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From: "peteraward+gcc at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/51506] New: Function cloning misses constant struct Date: Sun, 11 Dec 2011 23:58:00 -0000 [thread overview] Message-ID: <bug-51506-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51506 Bug #: 51506 Summary: Function cloning misses constant struct Classification: Unclassified Product: gcc Version: 4.6.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization AssignedTo: unassigned@gcc.gnu.org ReportedBy: peteraward+gcc@gmail.com The actual problem I’m dealing with is with avr-gcc, so the goal is to achieve a small code size. I’m trying to write my code like this: lcd_init(lcd_t l, ...) where the first parameter is passed a *constant* struct which contains the memory addresses of each of the pins for the LCD. Thus, I want the compiler to note that all calls have the same first argument, clone the function, and propagate the constant. However, it doesn’t seem to be working in practice. In trying to build this test case, I found the compiler would just inline all the functions, which defeats the point (in the actual code, the cost of inlining is too high). So, I’ve added the noinline attribute, which I don’t think should stop this optimisation, but apologies if it does. Anyhow, here’s the testcase. (using gcc version 4.6.2 (Debian 4.6.2-5), on 64-bit Linux) $ cat test.c typedef struct { int a; int b; } dint; __attribute__((noinline)) static int compute_int(int x, int var) { int y = 0; for (int i = 0; i < x; i++) y += i * x; return y + var; } __attribute__((noinline)) static int compute_dint(dint x, int var) { int z = x.a + x.b; int y = 0; for (int i = 0; i < z; i++) y += i * z; return y + var; } int main() { int rv; rv += compute_dint((dint) {6, 1}, 1); rv += compute_dint((dint) {6, 1}, 2); rv += compute_dint((dint) {6, 1}, 3); rv += compute_int(5, 1); rv += compute_int(5, 2); rv += compute_int(5, 3); return rv; } $ gcc -fdump-ipa-all -fipa-cp -fipa-cp-clone -Os -std=c99 test.c Expected result: both compute_int and compute_dint should be optimised to versions where "x" is constant. Actual reslut: only compute_int is optimised.
next reply other threads:[~2011-12-11 23:41 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-12-11 23:58 peteraward+gcc at gmail dot com [this message] 2011-12-12 10:04 ` [Bug tree-optimization/51506] " rguenth at gcc dot gnu.org 2011-12-13 2:21 ` pinskia at gcc dot gnu.org 2021-07-19 3:06 ` [Bug ipa/51506] Function cloning misses constant struct at -Os vs -O2 pinskia at gcc dot gnu.org
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