Refactor permuted backtrace test allocation.

Refactor permuted backtrace test allocation that was originally used
only by the prof_accum test, so that it can be used by other heap
profiling test binaries.

test/include/test/btalloc.h

@@ -0,0 +1,31 @@
+/* btalloc() provides a mechanism for allocating via permuted backtraces. */
+void	*btalloc(size_t size, unsigned bits);
+
+#define	btalloc_n_proto(n)						\
+void	*btalloc_##n(size_t size, unsigned bits);
+btalloc_n_proto(0)
+btalloc_n_proto(1)
+
+#define	btalloc_n_gen(n)						\
+void *									\
+btalloc_##n(size_t size, unsigned bits)					\
+{									\
+	void *p;							\
+									\
+	if (bits == 0)							\
+		p = mallocx(size, 0);					\
+	else {								\
+		switch (bits & 0x1U) {					\
+		case 0:							\
+			p = (btalloc_0(size, bits >> 1));		\
+			break;						\
+		case 1:							\
+			p = (btalloc_1(size, bits >> 1));		\
+			break;						\
+		default: not_reached();					\
+		}							\
+	}								\
+	/* Intentionally sabotage tail call optimization. */		\
+	assert_ptr_not_null(p, "Unexpected mallocx() failure");		\
+	return (p);							\
+}

test/include/test/jemalloc_test.h.in

@@ -133,6 +133,7 @@
 /*
  * Common test utilities.
  */
+#include "test/btalloc.h"
 #include "test/math.h"
 #include "test/mtx.h"
 #include "test/mq.h"