[dev.ssa] cmd/compile: minor cleanup

Change-Id: Ib33f3b1cfa09f410675d275e214d8ddc246c53c3
Reviewed-on: https://go-review.googlesource.com/12548Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -22,6 +22,7 @@ func buildssa(fn *Node) (ssafn *ssa.Func, usessa bool) {
 	usessa = strings.HasSuffix(name, "_ssa")
 
 	if usessa {
+		fmt.Println("generating SSA for", name)
 		dumplist("buildssa-enter", fn.Func.Enter)
 		dumplist("buildssa-body", fn.Nbody)
 	}
@@ -481,16 +482,14 @@ func (s *state) stmt(n *Node) {
 
 		s.startBlock(bThen)
 		s.stmtList(n.Nbody)
-		b = s.endBlock()
-		if b != nil {
+		if b := s.endBlock(); b != nil {
 			addEdge(b, bEnd)
 		}
 
 		if n.Rlist != nil {
 			s.startBlock(bElse)
 			s.stmtList(n.Rlist)
-			b = s.endBlock()
-			if b != nil {
+			if b := s.endBlock(); b != nil {
 				addEdge(b, bEnd)
 			}
 		}

src/cmd/compile/internal/ssa/TODO

@@ -27,6 +27,7 @@ Regalloc
  - Handle 2-address instructions.
  - Floating point registers
  - Make calls clobber all registers
+ - Make liveness analysis non-quadratic.
 
 StackAlloc:
  - Sort variables so all ptr-containing ones are first (so stack
@@ -60,3 +61,5 @@ Other
    expression subtrees in the output.
  - Implement memory zeroing with REPSTOSQ and DuffZero
  - make deadstore work with zeroing.
+ - Add a value range propagation optimization pass.
+   Use it for bounds check elimination and bitwidth reduction.