https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69400
Bug ID: 69400 Summary: [5/6 Regression] wrong code with -O and int128 Product: gcc Version: 6.0 Status: UNCONFIRMED Keywords: wrong-code Severity: normal Priority: P3 Component: tree-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-*, aarch64-*, powerpc64-*, sparc64-* Created attachment 37412 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37412&action=edit reduced testcase This PR shows the problem might be more common than just ccp (PR69399). Output: $ x86_64-pc-linux-gnu-gcc -O testcase.c $ ./a.out Aborted First broken dump is .ccp1: ... Folding statement: return _3; Folded into: return 0xfffffffffffffffffffffffffffffffe; ... Thus: $ x86_64-pc-linux-gnu-gcc -O testcase.c -fno-tree-ccp $ ./a.out Aborted First broken dump is .forwprop1: ... gimple_simplified to u_2 = 0xfffffffffffffffffffffffffffffffe; gimple_simplified to _3 = 0xfffffffffffffffffffffffffffffffe; ... Thus: $ x86_64-pc-linux-gnu-gcc -O testcase.c -fno-tree-ccp -fno-tree-forwprop $ ./a.out Aborted First broken dump is .fre1: ... Replaced u_1 % 18446744073709551615 with 0xfffffffffffffffffffffffffffffffe in all uses of u_2 = u_1 % 18446744073709551615; ... Thus: $ x86_64-pc-linux-gnu-gcc -O testcase.c -fno-tree-ccp -fno-tree-forwprop -fno-tree-fre $ ./a.out Aborted I stopped there. $ x86_64-pc-linux-gnu-gcc -v Using built-in specs. COLLECT_GCC=/repo/gcc-trunk/binary-latest/bin/x86_64-pc-linux-gnu-gcc COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-232548-checking-yes-rtl-df-nographite/bin/../libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++ --enable-checking=yes,rtl,df --without-cloog --without-ppl --without-isl --disable-libstdcxx-pch --prefix=/repo/gcc-trunk//binary-trunk-232548-checking-yes-rtl-df-nographite Thread model: posix gcc version 6.0.0 20160119 (experimental) (GCC) Tested revisions: trunk r232548 - FAIL 5-branch r232545 - FAIL 4_[6789]-branch - OK