[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 qinzhao at gcc dot gnu.org changed: What|Removed |Added Status|ASSIGNED|RESOLVED

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #47 from qinzhao at gcc dot gnu.org --- all the issues triggered by the previous patch have been fixed. I am planing to close this PR as fixed.

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #46 from qinzhao at gcc dot gnu.org --- https://gcc.gnu.org/viewcvs/gcc?view=revision=263028 was to fix the optimization level issue.

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 Jakub Jelinek changed: What|Removed |Added Target Milestone|8.2 |8.3 --- Comment #45 from Jakub Jelinek

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #44 from Qing Zhao --- > (In reply to wilco from comment #43) will provide a simple patch for this issue.

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #43 from Wilco --- (In reply to qinzhao from comment #42) > just checked in the patch for fixing the unsigned char issue as: > https://gcc.gnu.org/viewcvs/gcc?view=revision=262907 That looks it is using unsigned char accesses

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #42 from qinzhao at gcc dot gnu.org --- just checked in the patch for fixing the unsigned char issue as: https://gcc.gnu.org/viewcvs/gcc?view=revision=262907

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #41 from Qing Zhao --- > --- Comment #40 from Wilco --- > See eg. http://www.iso-9899.info/n1570.html section 7.24.4: > > "The sign of a nonzero value returned by the comparison functions memcmp, > strcmp, and strncmp is determined

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #40 from Wilco --- (In reply to Qing Zhao from comment #39) > > --- Comment #38 from Wilco --- > > This uses signed char while the C standard says the comparison is done on > > unsigned chars. > > > > during my implementation, I

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #39 from Qing Zhao --- > --- Comment #38 from Wilco --- > This uses signed char while the C standard says the comparison is done on > unsigned chars. > during my implementation, I did some research on whether I should use

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #38 from Wilco --- (In reply to qinzhao from comment #37) > since all the implementation were in trunk. > can I close this PR now? Thanks, it generates pretty much what I expected for t1. However there is an issue: t1:

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #37 from qinzhao at gcc dot gnu.org --- since all the implementation were in trunk. can I close this PR now?

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #36 from qinzhao at gcc dot gnu.org --- the 3rd part (the last part) of this PR was checked into GCC 9 today as: https://gcc.gnu.org/viewcvs/gcc?view=revision=262636

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 qinzhao at gcc dot gnu.org changed: What|Removed |Added CC||qinzhao at gcc dot gnu.org

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 Jakub Jelinek changed: What|Removed |Added Target Milestone|8.0 |8.2 --- Comment #34 from Jakub Jelinek

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #33 from Qing Zhao --- with SPEC2017 on X86, I didn't see any run-time performance change as expected. due to the date I collected for code size change, looks like that n=3 or n=4 might be a reasonable default. n=3 might be safer.

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #32 from Qing Zhao --- Created attachment 43298 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43298=edit code size impact from inlining str(n)cmp with different n on X86

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #31 from Wilco --- (In reply to Qing Zhao from comment #30) > (in reply to Wilco from comment #29) > > > > The new test is better, however it uses i % 15 which means an expensive > > division by constant every loop iteration. It's

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #30 from Qing Zhao --- (in reply to Wilco from comment #29) > > The new test is better, however it uses i % 15 which means an expensive > division by constant every loop iteration. It's best to change to i & 15. Also > using an

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #29 from Wilco --- (In reply to Qing Zhao from comment #28) > > > > I don't think this is a good test. Repeatedly calling strcmp with the same > > inputs is not something real code does, especially when the string matches > >

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #28 from Qing Zhao --- > > I don't think this is a good test. Repeatedly calling strcmp with the same > inputs is not something real code does, especially when the string matches > exactly. Why would it do that? The consequence

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #27 from Richard Earnshaw --- (In reply to Qing Zhao from comment #23) > qinzhao@gcc116:~/Bugs/78809/const_cmp$ cat t_p.c > #include > > char array[]= "fishi"; > > #define NUM 10 > int

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 Qing Zhao changed: What|Removed |Added Attachment #42449|0 |1 is obsolete|

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #25 from Wilco --- (In reply to Qing Zhao from comment #24) > From the above, we can see: > even with n is as big as 20, inlined version is much faster than the > non-inlined version, both on aarch64 (no hardware string compare

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #24 from Qing Zhao --- From the above, we can see: even with n is as big as 20, inlined version is much faster than the non-inlined version, both on aarch64 (no hardware string compare insn provided) and X86 (hardware string

