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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/114902] [14/15 Regression] wrong code at -O3 with "-fno-tree-vrp -fno-expensive-optimizations -fno-tree-dominator-opts" on x86_64-linux-gnu Date: Wed, 01 May 2024 05:12:13 +0000 [thread overview] Message-ID: <bug-114902-4-QzM608EeIl@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-114902-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114902 --- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> --- here is a reduced testcase: ``` [[gnu::noipa]] int f(int b) { int tt1 = ~b; int t = 1 & tt1; int e = -t; int tt = e >= -1; if (tt) return 0; __builtin_trap(); } int main() { for(int i = -1;i < 2; i++) f(i); } ``` Note ` -O1 -fno-tree-fre -fno-tree-forwprop -fno-tree-ccp -fno-tree-dominator-opts` is needed to reproduce it with this one. The generate gimple is the same between GCC 13 and 14 here. But the first difference is in combine: ``` Trying 7 -> 8: 7: {r106:SI=r105:SI&0x1;clobber flags:CC;} REG_DEAD r105:SI REG_UNUSED flags:CC 8: {r107:SI=-r106:SI;clobber flags:CC;} REG_DEAD r106:SI REG_UNUSED flags:CC Successfully matched this instruction: (parallel [ (set (reg:SI 107 [ e_5 ]) (sign_extract:SI (reg:SI 105 [ tt1_3 ]) (const_int 1 [0x1]) (const_int 0 [0]))) (clobber (reg:CC 17 flags)) ]) allowing combination of insns 7 and 8 original costs 4 + 4 = 8 replacement cost 4 deferring deletion of insn with uid = 7. modifying insn i3 8: {r107:SI=sign_extract(r105:SI,0x1,0);clobber flags:CC;} REG_DEAD r105:SI ``` This is correct but it goes down hill after like as I mentioned in comment #2. So it does look like a latent bug after all. If someone does a bisect of this testcase, I am 99% sure you find r14-4810-ge28869670c9879 is where the failure was introduced. For the original testcase and the one in comment #1 might find a different commit due to gimple level being different.
next prev parent reply other threads:[~2024-05-01 5:12 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2024-04-30 22:13 [Bug tree-optimization/114902] New: " zhendong.su at inf dot ethz.ch 2024-05-01 2:06 ` [Bug target/114902] [14/15 Regression] " pinskia at gcc dot gnu.org 2024-05-01 2:22 ` [Bug rtl-optimization/114902] " pinskia at gcc dot gnu.org 2024-05-01 2:34 ` pinskia at gcc dot gnu.org 2024-05-01 5:12 ` pinskia at gcc dot gnu.org [this message] 2024-05-01 5:29 ` pinskia at gcc dot gnu.org 2024-05-03 8:14 ` segher at gcc dot gnu.org 2024-05-03 8:38 ` pinskia at gcc dot gnu.org 2024-05-07 7:45 ` rguenth at gcc dot gnu.org 2024-05-09 9:48 ` segher at gcc dot gnu.org 2024-05-09 9:49 ` segher at gcc dot gnu.org 2024-05-14 20:09 ` segher at gcc dot gnu.org 2024-05-14 22:04 ` pinskia at gcc dot gnu.org 2024-05-15 16:44 ` cvs-commit at gcc dot gnu.org 2024-05-15 16:54 ` [Bug rtl-optimization/114902] [14 " jakub at gcc dot gnu.org 2024-06-04 14:26 ` cvs-commit at gcc dot gnu.org 2024-06-04 14:28 ` jakub at gcc dot gnu.org 2024-06-11 6:17 ` cvs-commit at gcc dot gnu.org 2024-06-11 10:38 ` cvs-commit at gcc dot gnu.org 2024-06-20 13:23 ` cvs-commit at gcc dot gnu.org
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