https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115877
Bug ID: 115877
Summary: [15 Regression] wrong code at -Os (missing zero
extension)
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: zsojka at seznam dot cz
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Target: x86_64-pc-linux-gnu
Created attachment 58636
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58636&action=edit
reduced testcase
Compiler output:
$ x86_64-pc-linux-gnu-gcc -Os testcase.c
$ ./a.out
Aborted
Diff between gcc-14 and gcc-15 asm shows the issue:
--- a-testcase-14.s 2024-07-11 20:52:55.198377811 +0200
+++ a-testcase.s 2024-07-11 20:53:00.808377734 +0200
@@ -8,7 +8,6 @@
.cfi_startproc
mov ax, WORD PTR u[rip]
not eax
- movzx eax, ax
sub edi, eax
movzx eax, di
mov BYTE PTR a[rax], 1
$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-r15-1975-20240711091856-g4e0aa05f67c-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/15.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--disable-bootstrap --with-cloog --with-ppl --with-isl
--build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu
--target=x86_64-pc-linux-gnu --with-ld=/usr/bin/x86_64-pc-linux-gnu-ld
--with-as=/usr/bin/x86_64-pc-linux-gnu-as --enable-libsanitizer
--disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-r15-1975-20240711091856-g4e0aa05f67c-checking-yes-rtl-df-extra-nobootstrap-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 15.0.0 20240711 (experimental) (GCC)
