From af7169b4a70eb3f60555ced17a40780f70aaaa5c Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Fri, 25 Oct 2019 12:12:22 +0200 Subject: [PATCH] clang/llvm 9 fix - do not eliminate a store to a fake "const" This is *much* better (9 kbytes better) than dropping "*const" optimization trick. Signed-off-by: Denys Vlasenko --- coreutils/test.c | 2 +- include/libbb.h | 22 +++++++++++++++++++++- libbb/appletlib.c | 2 +- libbb/lineedit.c | 2 +- shell/ash.c | 6 +++--- 5 files changed, 27 insertions(+), 7 deletions(-) diff --git a/coreutils/test.c b/coreutils/test.c index 868ffbecb..a08986130 100644 --- a/coreutils/test.c +++ b/coreutils/test.c @@ -411,7 +411,7 @@ extern struct test_statics *const test_ptr_to_statics; #define leaving (S.leaving ) #define INIT_S() do { \ - (*(struct test_statics**)&test_ptr_to_statics) = xzalloc(sizeof(S)); \ + (*(struct test_statics**)not_const_pp(&test_ptr_to_statics)) = xzalloc(sizeof(S)); \ barrier(); \ } while (0) #define DEINIT_S() do { \ diff --git a/include/libbb.h b/include/libbb.h index 111d1b790..05a560977 100644 --- a/include/libbb.h +++ b/include/libbb.h @@ -2153,12 +2153,32 @@ struct globals; * Magic prevents ptr_to_globals from going into rodata. * If you want to assign a value, use SET_PTR_TO_GLOBALS(x) */ extern struct globals *const ptr_to_globals; + +#if defined(__clang_major__) && __clang_major__ >= 9 +/* Clang/llvm drops assignment to "constant" storage. Silently. + * Needs serious convincing to not eliminate the store. + */ +static ALWAYS_INLINE void* not_const_pp(const void *p) +{ + void *pp; + __asm__ __volatile__( + "# forget that p points to const" + : /*outputs*/ "=r" (pp) + : /*inputs*/ "0" (p) + ); + return pp; +} +#else +static ALWAYS_INLINE void* not_const_pp(const void *p) { return (void*)p; } +#endif + /* At least gcc 3.4.6 on mipsel system needs optimization barrier */ #define barrier() __asm__ __volatile__("":::"memory") #define SET_PTR_TO_GLOBALS(x) do { \ - (*(struct globals**)&ptr_to_globals) = (void*)(x); \ + (*(struct globals**)not_const_pp(&ptr_to_globals)) = (void*)(x); \ barrier(); \ } while (0) + #define FREE_PTR_TO_GLOBALS() do { \ if (ENABLE_FEATURE_CLEAN_UP) { \ free(ptr_to_globals); \ diff --git a/libbb/appletlib.c b/libbb/appletlib.c index 9fa17cfa1..f842e73cc 100644 --- a/libbb/appletlib.c +++ b/libbb/appletlib.c @@ -304,7 +304,7 @@ void lbb_prepare(const char *applet IF_FEATURE_INDIVIDUAL(, char **argv)) { #ifdef __GLIBC__ - (*(int **)&bb_errno) = __errno_location(); + (*(int **)not_const_pp(&bb_errno)) = __errno_location(); barrier(); #endif applet_name = applet; diff --git a/libbb/lineedit.c b/libbb/lineedit.c index fbabc6c12..b1ec52b88 100644 --- a/libbb/lineedit.c +++ b/libbb/lineedit.c @@ -203,7 +203,7 @@ extern struct lineedit_statics *const lineedit_ptr_to_statics; #define delbuf (S.delbuf ) #define INIT_S() do { \ - (*(struct lineedit_statics**)&lineedit_ptr_to_statics) = xzalloc(sizeof(S)); \ + (*(struct lineedit_statics**)not_const_pp(&lineedit_ptr_to_statics)) = xzalloc(sizeof(S)); \ barrier(); \ cmdedit_termw = 80; \ IF_USERNAME_OR_HOMEDIR(home_pwd_buf = (char*)null_str;) \ diff --git a/shell/ash.c b/shell/ash.c index c5588ea66..4b5eafa7c 100644 --- a/shell/ash.c +++ b/shell/ash.c @@ -489,7 +489,7 @@ extern struct globals_misc *BB_GLOBAL_CONST ash_ptr_to_globals_misc; #define random_gen (G_misc.random_gen ) #define backgndpid (G_misc.backgndpid ) #define INIT_G_misc() do { \ - (*(struct globals_misc**)&ash_ptr_to_globals_misc) = xzalloc(sizeof(G_misc)); \ + (*(struct globals_misc**)not_const_pp(&ash_ptr_to_globals_misc)) = xzalloc(sizeof(G_misc)); \ barrier(); \ curdir = nullstr; \ physdir = nullstr; \ @@ -1542,7 +1542,7 @@ extern struct globals_memstack *BB_GLOBAL_CONST ash_ptr_to_globals_memstack; #define g_stacknleft (G_memstack.g_stacknleft) #define stackbase (G_memstack.stackbase ) #define INIT_G_memstack() do { \ - (*(struct globals_memstack**)&ash_ptr_to_globals_memstack) = xzalloc(sizeof(G_memstack)); \ + (*(struct globals_memstack**)not_const_pp(&ash_ptr_to_globals_memstack)) = xzalloc(sizeof(G_memstack)); \ barrier(); \ g_stackp = &stackbase; \ g_stacknxt = stackbase.space; \ @@ -2165,7 +2165,7 @@ extern struct globals_var *BB_GLOBAL_CONST ash_ptr_to_globals_var; #endif #define INIT_G_var() do { \ unsigned i; \ - (*(struct globals_var**)&ash_ptr_to_globals_var) = xzalloc(sizeof(G_var)); \ + (*(struct globals_var**)not_const_pp(&ash_ptr_to_globals_var)) = xzalloc(sizeof(G_var)); \ barrier(); \ for (i = 0; i < ARRAY_SIZE(varinit_data); i++) { \ varinit[i].flags = varinit_data[i].flags; \