[r17-2064 Regression] FAIL: gcc.dg/tree-ssa/predcom-8.c scan-tree-dump-not pcom "Invalid sum" on Linux/x86_64

On Linux/x86_64,

470f86dd50a8adedbaa6ae9468bf42bfe89d1a36 is the first bad commit
commit 470f86dd50a8adedbaa6ae9468bf42bfe89d1a36
Author: Alfie Richards <[email protected]>
Date:   Wed Jul 1 16:01:03 2026 +0000

    fix: Check if loop_vinfo is null before dereferencing.

caused

FAIL: gcc.dg/tree-ssa/predcom-8.c scan-tree-dump-not pcom "Invalid sum"
FAIL: gcc.dg/vect/no-section-anchors-vect-31.c -flto -ffat-lto-objects  scan-tree-dump-times vect "Alignment of access forced using peeling" 2
FAIL: gcc.dg/vect/no-section-anchors-vect-31.c -flto -ffat-lto-objects  scan-tree-dump-times vect "Vectorizing an unaligned access" 0
FAIL: gcc.dg/vect/no-section-anchors-vect-31.c scan-tree-dump-times vect "Alignment of access forced using peeling" 2
FAIL: gcc.dg/vect/no-section-anchors-vect-31.c scan-tree-dump-times vect "Vectorizing an unaligned access" 0
FAIL: gcc.dg/vect/no-section-anchors-vect-64.c -flto -ffat-lto-objects  scan-tree-dump-times vect "Alignment of access forced using peeling" 2
FAIL: gcc.dg/vect/no-section-anchors-vect-64.c -flto -ffat-lto-objects  scan-tree-dump-times vect "Vectorizing an unaligned access" 0
FAIL: gcc.dg/vect/no-section-anchors-vect-64.c scan-tree-dump-times vect "Alignment of access forced using peeling" 2
FAIL: gcc.dg/vect/no-section-anchors-vect-64.c scan-tree-dump-times vect "Vectorizing an unaligned access" 0
FAIL: gcc.dg/vect/vect-56.c -flto -ffat-lto-objects  scan-tree-dump-not optimized "Invalid sum"
FAIL: gcc.dg/vect/vect-56.c scan-tree-dump-not optimized "Invalid sum"

with GCC configured with

../../gcc/configure --prefix=/export/users3/haochenj/src/gcc-bisect/master/master/r17-2064/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="tree-ssa.exp=gcc.dg/tree-ssa/predcom-8.c --target_board='unix{-m32\ -march=cascadelake}'"
$ cd {build_dir}/gcc && make check RUNTESTFLAGS="tree-ssa.exp=gcc.dg/tree-ssa/predcom-8.c --target_board='unix{-m64\ -march=cascadelake}'"
$ cd {build_dir}/gcc && make check RUNTESTFLAGS="vect.exp=gcc.dg/vect/no-section-anchors-vect-31.c --target_board='unix{-m32\ -march=cascadelake}'"
$ cd {build_dir}/gcc && make check RUNTESTFLAGS="vect.exp=gcc.dg/vect/no-section-anchors-vect-31.c --target_board='unix{-m64\ -march=cascadelake}'"
$ cd {build_dir}/gcc && make check RUNTESTFLAGS="vect.exp=gcc.dg/vect/no-section-anchors-vect-64.c --target_board='unix{-m32\ -march=cascadelake}'"
$ cd {build_dir}/gcc && make check RUNTESTFLAGS="vect.exp=gcc.dg/vect/no-section-anchors-vect-64.c --target_board='unix{-m64\ -march=cascadelake}'"
$ cd {build_dir}/gcc && make check RUNTESTFLAGS="vect.exp=gcc.dg/vect/vect-56.c --target_board='unix{-m32\ -march=cascadelake}'"
$ cd {build_dir}/gcc && make check RUNTESTFLAGS="vect.exp=gcc.dg/vect/vect-56.c --target_board='unix{-m64\ -march=cascadelake}'"

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(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.)