Revert "[dev.ssa] cmd/compile: don't Compile if Unimplemented"

This reverts commit 766bcc92.

Change-Id: I55413c1aa80d82c856a3ea89b4ffccf80fb58013
Reviewed-on: https://go-review.googlesource.com/12361Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -108,18 +108,17 @@ func buildssa(fn *Node) (ssafn *ssa.Func, usessa bool) {
 	// Link up variable uses to variable definitions
 	s.linkForwardReferences()
 
+	// Main call to ssa package to compile function
+	ssa.Compile(s.f)
+
 	// Calculate stats about what percentage of functions SSA handles.
 	if false {
-		defer func() { fmt.Printf("SSA implemented: %t\n", !e.unimplemented) }()
+		fmt.Printf("SSA implemented: %t\n", !e.unimplemented)
 	}
 
 	if e.unimplemented {
 		return nil, false
 	}
-
-	// Main call to ssa package to compile function.
-	ssa.Compile(s.f)
-
 	return s.f, usessa // TODO: return s.f, true once runtime support is in (gc maps, write barriers, etc.)
 }
 

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

@@ -8,7 +8,6 @@ import (
 	"bytes"
 	"fmt"
 	"io"
-	"os"
 )
 
 func printFunc(f *Func) {
@@ -69,22 +68,16 @@ func fprintFunc(w io.Writer, f *Func) {
 				n++
 			}
 			if m == n {
-				fmt.Fprintln(os.Stderr, "dependency cycle in block", b)
+				fmt.Fprintln(w, "dependency cycle!")
 				for _, v := range b.Values {
 					if printed[v.ID] {
 						continue
 					}
-					fmt.Fprintf(os.Stderr, "    %v\n", v.LongString())
+					fmt.Fprint(w, "    ")
+					fmt.Fprintln(w, v.LongString())
 					printed[v.ID] = true
 					n++
 				}
-				// Things are going to go very badly from here;
-				// one of the optimization passes is likely to hang.
-				// Frustratingly, panics here get swallowed by fmt,
-				// and just we end up here again if we call Fatalf.
-				// Use our last resort.
-				os.Exit(1)
-				return
 			}
 		}