cmd/compile: avoid collisions between statictmps and user vars

Avoid name collisions between autogenerated statictmp variables and
user defined global variables.

Fixes #25113

Change-Id: I023eb42a5c2bd2f5352b046d33363faed87084dc
Reviewed-on: https://go-review.googlesource.com/c/142497Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -568,7 +568,7 @@ var statuniqgen int // name generator for static temps
 // returned node for readonly nodes.
 func staticname(t *types.Type) *Node {
 	// Don't use lookupN; it interns the resulting string, but these are all unique.
-	n := newname(lookup(fmt.Sprintf("statictmp_%d", statuniqgen)))
+	n := newname(lookup(fmt.Sprintf(".stmp_%d", statuniqgen)))
 	statuniqgen++
 	addvar(n, t, PEXTERN)
 	return n

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

@@ -439,7 +439,7 @@ func IsSanitizerSafeAddr(v *Value) bool {
 		// test sym.Type==objabi.SRODATA, but we don't
 		// initialize sym.Type until after function
 		// compilation.
-		if strings.HasPrefix(sym.Name, `"".statictmp_`) {
+		if strings.HasPrefix(sym.Name, `""..stmp_`) {
 			return true
 		}
 	}