https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122024
Bug ID: 122024
Summary: [16 Regression] wrong sign extension on aarch64 and
armv7 with -O2 -fwrapv
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: zsojka at seznam dot cz
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Target: aarch64-unknown-linux-gnu
Created attachment 62432
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=62432&action=edit
reduced testcase
Output:
$ aarch64-unknown-linux-gnu-gcc -O2 -fwrapv testcase.c -static
$ qemu-aarch64 -- ./a.out
qemu: uncaught target signal 6 (Aborted) - core dumped
Aborted
The value is 0x3fffffff8 instead of 0x3fff8.
The difference OK -> BAD is (aarch64):
@@ -40,9 +41,10 @@
mov x29, sp
ldrh w1, [x0, #:lo12:.LANCHOR0]
sub w1, w1, #2
+ sxth w1, w1
strh w1, [x0, #:lo12:.LANCHOR0]
ldrsw x0, [x2, 4]
- add x1, x0, w1, uxth 2
+ add x1, x0, w1, uxtw 2
adrp x0, .LC0
add x0, x0, :lo12:.LC0
str x1, [sp, 24]
$ aarch64-unknown-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-aarch64/bin/aarch64-unknown-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-20250922083307-r16-4016-g5e6937b9ab4f75-checking-yes-rtl-df-extra-aarch64/bin/../libexec/gcc/aarch64-unknown-linux-gnu/16.0.0/lto-wrapper
Target: aarch64-unknown-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--enable-libsanitizer --with-sysroot=/usr/aarch64-unknown-linux-gnu
--build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu
--target=aarch64-unknown-linux-gnu
--with-ld=/usr/bin/aarch64-unknown-linux-gnu-ld
--with-as=/usr/bin/aarch64-unknown-linux-gnu-as --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-20250922083307-r16-4016-g5e6937b9ab4f75-checking-yes-rtl-df-extra-aarch64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 16.0.0 20250922 (experimental) (GCC)
