[dev.ssa] cmd/compile: with -N, don't put JMPs after calls

plive doesn't like the fact that we put JMPs right
after CALL ops to select{send,recv}.

Fixes SSA -N build.

Change-Id: I9b3c9e5293196094fd5a6206dd2f99784951f7a9
Reviewed-on: https://go-review.googlesource.com/19982
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/compile/internal/gc/ssa.go

@@ -3597,10 +3597,11 @@ func genssa(f *ssa.Func, ptxt *obj.Prog, gcargs, gclocals *Sym) {
 		}
 		// Emit control flow instructions for block
 		var next *ssa.Block
-		if i < len(f.Blocks)-1 && Debug['N'] == 0 {
+		if i < len(f.Blocks)-1 && (Debug['N'] == 0 || b.Kind == ssa.BlockCall) {
 			// If -N, leave next==nil so every block with successors
-			// ends in a JMP.  Helps keep line numbers for otherwise
-			// empty blocks.
+			// ends in a JMP (except call blocks - plive doesn't like
+			// select{send,recv} followed by a JMP call).  Helps keep
+			// line numbers for otherwise empty blocks.
 			next = f.Blocks[i+1]
 		}
 		x := Pc