https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84748
Bug ID: 84748 Summary: [8 Regression] wrong code with u128 at aarch64 at -O and and above Product: gcc Version: 8.0 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: aarch64-unknown-linux-gnu Created attachment 43585 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43585&action=edit reduced testcase Output: $ aarch64-unknown-linux-gnu-gcc -O testcase.c -static $ ./a.out qemu: uncaught target signal 6 (Aborted) - core dumped Aborted $ 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-258314-checking-yes-rtl-df-extra-aarch64/bin/../libexec/gcc/aarch64-unknown-linux-gnu/8.0.1/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 --with-cloog --with-ppl --with-isl --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-258314-checking-yes-rtl-df-extra-aarch64 Thread model: posix gcc version 8.0.1 20180307 (experimental) (GCC) This patch: +++ testcase.s 2018-03-07 13:30:25.248052580 +0100 @@ -27,6 +27,7 @@ ldr x2, [x19, #:lo12:b] ldr x1, [x20, 8] adds x0, x0, x2 + adc x1, x4, x1 adrp x2, d ldr w2, [x2, #:lo12:d] sub w2, w2, #81920 @@ -36,7 +37,6 @@ str w2, [x3, #:lo12:c] and x2, x2, 1 mov x3, 0 - adc x1, x4, x1 bl __udivti3 str x0, [x19, #:lo12:b] str x1, [x20, 8] fixes the -O1 assembly; the "adc" is probably scheduled later by some pass, even though it crosses modification of the carry flag.