https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105739
Bug ID: 105739
Summary: [9/10 Regression] Miscompilation of Linux kernel
update.c
Product: gcc
Version: 10.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jakub at gcc dot gnu.org
Target Milestone: ---
Target: x86_64-linux
The attached testcase with -fno-strict-aliasing -fno-common -fshort-wchar
-fno-PIE -std=gnu11 -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx
-fcf-protection=none -m64 -falign-jumps=1 -falign-loops=1 -mno-80387
-mno-fp-ret-in-387 -mpreferred-stack-boundary=3 -mskip-rax-setup -mtune=generic
-mno-red-zone -mcmodel=kernel -fno-asynchronous-unwind-tables
-mindirect-branch=thunk-extern -mindirect-branch-register -fno-jump-tables
-fno-delete-null-pointer-checks -O2 --param=allow-store-data-races=0
-fstack-protector-strong -fomit-frame-pointer -fno-stack-clash-protection
-fno-strict-overflow -fno-stack-check -fconserve-stack
options has a call to _printk replaced by __builtin_unreachable () and it isn't
obviously clear why.
One spot is in the rcu_tasks_trace_pertask function where in assembly one can
see:
.type rcu_tasks_trace_pertask.cold, @function
rcu_tasks_trace_pertask.cold:
.L1662:
movl 20(%rdi), %eax
.text
.size rcu_tasks_trace_pertask, .-rcu_tasks_trace_pertask
The problem went away with r11-5188-g32934a4f45a7214 but it is unclear if
that was an actual fix or just made it latent, I don't see a compound literal
on that line.