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #23 from Qing Zhao --- I have an implementation for the part C of this task in my private space: part C: for strcmp (s1, s2), strncmp (s1, s2, n): if the result is NOT used to do simple equality test against zero, one of

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #22 from Qing Zhao --- https://gcc.gnu.org/ml/gcc-patches/2017-12/msg00962.html 2nd patch

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #21 from Jeffrey A. Law --- Author: law Date: Fri Nov 17 05:32:05 2017 New Revision: 254856 URL: https://gcc.gnu.org/viewcvs?rev=254856=gcc=rev Log: 2017-11-15 Qing Zhao PR middle-end/78809 *

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #20 from Qing Zhao --- design doc is at: https://www.mail-archive.com/gcc@gcc.gnu.org/msg83822.html

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 Paolo Carlini changed: What|Removed |Added Status|UNCONFIRMED |ASSIGNED Last reconfirmed|

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #18 from Wilco --- (In reply to Qing Zhao from comment #17) > (In reply to Wilco from comment #16) > > >> const char s[8] = “abcd\0abc”; // null byte in the middle of the string > >> int f2(void) { return __builtin_strcmp(s, "abc")

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #17 from Qing Zhao --- (In reply to Wilco from comment #16) >> const char s[8] = “abcd\0abc”; // null byte in the middle of the string >> int f2(void) { return __builtin_strcmp(s, "abc") != 0; } >> int f3(void) { return

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #16 from Wilco --- (In reply to Qing Zhao from comment #15) > (In reply to Wilco from comment 14) > > The only reason we have to do a character by character comparison is > > because we > > cannot read beyond the end of a string.

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #15 from Qing Zhao --- (In reply to Wilco from comment 14) > The only reason we have to do a character by character comparison is because > we > cannot read beyond the end of a string. However when we know the size or > alignment we

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #14 from Wilco --- (In reply to Qing Zhao from comment #11) > (In reply to Wilco from comment #9) > > > str(n)cmp with a constant string can be changed into memcmp if the string > > has a > > known alignment or is an array of known

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #13 from Qing Zhao --- (In reply to Richard Earnshaw from comment 12) > That's not entirely correct. Notionally memcmp needs to return a value > representing the relative difference of the first different byte in the > compared

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #12 from Richard Earnshaw --- (In reply to Qing Zhao from comment #7) > on the other hand, memcmp will NOT early stop, it will compare exactly N > bytes of both buffers. As a result, the compiler can compare multiple bytes > at one

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #11 from Qing Zhao --- (In reply to Wilco from comment #9) > str(n)cmp with a constant string can be changed into memcmp if the string has > a > known alignment or is an array of known size. We should check the common cases > are

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #10 from Qing Zhao --- >> From the data, we can see the inlined version of strcmp (by glibc) is much >> slower than the direct call to strcmp. (this is for size 2) >> I am using GCC farm machine gcc116: > > This result doesn't make

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #9 from Wilco --- (In reply to Qing Zhao from comment #7) str(n)cmp with a constant string can be changed into memcmp if the string has a known alignment or is an array of known size. We should check the common cases are

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #8 from Wilco --- > /home/qinzhao/Install/latest/bin/gcc -O2 t_p_1.c t_p.c > non-inlined version > 20.84user 0.00system 0:20.83elapsed 100%CPU (0avgtext+0avgdata > 360maxresident)k > 0inputs+0outputs (0major+135minor)pagefaults

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #7 from Qing Zhao --- I have studied the inlining of memcmp and str(n)cmp in GCC, the following are a summary of my study so far: 1. memcmp is different from str(n)cmp as the following: • strcmp compares

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #6 from Qing Zhao --- (A correction to comment 4: when adding #include , the call to strcmp(s, "a") was inlined by glibc in the header with the latest upstream GCC ) with attached testing case, on GCC farm machine gcc116, I got

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #5 from Qing Zhao --- Created attachment 42449 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42449=edit Run time performance testing case on aarch64 this is for testing the run-time performance of inlined version of strcmp

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 Wilco changed: What|Removed |Added CC||wdijkstr at arm dot com --- Comment #4 from

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 Qing Zhao changed: What|Removed |Added CC||qing.zhao at oracle dot com --- Comment #3

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 --- Comment #2 from wilco at gcc dot gnu.org --- (In reply to Richard Biener from comment #1) > We may have dups of this. And we now have inlining for strcmp/memcmp when > the > result is only compared against zero. I don't see that happening

[Bug middle-end/78809] Inline strcmp with small constant strings

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 Richard Biener changed: What|Removed |Added Keywords||missed-optimization --- Comment #1