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authorDenys Vlasenko2018-01-28 20:41:23 +0100
committerDenys Vlasenko2018-01-28 20:41:23 +0100
commit6f9442ff30f2fa7b66395935b0f59b01ecc89f0e (patch)
tree58fcee93b06a807e14a09811f4e04e9c095c8390 /shell
parentf19e3c1c6c96e3c709ac732ff70c586521f792d3 (diff)
downloadbusybox-6f9442ff30f2fa7b66395935b0f59b01ecc89f0e.zip
busybox-6f9442ff30f2fa7b66395935b0f59b01ecc89f0e.tar.gz
ash: make it possible to disable "const global ptr" optimization
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'shell')
-rw-r--r--shell/ash.c19
1 files changed, 16 insertions, 3 deletions
diff --git a/shell/ash.c b/shell/ash.c
index 6b7386f..4c1b5e4 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -263,6 +263,19 @@ typedef long arith_t;
# error "Do not even bother, ash will not run on NOMMU machine"
#endif
+/* We use a trick to have more optimized code (fewer pointer reloads):
+ * ash.c: extern struct globals *const ash_ptr_to_globals;
+ * ash_ptr_hack.c: struct globals *ash_ptr_to_globals;
+ * This way, compiler in ash.c knows the pointer can not change.
+ *
+ * However, this may break on weird arches or toolchains. In this case,
+ * set "-DBB_GLOBAL_CONST=''" in CONFIG_EXTRA_CFLAGS to disable
+ * this optimization.
+ */
+#ifndef BB_GLOBAL_CONST
+# define BB_GLOBAL_CONST const
+#endif
+
/* ============ Hash table sizes. Configurable. */
@@ -400,7 +413,7 @@ struct globals_misc {
#endif
pid_t backgndpid; /* pid of last background process */
};
-extern struct globals_misc *const ash_ptr_to_globals_misc;
+extern struct globals_misc *BB_GLOBAL_CONST ash_ptr_to_globals_misc;
#define G_misc (*ash_ptr_to_globals_misc)
#define exitstatus (G_misc.exitstatus )
#define back_exitstatus (G_misc.back_exitstatus )
@@ -1473,7 +1486,7 @@ struct globals_memstack {
size_t g_stacknleft; // = MINSIZE;
struct stack_block stackbase;
};
-extern struct globals_memstack *const ash_ptr_to_globals_memstack;
+extern struct globals_memstack *BB_GLOBAL_CONST ash_ptr_to_globals_memstack;
#define G_memstack (*ash_ptr_to_globals_memstack)
#define g_stackp (G_memstack.g_stackp )
#define g_stacknxt (G_memstack.g_stacknxt )
@@ -2062,7 +2075,7 @@ struct globals_var {
int lineno;
char linenovar[sizeof("LINENO=") + sizeof(int)*3];
};
-extern struct globals_var *const ash_ptr_to_globals_var;
+extern struct globals_var *BB_GLOBAL_CONST ash_ptr_to_globals_var;
#define G_var (*ash_ptr_to_globals_var)
#define shellparam (G_var.shellparam )
//#define redirlist (G_var.redirlist )