https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68026
Bug ID: 68026
Summary: Regression in GCC-6.0.0's optimizer
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
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-5.1.0 and GCC-6.0.0 with -O3 option.
GCC-5.1.0 performed better optimization than GCC-6.0.0.
(A.c)
int main (void)
{
volatile int x1 = 1;
volatile int x2 = 1;
int x3 = 2;
int t = 1;
t = 3<=(x2|1|x3|x1-1U);
if (t == 1) {}
else { __builtin_abort(); }
return 0;
}
+--------------------------------------+--------------------------------------+
| gcc-5.1.0.s (gcc-5.1.0 A.c -O3 -S) | gcc-6.0.0.s (gcc-6.0.0 A.c -O3 -S) |
+--------------------------------------+--------------------------------------+
|main: |main: |
|.LFB0: |.LFB0: |
| .cfi_startproc | .cfi_startproc |
| movl $1, -8(%rsp) | subq $24, %rsp |
| movl $1, -4(%rsp) | .cfi_def_cfa_offset 32 |
| movl -4(%rsp), %eax | movl $1, 8(%rsp) |
| movl -8(%rsp), %eax | movl $1, 12(%rsp) |
| | movl 12(%rsp), %eax |
| | movl 8(%rsp), %edx |
| | orl $3, %eax |
| | movl %eax, %ecx |
| | leal -1(%rdx), %eax |
| | orl %ecx, %eax |
| | cmpl $2, %eax |
| | jbe .L5 |
| xorl %eax, %eax | xorl %eax, %eax |
| | addq $24, %rsp |
| | .cfi_remember_state |
| | .cfi_def_cfa_offset 8 |
| ret | ret |
| |.L5: |
| | .cfi_restore_state |
| | call abort |
| .cfi_endproc | .cfi_endproc |
|.LFE0: |.LFE0: |
| .size main, .-main | .size main, .-main |
| .section .text.unlikely| .ident "GCC: (GNU) 6.0.0 ...|
|.LCOLDE0: | |
| .section .text.startup | |
|.LHOTE0: | |
| .ident "GCC: (Ubuntu 5.1.0...| |
| .section .note.GNU-s...| .section .note.GNU-s...|
+--------------------------------------+--------------------------------------+
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
5.1.0-0ubuntu11~14.04.1' --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=c++98 --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 5.1.0 (Ubuntu 5.1.0-0ubuntu11~14.04.1)
Using built-in specs.
COLLECT_GCC=gcc-6.0
COLLECT_LTO_WRAPPER=/home/iwatsuji/opt/gcc-6.0/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --prefix=/home/iwatsuji/opt/gcc-6.0
--program-suffix=-6.0 --disable-multilib --enable-languages=c
Thread model: posix
gcc version 6.0.0 20151014 (experimental) (GCC)
