Use asm volatile during benchmarks.

configure.ac

@@ -546,6 +546,22 @@ typedef unsigned __int32 uint32_t;
     ;;
 esac
 AC_DEFINE_UNQUOTED([LG_VADDR], [$LG_VADDR], [ ])
+AC_CACHE_CHECK([asm volatile support],
+               [je_cv_asm_volatile],
+               AC_RUN_IFELSE([AC_LANG_PROGRAM(
+[[
+]],
+[[
+      void* ptr;
+      asm volatile("" : "+r"(ptr));
+      return 0;
+]])],
+[je_cv_asm_volatile=yes],
+[je_cv_asm_volatile=no],
+[je_cv_asm_volatile=no]))
+if test "x${je_cv_asm_volatile}" = "xyes"; then
+  AC_DEFINE([JEMALLOC_HAVE_ASM_VOLATILE], [ ], [ ])
+fi
 
 LD_PRELOAD_VAR="LD_PRELOAD"
 so="so"

include/jemalloc/internal/jemalloc_internal_defs.h.in

@@ -440,4 +440,7 @@
 /* If defined, realloc(ptr, 0) defaults to "free" instead of "alloc". */
 #undef JEMALLOC_ZERO_REALLOC_DEFAULT_FREE
 
+/* If defined, use volatile asm during benchmarks. */
+#undef JEMALLOC_HAVE_ASM_VOLATILE
+
 #endif /* JEMALLOC_INTERNAL_DEFS_H_ */

test/include/test/bench.h

@@ -58,3 +58,14 @@ compare_funcs(uint64_t nwarmup, uint64_t niter, const char *name_a,
 
 	dallocx(p, 0);
 }
+
+static inline void *
+no_opt_ptr(void *ptr) {
+#ifdef JEMALLOC_HAVE_ASM_VOLATILE
+  asm volatile("" : "+r"(ptr));
+#else
+  void *volatile dup = ptr;
+  ptr = dup;
+#endif
+  return ptr;
+}

test/stress/cpp/microbench.cpp

@@ -3,44 +3,50 @@
 
 static void
 malloc_free(void) {
-	void* volatile p = malloc(1);
+	void* p = malloc(1);
 	expect_ptr_not_null((void *)p, "Unexpected malloc failure");
+	p = no_opt_ptr(p);
 	free((void *)p);
 }
 
 static void
 new_delete(void) {
-	void* volatile p = ::operator new(1);
+	void* p = ::operator new(1);
 	expect_ptr_not_null((void *)p, "Unexpected new failure");
+	p = no_opt_ptr(p);
 	::operator delete((void *)p);
 }
 
 static void
 malloc_free_array(void) {
-	void* volatile p = malloc(sizeof(int)*8);
+	void* p = malloc(sizeof(int)*8);
 	expect_ptr_not_null((void *)p, "Unexpected malloc failure");
+	p = no_opt_ptr(p);
 	free((void *)p);
 }
 
 static void
 new_delete_array(void) {
-	int* volatile p = new int[8];
-	expect_ptr_not_null((int *)p, "Unexpected new[] failure");
+	int* p = new int[8];
+	expect_ptr_not_null((void *)p, "Unexpected new[] failure");
+	p = (int *)no_opt_ptr((void *)p);
 	delete[] (int *)p;
 }
 
 #if __cpp_sized_deallocation >= 201309
 static void
 new_sized_delete(void) {
-	void* volatile p = ::operator new(1);
+	void* p = ::operator new(1);
 	expect_ptr_not_null((void *)p, "Unexpected new failure");
+	p = no_opt_ptr(p);
 	::operator delete((void *)p, 1);
 }
 
 static void
 malloc_sdallocx(void) {
-	void* volatile p = malloc(1);
+	void* p = malloc(1);
 	expect_ptr_not_null((void *)p, "Unexpected malloc failure");
+	p = no_opt_ptr(p);
         sdallocx((void *)p, 1, 0);
 }
 #endif

test/stress/large_microbench.c

@@ -9,6 +9,7 @@ large_mallocx_free(void) {
 	 */
 	void *p = mallocx(SC_LARGE_MINCLASS, MALLOCX_TCACHE_NONE);
 	assert_ptr_not_null(p, "mallocx shouldn't fail");
+	p = no_opt_ptr(p);
 	free(p);
 }
 
@@ -16,6 +17,7 @@ static void
 small_mallocx_free(void) {
 	void *p = mallocx(16, 0);
 	assert_ptr_not_null(p, "mallocx shouldn't fail");
+	p = no_opt_ptr(p);
 	free(p);
 }
 

test/stress/microbench.c

@@ -9,6 +9,7 @@ malloc_free(void) {
 		test_fail("Unexpected malloc() failure");
 		return;
 	}
+	p = no_opt_ptr(p);
 	free(p);
 }
 
@@ -19,6 +20,7 @@ mallocx_free(void) {
 		test_fail("Unexpected mallocx() failure");
 		return;
 	}
+	p = no_opt_ptr(p);
 	free(p);
 }
 
@@ -35,6 +37,7 @@ malloc_dallocx(void) {
 		test_fail("Unexpected malloc() failure");
 		return;
 	}
+	p = no_opt_ptr(p);
 	dallocx(p, 0);
 }
 
@@ -45,6 +48,7 @@ malloc_sdallocx(void) {
 		test_fail("Unexpected malloc() failure");
 		return;
 	}
+	p = no_opt_ptr(p);
 	sdallocx(p, 1, 0);
 }
 
@@ -82,6 +86,7 @@ malloc_sallocx_free(void) {
 		test_fail("Unexpected malloc() failure");
 		return;
 	}
+	p = no_opt_ptr(p);
 	if (sallocx(p, 0) < 1) {
 		test_fail("Unexpected sallocx() failure");
 	}
@@ -103,6 +108,7 @@ malloc_nallocx_free(void) {
 		test_fail("Unexpected malloc() failure");
 		return;
 	}
+	p = no_opt_ptr(p);
 	if (nallocx(1, 0) < 1) {
 		test_fail("Unexpected nallocx() failure");
 	}