Re: The (black?) art of inlining...

Jim Marshall <jim.marshall@xxxxxxxxxxxxxxxxx> · Mon, 25 Jun 2007 16:55:11 -0400

Daniel Lohmann wrote:

Jim Marshall schrieb:
I have some code which we have been compiling with GCC 3.2.2 (yes its 
old). We recently added Solaris SPARC which has GCC 3.4.6. I have a 
couple of functions that I would prefer to be inline all the time. On 
GCC 3.2.2 I receive no warnings when I compile my code (which makes me 
believe these functions are inlined). I am using the following compile 
options:

cc -o /home/jmars/server/lib/schema.o   -O3 -finline-functions 
-fmerge-constants -fexpensive-optimizations -Wuninitialized -fpic -c 
-Werror -Winline -Wformat -Wno-return-type 
-Werror-implicit-function-declaration -Wparentheses -Wredundant-decls 
-m32 -msse -minline-all-stringops -finline -D_UNICODE -DUNICODE 
-D_COMPILE_UNIX -D__USE_POSIX -D_GNU_SOURCE -DTHREAD_SAFE -D_REENTRANT 
-D_LINUX -I./include -DWSI_EXPAT_BUILD 
-I/home/jmars/server/private/include -I/home/jmars/api/include 
-I/home/jmars/utils/include -I/home/jmars/common/lib/include 
-I/home/jmars/202/wsi/thirdparty/expat/include -D_USE_GC 
./src/cimxml_schema.c

and I get the following warning (this is with GCC 4.1.1 on Linux FC 6) 
- (I don't have direct access to my Sparc machine but the warning was 
similar)

./src/schema.c: In function ‘scope_encodeformat’:
/home/jmars/server/api/include/apiext.h:382: warning: inlining failed 
in call to ‘freeValidMemory’: --param inline-unit-growth limit reached
./src/schema.c:3285: warning: called from here
make[2]: *** [/home/jmars/proto/temp/server/lib/schema.o] Error 1

The function is question is (in this case INLINE is defined as #define 
INLINE inline):

static INLINE void freeValidMemory(void* vptr, wsi_heap heap)
{
    if (vptr != NULL)
    {
        /* if we are finding leaks, make sure we always call GC_free */
        if (GC_find_leak == 0)
        {
            /* not looking for leaks */
            size_t ptrSize = GC_size(vptr);
            if (ptrSize > 0 && ptrSize <= GC_SMALL_SIZE)
            {
              /* set the first element to 0 (NULL) */
                memset(vptr, 0, 1);
            } else {
                GC_FREE(vptr);
            }
        } else {
            /* looking for leaks, call GC_FREE */
            GC_FREE(vptr);
        }
    }
}

Any thoughts on how I can force this function to be inline?

If you want a function to be inlined in any case define it with 
__attribute__((always_inline)).

Another option might be to generally increase the inline limit with 
-finline-limit=<high number>. The default is, AFAIK, 600, so giving it a 
6000 should inline almost everything. Take a look at the inline options 
in the gcc manual.

Daniel

Hi Daniel,
 Thanks for the reply. I was trying to avoid the -finline-limit usage. 
I tried the __attribute__((always_inline)) but this causes other 
warnings due to some of the other compiler flags I have. Specifically 
because I have the function declared in a header as static any module 
that includes this header but doesn't use these functions generate a 
warning "'freeValidMemory' defined but not used" :(

I think I will just stick with letting the compiler determine what it 
can inline and remove the -Winline, the compiler probably knows better 
then I do anyway :O

Thanks for the quick reply, I appreciate it!
-Jim