https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102608
Bug ID: 102608 Summary: [12 regression] Recent change to VN causes bogus Wuninitialized warnings & kernel build failures Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: law at gcc dot gnu.org Target Milestone: --- Created attachment 51555 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51555&action=edit Testcase This change: 55a3be2f5255d69e740d61b2c5aaba1ccbc643b8 is the first bad commit commit 55a3be2f5255d69e740d61b2c5aaba1ccbc643b8 Author: Richard Biener <rguent...@suse.de> Date: Mon Oct 4 10:57:45 2021 +0200 tree-optimization/102570 - teach VN about internal functions We're now using internal functions for a lot of stuff but there's still missing VN support out of laziness. The following instantiates support and adds testcases for FRE and PRE (hoisting). Is causing mips64-linux-gnu and mips64el-linux-gnu kernel build failures due to a bogus uninitialized warning with the attached file when compiled with -O2 -ftrivial-auto-var-init=zero: ../arch/mips/kernel/cmpxchg.c: In function '__xchg_small': ../arch/mips/kernel/cmpxchg.c:44:36: warning: 'old32' is used uninitialized [-Wuninitialized] ../arch/mips/kernel/cmpxchg.c:12:6: note: 'old32' was declared here __cmpxchg_small ../arch/mips/kernel/cmpxchg.c: In function '__cmpxchg_small': ../arch/mips/kernel/cmpxchg.c:100:36: warning: 'mask' may be used uninitialized [-Wmaybe-uninitialized] ../arch/mips/kernel/cmpxchg.c:53:6: note: 'mask' was declared here I haven't tracked this down any further.