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)
