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* [Bug c/66552] Missed optimization when shift amount is result of signed modulus [not found] <bug-66552-4@http.gcc.gnu.org/bugzilla/> @ 2015-06-17 19:33 ` msebor at gcc dot gnu.org 2015-06-30 4:34 ` [Bug rtl-optimization/66552] " segher at gcc dot gnu.org ` (3 subsequent siblings) 4 siblings, 0 replies; 5+ messages in thread From: msebor at gcc dot gnu.org @ 2015-06-17 19:33 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66552 Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |missed-optimization Target|x86/generic |x86, powerpc64 --- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> --- On powerpc64, with -O2, GCC emits the following f: srawi 9,4,5 addze 9,9 slwi 9,9,5 subf 4,9,4 srw 3,3,4 rldicl 3,3,0,32 blr while Clang emits what looks like optimal code: f: rlwinm 4, 4, 0, 27, 31 srw 3, 3, 4 blr With the return expression rewritten as suggested (i.e., x >> (n & 31)), GCC still emits an extra instruction compare to Clang. I believe this aspect is tracked in bug 66217. rldicl 4,4,0,59 srw 3,3,4 rldicl 3,3,0,32 blr ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug rtl-optimization/66552] Missed optimization when shift amount is result of signed modulus [not found] <bug-66552-4@http.gcc.gnu.org/bugzilla/> 2015-06-17 19:33 ` [Bug c/66552] Missed optimization when shift amount is result of signed modulus msebor at gcc dot gnu.org @ 2015-06-30 4:34 ` segher at gcc dot gnu.org 2015-06-30 15:52 ` msebor at gcc dot gnu.org ` (2 subsequent siblings) 4 siblings, 0 replies; 5+ messages in thread From: segher at gcc dot gnu.org @ 2015-06-30 4:34 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66552 Segher Boessenkool <segher at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Last reconfirmed| |2015-06-30 CC| |segher at gcc dot gnu.org Ever confirmed|0 |1 --- Comment #2 from Segher Boessenkool <segher at gcc dot gnu.org> --- Please file a separate bug for that last problem (it seems to be a combine problem; it has nothing to do with PR66217). You can assign it to me if you want. Confirmed, btw. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug rtl-optimization/66552] Missed optimization when shift amount is result of signed modulus [not found] <bug-66552-4@http.gcc.gnu.org/bugzilla/> 2015-06-17 19:33 ` [Bug c/66552] Missed optimization when shift amount is result of signed modulus msebor at gcc dot gnu.org 2015-06-30 4:34 ` [Bug rtl-optimization/66552] " segher at gcc dot gnu.org @ 2015-06-30 15:52 ` msebor at gcc dot gnu.org 2020-10-19 9:27 ` cvs-commit at gcc dot gnu.org 2020-10-21 3:15 ` guojiufu at gcc dot gnu.org 4 siblings, 0 replies; 5+ messages in thread From: msebor at gcc dot gnu.org @ 2015-06-30 15:52 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66552 --- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> --- (In reply to Segher Boessenkool from comment #2) I opened bug 66706. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug rtl-optimization/66552] Missed optimization when shift amount is result of signed modulus [not found] <bug-66552-4@http.gcc.gnu.org/bugzilla/> ` (2 preceding siblings ...) 2015-06-30 15:52 ` msebor at gcc dot gnu.org @ 2020-10-19 9:27 ` cvs-commit at gcc dot gnu.org 2020-10-21 3:15 ` guojiufu at gcc dot gnu.org 4 siblings, 0 replies; 5+ messages in thread From: cvs-commit at gcc dot gnu.org @ 2020-10-19 9:27 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66552 --- Comment #15 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jiu Fu Guo <guojiufu@gcc.gnu.org>: https://gcc.gnu.org/g:222f312a773157f53396ba4cb287deb07f84cc34 commit r11-4033-g222f312a773157f53396ba4cb287deb07f84cc34 Author: guojiufu <guojiufu@linux.ibm.com> Date: Mon Oct 19 13:48:19 2020 +0800 [PATCH] fold x << (n % C) to x << (n & C-1) if C meets power2 This patch fixes PR66552 which is also as: https://gcc.gnu.org/pipermail/gcc-patches/2020-February/540930.html which requests to optimizes (x shift (n mod C)) to (x shift (n bit_and (C - 1))) when C is a constant and power of two. gcc/ChangeLog 2020-10-19 Li Jia He <helijia@gcc.gnu.org> PR tree-optimization/66552 * match.pd (x << (n % C) -> x << (n & C-1)): New simplification. gcc/testsuite/ChangeLog 2020-10-19 Li Jia He <helijia@gcc.gnu.org> PR tree-optimization/66552 * gcc.dg/pr66552.c: New testcase. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug rtl-optimization/66552] Missed optimization when shift amount is result of signed modulus [not found] <bug-66552-4@http.gcc.gnu.org/bugzilla/> ` (3 preceding siblings ...) 2020-10-19 9:27 ` cvs-commit at gcc dot gnu.org @ 2020-10-21 3:15 ` guojiufu at gcc dot gnu.org 4 siblings, 0 replies; 5+ messages in thread From: guojiufu at gcc dot gnu.org @ 2020-10-21 3:15 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66552 Jiu Fu Guo <guojiufu at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED CC| |guojiufu at gcc dot gnu.org Resolution|--- |FIXED --- Comment #16 from Jiu Fu Guo <guojiufu at gcc dot gnu.org> --- Just confirmed the fix is ready in the trunk. ^ permalink raw reply [flat|nested] 5+ messages in thread
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[not found] <bug-66552-4@http.gcc.gnu.org/bugzilla/>
2015-06-17 19:33 ` [Bug c/66552] Missed optimization when shift amount is result of signed modulus msebor at gcc dot gnu.org
2015-06-30 4:34 ` [Bug rtl-optimization/66552] " segher at gcc dot gnu.org
2015-06-30 15:52 ` msebor at gcc dot gnu.org
2020-10-19 9:27 ` cvs-commit at gcc dot gnu.org
2020-10-21 3:15 ` guojiufu at gcc dot gnu.org
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