https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113359
Bug ID: 113359
Summary: [13 Regression] LTO miscompilation of ceph on aarch64
Product: gcc
Version: 13.2.1
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: ---
As mentioned in https://bugzilla.redhat.com/show_bug.cgi?id=2241339
when ceph is compiled with LTO on aarch64
_M_emplace_equal<std::pair<std::chrono::time_point<ceph::mono_clock,
std::chrono::duration<unsigned long, std::ratio<1l, 1000000000l> > > const,
Context*>&>
is changed by SRA to only store 64 + 32 bits into the std::pair rather than 64
+ 64 bits.
Reproducer:
./xg++ -B ./ -O2 -flto=auto -ffat-lto-objects -fexceptions -g -Wall
-Wno-complain-wrong-lang -Werror=format-security -fstack-protector-strong
-mbranch-protection=standard -fasynchronous-unwind-tables
-fstack-clash-protection -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer
-std=c++20 -fPIC -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc
-fno-builtin-free -fno-strict-aliasing -fsigned-char -Wtype-limits
-Wignored-qualifiers -Wpointer-arith -Werror=format-security -Winit-self
-Wno-unknown-pragmas -Wnon-virtual-dtor -Wno-ignored-qualifiers
-ftemplate-depth-1024 -Wpessimizing-move -Wredundant-move
-Wstrict-null-sentinel -Woverloaded-virtual -fstack-protector-strong
-fdiagnostics-color=auto -c Timer.ii
./xg++ -B ./ -O2 -flto=auto -ffat-lto-objects -fexceptions -g -Wall
-Wno-complain-wrong-lang -Werror=format-security -fstack-protector-strong
-mbranch-protection=standard -fasynchronous-unwind-tables
-fstack-clash-protection -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer
-std=c++20 -fPIC -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc
-fno-builtin-free -fno-strict-aliasing -fsigned-char -Wtype-limits
-Wignored-qualifiers -Wpointer-arith -Werror=format-security -Winit-self
-Wno-unknown-pragmas -Wnon-virtual-dtor -Wno-ignored-qualifiers
-ftemplate-depth-1024 -Wpessimizing-move -Wredundant-move
-Wstrict-null-sentinel -Woverloaded-virtual -fstack-protector-strong
-fdiagnostics-color=auto -c SloppyCRCMap.ii
./xg++ -B ./ -O2 -c CrtStuff.i
./xg++ -B ./ -flto=auto -shared -o out.so SloppyCRCMap.o Timer.o CrtStuff.o
-nostdlib
grep_cleanup() {
c++filt | grep -A16 '_M_emplace_equal<std::pair<std::chrono.*>:' | sed
's/[^:]*: *//'
}
diff -u <(aarch64-linux-gnu-objdump -d Timer.o | grep_cleanup)
<(aarch64-linux-gnu-objdump -d out.so | grep_cleanup)
which prints
--- /dev/fd/63 2024-01-12 19:24:37.317433462 +0100
+++ /dev/fd/62 2024-01-12 19:24:37.318433448 +0100
@@ -7,11 +7,11 @@
d2800600 mov x0, #0x30 // #48
f90013f5 str x21, [sp, #32]
aa0103f5 mov x21, x1
- 94000000 bl 0 <operator new(unsigned long)>
+ 97fff0bc bl 6ee0 <operator new(unsigned long)@plt>
aa0003f4 mov x20, x0
f9400a62 ldr x2, [x19, #16]
91002263 add x3, x19, #0x8
f94002a7 ldr x7, [x21]
f9001007 str x7, [x0, #32]
- f94006a0 ldr x0, [x21, #8]
- f9001680 str x0, [x20, #40]
+ b9400aa1 ldr w1, [x21, #8]
+ b9002801 str w1, [x0, #40]
i.e. the -ffat-lto-objects non-LTO compilation stores 64-bit pointers at the
new returned pointer + 32 and + 40, while
LTO stores 64-bit pointer only to the former and 32-bit into the latter.
In *.cplxlower1 I still see
MEM[(struct pair *)_37 + 32B] = ISRA.253;
where
struct pair ISRA.253;
but sra has:
Created a replacement for ISRA.253 offset: 0, size: 64: SR.256D.22298
Created a replacement for ISRA.253 offset: 64, size: 32: SR.257D.22299
>From what I can see, that should be
std::multimap<clock_t::time_point, Context*>::value_type, i.e.
std::pair<const clock_t::time_point, Context*>
