[r17-2654 Regression] FAIL: gcc.target/i386/pr54400.c scan-assembler-times haddpd 6 on Linux/x86_64

[Haochen Jiang]

On Linux/x86_64,

fb0838bc1073aa5f22ec38e0cca2d70d625c6d71 is the first bad commit
commit fb0838bc1073aa5f22ec38e0cca2d70d625c6d71
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Jul 15 10:37:57 2026 +0200

    Support two-lane vector BB reductions without target support

caused

FAIL: gcc.target/i386/pr54400.c scan-assembler-not unpck
FAIL: gcc.target/i386/pr54400.c scan-assembler-times haddpd 6

with GCC configured with

../../gcc/configure --prefix=/export/users3/haochenj/src/gcc-bisect/master/master/r17-2654/usr --enable-clocale=gnu --with-system-zlib --with-demangler-in-ld --with-fpmath=sse --enable-languages=c,c++,fortran --enable-cet --without-isl --enable-libmpx x86_64-linux --disable-bootstrap

To reproduce:

$ cd {build_dir}/gcc && make check RUNTESTFLAGS="i386.exp=gcc.target/i386/pr54400.c --target_board='unix{-m32}'"
$ cd {build_dir}/gcc && make check RUNTESTFLAGS="i386.exp=gcc.target/i386/pr54400.c --target_board='unix{-m32\ -march=cascadelake}'"
$ cd {build_dir}/gcc && make check RUNTESTFLAGS="i386.exp=gcc.target/i386/pr54400.c --target_board='unix{-m64}'"
$ cd {build_dir}/gcc && make check RUNTESTFLAGS="i386.exp=gcc.target/i386/pr54400.c --target_board='unix{-m64\ -march=cascadelake}'"

(Please directly reply to this email for question about this report.)
(If you met problems with cascadelake related, disabling AVX512F in command line might save that.)
(However, please make sure that there is no potential problems with AVX512.)