https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116274
Bug ID: 116274
Summary: x86: poor code generation with 16 byte function
arguments
Product: gcc
Version: 14.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: ripatel at wii dot dev
Target Milestone: ---
The following program:
struct a { long x,y; };
long test(struct a a) { return a.x+a.y; }
compiled with
$ gcc -c -o test.o -march=x86-64-v2 -O3 test.c
Results in 15 x86_64 instructions using xmm registers when using the System V
calling convention, when it should be two (lea, ret).
$ objdump -d test.o
test.o: file format elf64-x86-64
Disassembly of section .text:
0000000000000000 <test>:
0: 0f 29 4c 24 e8 movaps %xmm1,-0x18(%rsp)
5: 48 8b 54 24 f0 mov -0x10(%rsp),%rdx
a: 66 48 0f 6e cf movq %rdi,%xmm1
f: 66 48 0f 6e de movq %rsi,%xmm3
14: 66 48 0f 3a 22 ca 01 pinsrq $0x1,%rdx,%xmm1
1b: 66 0f 6c cb punpcklqdq %xmm3,%xmm1
1f: 0f 29 4c 24 e8 movaps %xmm1,-0x18(%rsp)
24: 48 8b 44 24 f0 mov -0x10(%rsp),%rax
29: 66 0f 6f d1 movdqa %xmm1,%xmm2
2d: 66 48 0f 3a 22 d0 01 pinsrq $0x1,%rax,%xmm2
34: 66 0f 6f c2 movdqa %xmm2,%xmm0
38: 66 0f 73 d8 08 psrldq $0x8,%xmm0
3d: 66 0f d4 c1 paddq %xmm1,%xmm0
41: 66 48 0f 7e c0 movq %xmm0,%rax
46: c3
Debug information:
$ gcc -v -save-temps -c -o test.o -march=x86-64-v2 -O3 test.c
Using built-in specs.
COLLECT_GCC=gcc
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-redhat-linux
Configured with: ../configure --enable-bootstrap
--enable-languages=c,c++,fortran,objc,obj-c++,ada,go,d,m2,lto --prefix=/usr
--mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared
--enable-threads=posix --enable-checking=release --enable-multilib
--with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions
--enable-gnu-unique-object --enable-linker-build-id
--with-gcc-major-version-only --enable-libstdcxx-backtrace
--with-libstdcxx-zoneinfo=/usr/share/zoneinfo --with-linker-hash-style=gnu
--enable-plugin --enable-initfini-array
--with-isl=/builddir/build/BUILD/gcc-14.2.1-20240801/obj-x86_64-redhat-linux/isl-install
--enable-offload-targets=nvptx-none,amdgcn-amdhsa --enable-offload-defaulted
--without-cuda-driver --enable-gnu-indirect-function --enable-cet
--with-tune=generic --with-arch_32=i686 --build=x86_64-redhat-linux
--with-build-config=bootstrap-lto --enable-link-serialization=1
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.2.1 20240801 (Red Hat 14.2.1-1) (GCC)
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-c' '-o' 'test.o' '-march=x86-64-v2'
'-O3'
/usr/libexec/gcc/x86_64-redhat-linux/14/cc1 -E -quiet -v test.c
-march=x86-64-v2 -O3 -fpch-preprocess -o test.i
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-redhat-linux/14/include-fixed"
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-redhat-linux/14/../../../../x86_64-redhat-linux/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/lib/gcc/x86_64-redhat-linux/14/include
/usr/local/include
/usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-c' '-o' 'test.o' '-march=x86-64-v2'
'-O3'
/usr/libexec/gcc/x86_64-redhat-linux/14/cc1 -fpreprocessed test.i -quiet
-dumpbase test.c -dumpbase-ext .c -march=x86-64-v2 -O3 -version -o test.s
GNU C17 (GCC) version 14.2.1 20240801 (Red Hat 14.2.1-1) (x86_64-redhat-linux)
compiled by GNU C version 14.2.1 20240801 (Red Hat 14.2.1-1), GMP
version 6.2.1, MPFR version 4.2.1, MPC version 1.3.1, isl version isl-0.24-GMP
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 7983ab47815232989bed61515b77d1c7
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-c' '-o' 'test.o' '-march=x86-64-v2'
'-O3'
as -v --64 -o test.o test.s
GNU assembler version 2.41 (x86_64-redhat-linux) using BFD version version
2.41-37.fc40
COMPILER_PATH=/usr/libexec/gcc/x86_64-redhat-linux/14/:/usr/libexec/gcc/x86_64-redhat-linux/14/:/usr/libexec/gcc/x86_64-redhat-linux/:/usr/lib/gcc/x86_64-redhat-linux/14/:/usr/lib/gcc/x86_64-redhat-linux/
LIBRARY_PATH=/usr/lib/gcc/x86_64-redhat-linux/14/:/usr/lib/gcc/x86_64-redhat-linux/14/../../../../lib64/:/lib/../lib64/:/usr/lib/../lib64/:/usr/lib/gcc/x86_64-redhat-linux/14/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-c' '-o' 'test.o' '-march=x86-64-v2'
'-O3' '-dumpdir' 'test.'
