cmd/compile: skip runtime.nextFreeFast inlining test on MIPS64x

Since inlining budget calculation is fixed in CL 70151
runtime.nextFreeFast is no longer inlineable on MIPS64x because
it does not support Ctz64 as intrinsic. Skip the test.

Updates #22239.

Change-Id: Id00d55628ddb4b48d27aebfa10377a896765d569
Reviewed-on: https://go-review.googlesource.com/72271
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -135,11 +135,14 @@ func TestIntendedInlining(t *testing.T) {
 		},
 	}
 
-	if runtime.GOARCH != "386" {
+	if runtime.GOARCH != "386" && runtime.GOARCH != "mips64" && runtime.GOARCH != "mips64le" {
 		// nextFreeFast calls sys.Ctz64, which on 386 is implemented in asm and is not inlinable.
 		// We currently don't have midstack inlining so nextFreeFast is also not inlinable on 386.
-		// So check for it only on non-386 platforms.
+		// On MIPS64x, Ctz64 is not intrinsified and causes nextFreeFast too expensive to inline
+		// (Issue 22239).
 		want["runtime"] = append(want["runtime"], "nextFreeFast")
+	}
+	if runtime.GOARCH != "386" {
 		// As explained above, Ctz64 and Ctz32 are not Go code on 386.
 		// The same applies to Bswap32.
 		want["runtime/internal/sys"] = append(want["runtime/internal/sys"], "Ctz64")