cmd/compile: don't accumulate duplicated named slots

Currently, in expand_calls, for each appearance of a named
variables's component, we add the named slot to f.Names list. If
a variable appears many times, we add it to f.Names many times.
Furthure, for each duplicated named slot, its entry in
f.NamedValues is a slice that contains all Values associated with
that name. This leads to quadratic behavior when iterating named
values like

	for _, name := range f.Names {
		for _, v := range f.NamedValues[name] {
			...
		}
	}

This CL makes it not to add duplicated entries to f.Names.

Change-Id: I82a8d009db81ecf48b4577e0bca501feff677cdf
Reviewed-on: https://go-review.googlesource.com/c/go/+/312093
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

diff --git a/src/cmd/compile/internal/ssa/expand_calls.go b/src/cmd/compile/internal/ssa/expand_calls.go
index 46c2388e7b8f085002bde5d196b24b3970a889ba..48e40bb00a3e887f10973e688bd3e4ed9f99df69 100644 (file)
--- a/src/cmd/compile/internal/ssa/expand_calls.go
+++ b/src/cmd/compile/internal/ssa/expand_calls.go
@@ -1378,9 +1378,11 @@ func expandCalls(f *Func) {
                // Leaf types may have debug locations
                if !x.isAlreadyExpandedAggregateType(v.Type) {
                        for _, l := range locs {
+                               if _, ok := f.NamedValues[l]; !ok {
+                                       f.Names = append(f.Names, l)
+                               }
                                f.NamedValues[l] = append(f.NamedValues[l], v)
                        }
-                       f.Names = append(f.Names, locs...)
                        continue
                }
                // Not-leaf types that had debug locations need to lose them.