https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70903
Bug ID: 70903 Summary: [4.9/5/6/7 Regression] wrong code with bfi @ aarch64 with -Os Product: gcc Version: 7.0 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 38392 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38392&action=edit reduced testcase Output: $ 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-235588-checking-yes-rtl-df-nographite-aarch64/bin/../libexec/gcc/aarch64-unknown-linux-gnu/7.0.0/lto-wrapper Target: aarch64-unknown-linux-gnu Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++ --enable-checking=yes,rtl,df --without-cloog --without-ppl --without-isl --with-sysroot=/usr/aarch64-unknown-linux-gnu --target=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-235588-checking-yes-rtl-df-nographite-aarch64 Thread model: posix gcc version 7.0.0 20160428 (experimental) (GCC) $ aarch64-unknown-linux-gnu-gcc -Os testcase.c $ ./a.out qemu: uncaught target signal 6 (Aborted) - core dumped Aborted $ diff -u testcase.s testcase.s.fixed --- testcase.s 2016-05-02 12:57:29.920221842 +0200 +++ testcase.s.fixed 2016-05-02 12:52:41.060217727 +0200 @@ -59,7 +59,7 @@ adrp x1, .LC0 // tmp87, mov x0, x8 // tmp82, add x4, x1, :lo12:.LC0 // tmp86, tmp87, - mov x8, -1 // tmp95, + mov x8, 255 // tmp95, mov x3, 0 // D.2757, mov x2, 0 // D.2757, bfi x3, x8, 0, 8 // D.2757, tmp95,, fixes the assembly for this particular testcase. While (u8)255 == (u8)-1, x8==-1 cannot be used for 32bit load.