, "func init() {\n")
+ n = 0
+ }
+ }
+ }
+}
+
