https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70429
Bug ID: 70429 Summary: Wrong code with -O1. Product: gcc Version: 6.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: vsevolod.livinskij at frtk dot ru Target Milestone: --- Created attachment 38111 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38111&action=edit Reproducer. Test case produces incorrect result with -O1 and all x86 arch. Everything works fine with -O0 option. Output: > g++ -O0 repr.cpp -mavx2; ./a.out 4119272 > g++ -O1 repr.cpp -mavx2; ./a.out 272554728 GCC version: > g++ -v Using built-in specs. COLLECT_GCC=g++ COLLECT_LTO_WRAPPER=/export/users/vlivinsk/gcc-trunk/bin/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /export/users/vlivinsk/gcc-trunk/gcc/configure --with-arch=corei7 --with-cpu=corei7 --enable-clocale=gnu --with-system-zlib --enable-shared --with-demangler-in-ld --enable-cloog-backend=isl --with-fpmath=sse --enable-checking=release --enable-languages=c,c++,lto --with-gmp=/export/users/vlivinsk/gcc-trunk/gmp-6.1.0/bin --with-mpfr=/export/users/vlivinsk/gcc-trunk/mpfr-3.1.3/bin --with-mpc=/export/users/vlivinsk/gcc-trunk/mpc-1.0.3/bin --prefix=/export/users/vlivinsk/gcc-trunk/bin Thread model: posix gcc version 6.0.0 20160327 (experimental) (Revision=234496) Test: #include <iostream> #include <cstdlib> bool a = 1; int b = 612010083; void foo () { b = (int)((~7710322944595239647L + 9223372036854775807L) >> a) >> 4; } int main () { foo (); if (b != 4119272) abort(); return 0; }