https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89694
Bug ID: 89694
Summary: Redundant code with optimization
Product: gcc
Version: 7.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: lavr at ncbi dot nlm.nih.gov
Target Milestone: ---
When I use the -O6 optimization, I noticed that GCC 7.4.0 interjects some
redundant code, like marked below:
mulP:
.seh_endprologue
movq %rcx, %r10
movq %rdx, %r11
movl %ecx, %eax
shrq $32, %r10
shrq $32, %r11
movl %edx, %edx // REDUNDANT
movq %r10, %r8
xorl %ecx, %ecx
imulq %r11, %r8
imulq %rdx, %r10
imulq %rax, %r11
addq %r11, %r10
setc %cl
leaq 59(%r10), %r11
jc .L6
testq %rcx, %rcx
jne .L6
cmpq $-60, %r10
cmovbe %r10, %r11
.L6:
movq %r8, %r10
salq $32, %r8
xorl %ecx, %ecx
shrq $32, %r10
imulq $59, %r10, %r9
addq %r8, %r9
setc %cl
leaq 59(%r9), %r8
jc .L11
testq %rcx, %rcx
jne .L11
cmpq $-60, %r9
cmovbe %r9, %r8
.L11:
xorl %r9d, %r9d
addq %r11, %r8
setc %r9b
movq %r8, %rcx
imulq %rax, %rdx
testq %r9, %r9
jne .L29
jne .L29 // REDUNDANT
cmpq $-60, %r8
ja .L33
.L16:
movq %rcx, %r9
salq $32, %rcx
shrq $32, %r9
imulq $59, %r9, %r8
addq %rcx, %r8
setc %cl
movq %r8, %rax
movzbl %cl, %ecx
testq %rcx, %rcx
jne .L30
jne .L30 // REDUNDANT
cmpq $-60, %r8
jbe .L17
$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-cygwin/7.4.0/lto-wrapper.exe
Target: x86_64-pc-cygwin
Configured with:
/cygdrive/i/szsz/tmpp/gcc/gcc-7.4.0-1.x86_64/src/gcc-7.4.0/configure
--srcdir=/cygdrive/i/szsz/tmpp/gcc/gcc-7.4.0-1.x86_64/src/gcc-7.4.0
--prefix=/usr --exec-prefix=/usr --localstatedir=/var --sysconfdir=/etc
--docdir=/usr/share/doc/gcc --htmldir=/usr/share/doc/gcc/html -C
--build=x86_64-pc-cygwin --host=x86_64-pc-cygwin --target=x86_64-pc-cygwin
--without-libiconv-prefix --without-libintl-prefix --libexecdir=/usr/lib
--enable-shared --enable-shared-libgcc --enable-static
--enable-version-specific-runtime-libs --enable-bootstrap --enable-__cxa_atexit
--with-dwarf2 --with-tune=generic
--enable-languages=ada,c,c++,fortran,lto,objc,obj-c++ --enable-graphite
--enable-threads=posix --enable-libatomic --enable-libcilkrts --enable-libgomp
--enable-libitm --enable-libquadmath --enable-libquadmath-support
--disable-libssp --enable-libada --disable-symvers --with-gnu-ld --with-gnu-as
--with-cloog-include=/usr/include/cloog-isl --without-libiconv-prefix
--without-libintl-prefix --with-system-zlib --enable-linker-build-id
--with-default-libstdcxx-abi=gcc4-compatible --enable-libstdcxx-filesystem-ts
Thread model: posix
gcc version 7.4.0 (GCC)
