cmd/internal/obj/ppc64: fix assembly of SRADCC with immediate

sradi and sradi. hide the top bit of their immediate argument apart from the
rest of it, but the code only handled the sradi case.

I'm pretty sure this is the only instruction missing (a couple of the rotate
instructions encode their immediate the same way but their handling looks OK).

This fixes the failure of "GOARCH=amd64 ~/go/bin/go install -v runtime" as
reported in the bug.

Fixes #11987

Change-Id: I0cdefcd7a04e0e8fce45827e7054ffde9a83f589
Reviewed-on: https://go-review.googlesource.com/16710Reviewed-by: Minux Ma <minux@golang.org>

src/cmd/internal/obj/ppc64/asm9.go

@@ -2175,7 +2175,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 			r = int(p.To.Reg)
 		}
 		o1 = AOP_RRR(uint32(opirr(ctxt, int(p.As))), uint32(r), uint32(p.To.Reg), uint32(v)&31)
-		if p.As == ASRAD && (v&0x20 != 0) {
+		if (p.As == ASRAD || p.As == ASRADCC) && (v&0x20 != 0) {
 			o1 |= 1 << 1 /* mb[5] */
 		}
 

test/fixedbugs/issue11987.go

+// run
+
+// Copyright 2015 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.
+
+// Issue 11987. The ppc64 SRADCC instruction was misassembled in a way
+// lost bit 5 of the immediate so v>>32 was assembled as v>>0.  SRADCC
+// is only ever inserted by peep so it's hard to be sure when it will
+// be used. This formulation worked when the bug was fixed.
+
+package main
+
+import "fmt"
+
+var v int64 = 0x80000000
+
+func main() {
+	s := fmt.Sprintf("%v", v>>32 == 0)
+	if s != "true" {
+		fmt.Printf("BUG: v>>32 == 0 evaluated as %q\n", s)
+	}
+}