https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94178
Bug ID: 94178 Summary: [10 Regression] wrong code with -fipa-sra + invalid -Wuninitialized warning Product: gcc Version: 10.0 Status: UNCONFIRMED Keywords: wrong-code Severity: normal Priority: P3 Component: ipa Assignee: unassigned at gcc dot gnu.org Reporter: zsojka at seznam dot cz CC: marxin at gcc dot gnu.org Target Milestone: --- Host: x86_64-pc-linux-gnu Created attachment 48034 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48034&action=edit reduced testcase Output: $ x86_64-pc-linux-gnu-gcc -O -fno-dce -fipa-sra -fno-tree-dce testcase.c -Wuninitialized testcase.c: In function 'main': testcase.c:10:5: warning: 'y' is used uninitialized in this function [-Wuninitialized] 10 | y /= (u128) x; | ^~ testcase.c:8:1: note: 'y' was declared here 8 | foo (u32 x, u8 y) | ^~~ testcase.c:10:8: warning: 'x' is used uninitialized in this function [-Wuninitialized] 10 | y /= (u128) x; | ^~~~~~~~ testcase.c:8:1: note: 'x' was declared here 8 | foo (u32 x, u8 y) | ^~~ $ ./a.out Floating point exception The generated assembly code: mov edx, 0 mov ecx, 0 mov edi, 0 mov esi, 0 call __udivti3 shows it tries to do a 0/0 operation. (I failed to search gcc bugs with keyword "wrong-code", I just can't find the Keywords field at the Search page) $ 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-r10-7179-20200315012740-g9c3cdb43c2b-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/10.0.1/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 --disable-libstdcxx-pch --prefix=/repo/gcc-trunk//binary-trunk-r10-7179-20200315012740-g9c3cdb43c2b-checking-yes-rtl-df-extra-nobootstrap-amd64 Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 10.0.1 20200315 (experimental) (GCC)