https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71521
Bug ID: 71521 Summary: Regression in GCC-7.0.0's optimizer Product: gcc Version: 7.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: ishiura-compiler at ml dot kwansei.ac.jp Target Milestone: --- We compiled a program (A.c) by GCC-7.0.0 and GCC-5.2.1 with -O3 option. GCC-5.2.1 performed better optimization than GCC-7.0.0. (A.c) int x = 1; int main () { int t = (1/(1>=x))>>1; if (t != 0) __builtin_abort(); return 0; } +--------------------------------------+------------------------------------+ |gcc-7.0.0.s (gcc-7.0.0 A.c -O3 -S) |gcc-5.2.1.s (gcc-5.2.1 A.c -O3 -S) | +--------------------------------------+------------------------------------+ |main: |main: | |.LFB0: |.LFB0: | | .cfi_startproc | .cfi_startproc | | cmpl $1, x(%rip) | | | jle .L2 | | | movl $1, %eax | | | xorl %ecx, %ecx | | | cltd | | | idivl %ecx | | | testl %eax, %eax | | | js .L10 | | |.L2: | | | xorl %eax, %eax | xorl %eax, %eax | | ret | ret | |.L10: | | | subq $8, %rsp | | | .cfi_def_cfa_offset 16 | | | call abort | | | .cfi_endproc | .cfi_endproc | |.LFE0: |.LFE0: | | .size main, .-main | .size main, .-main | | | .section .text.unl...| | |.LCOLDE0: | | | .section .text.sta...| | |.LHOTE0: | | .globl x | .globl x | | .data | .data | | .align 4 | .align 4 | +--------------------------------------+------------------------------------+ | .size x, 4 | .size x, 4 | |x: |x: | | .long 1 | .long 1 | | .ident "GCC: (GNU) 7.0.0 ... | .ident "GCC: (Ubuntu 5.2...| | .section .note.GNU-... | .section .note.GNU...| +--------------------------------------+------------------------------------+ using built-in spacs. COLLECT_GCC=gcc-7.0-0612 COLLECT_LTO_WRAPPER=/home/kota_kitaura/opt/gcc-7.0-0612/libexec/gcc/x86_64-pc-linux-gnu/7.0.0/lto-wrapper Target: x86_64-pc-linux-gnu configure with: ../gcc/configure --prefix=/home/kota_kitaura/opt/gcc-7.0-0612 --program-suffix=-7.0-0612 --enable-languages=c Thread model: posix gcc version 7.0.0 20160612 (experimental) (GCC) Using built-in specs. COLLECT_GCC=gcc-5 COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu 5.2.1-23ubuntu1~15.10' --with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-5 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu Thread model: posix gcc version 5.2.1 20151028 (Ubuntu 5.2.1-23ubuntu1~15.10)