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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/106992] [12/13 Regression] aarch64: Unexpected maybe-uninitialized warning when compiling fdlibm Date: Wed, 21 Sep 2022 09:14:18 +0000 [thread overview] Message-ID: <bug-106992-4-KkFJ4pMaV7@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-106992-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106992 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Target|aarch64 |aarch64, x86_64-*-* Ever confirmed|0 |1 Last reconfirmed| |2022-09-21 Status|UNCONFIRMED |NEW Target Milestone|--- |12.3 Blocks| |24639 Priority|P3 |P2 Summary|aarch64: Unexpected |[12/13 Regression] aarch64: |maybe-uninitialized warning |Unexpected |when compiling fdlibm |maybe-uninitialized warning | |when compiling fdlibm CC| |rguenth at gcc dot gnu.org --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- Confirmed without -fno-strict-aliasing and with -fno-tree-vectorize -fno-strict-aliasing on x86_64. It's a bit odd - I traced walk_aliased_vdefs and indeed it didn't come along a definition of fq. We diagnose a PRE hoisted fq[0] but even with -fno-tree-pre -fno-code-hoisting we diagnose that. -fno-thread-jumps avoids the diagnostic. The reference we diagnose is introduced by thread2: k_rem_pio2.c.195t.thread2: _508 = fq[0]; This case is jump thread: (80, 136) incoming edge; (88, 90) normal (90, 94) nocopy; <bb 80> [local count: 437174]: <L145>: if (jz_117 >= 0) goto <bb 86>; [89.00%] else goto <bb 88>; [11.00%] <bb 88> [local count: 437174]: # fw_363 = PHI <fw_260(87), 0.0(80)> if (ih_111 != 0) goto <bb 90>; [50.00%] else goto <bb 89>; [50.00%] <bb 90> [local count: 218587]: iftmp.2_253 = -fw_363; *y_237(D) = iftmp.2_253; _85 = fq[0]; fw_255 = _85 - fw_363; if (jz_117 > 0) goto <bb 91>; [89.00%] else goto <bb 94>; [11.00%] so it might be that we somehow thread a jz < 0 case (which would skip the init loop) but I still can't see how ... I've used -Wall -O2 -std=c11 k_rem_pio2.c -fno-tree-vectorize -fno-strict-aliasing -fno-code-hoisting -fno-tree-pre for the above. Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24639 [Bug 24639] [meta-bug] bug to track all Wuninitialized issues
next prev parent reply other threads:[~2022-09-21 9:14 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-09-21 5:45 [Bug c/106992] New: " shqking at gmail dot com 2022-09-21 9:14 ` rguenth at gcc dot gnu.org [this message] 2023-05-08 12:25 ` [Bug tree-optimization/106992] [12/13/14 Regression] " rguenth at gcc dot gnu.org
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