[Bug middle-end/126410] New: vectorizer aligns 16-byte array to 64byte

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126410

            Bug ID: 126410
           Summary: vectorizer aligns 16-byte array to 64byte
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com
  Target Milestone: ---

[hjl@gnu-tgl-3 pr126403]$ cat foo.c
#define N 4

typedef struct { float values[N]; } vector;

extern vector v;

extern void foo (vector *);

void
func (vector a, vector b)
{
  vector r;
  for (int i = 0; i < N; i++)
    r.values[i] = a.values[i] * b.values[i];
  foo (&r);
}
[hjl@gnu-tgl-3 pr126403]$ gcc -O2 -S foo.c -march=x86-64-v4 
[hjl@gnu-tgl-3 pr126403]$ cat foo.s
        .file   "foo.c"
        .text
        .p2align 4
        .globl  func
        .type   func, @function
func:
.LFB0:
        .cfi_startproc
        vpextrq $1, %xmm4, %rdx
        vmovdqa %xmm0, %xmm4
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        vpinsrq $1, %rdx, %xmm4, %xmm4
        vpextrq $1, %xmm5, %rdx
        vmovdqa %xmm2, %xmm5
        vpinsrq $1, %rdx, %xmm5, %xmm5
        vpunpcklqdq     %xmm1, %xmm4, %xmm4
        vpunpcklqdq     %xmm3, %xmm5, %xmm5
        movq    %rsp, %rbp
        .cfi_def_cfa_register 6
        andq    $-64, %rsp    <<< Not needd.
        vmulps  %xmm5, %xmm4, %xmm1
        subq    $64, %rsp
        movq    %rsp, %rdi
        vmovaps %xmm1, (%rsp)
        call    foo
        leave
        .cfi_def_cfa 7, 8
        ret
        .cfi_endproc
.LFE0:
        .size   func, .-func
        .ident  "GCC: (GNU) 16.1.1 20260703 (Red Hat 16.1.1-4)"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-tgl-3 pr126403]$ 



Breakpoint 1, ensure_base_align (dr_info=0x4f58288)
    at /export/gnu/import/git/gitlab/x86-gcc/gcc/tree-vect-stmts.cc:7189
7189            DR_TARGET_ALIGNMENT (dr_info).to_constant () * BITS_PER_UNIT;
Missing rpms, try: dnf --enablerepo='*debug*' install
isl-debuginfo-0.16.1-24.0.fc44.x86_64 libmpc-debuginfo-1.4.1-1.fc44.x86_64
mpfr-debuginfo-4.2.2-3.fc44.x86_64 gmp-debuginfo-6.3.0-5.0.fc44.x86_64
zlib-ng-compat-debuginfo-2.3.3-3.fc44.x86_64
libzstd-debuginfo-1.5.7-5.fc44.x86_64 glibc-debuginfo-2.43-7.0.fc44.x86_64
(gdb) next
7191          if (decl_in_symtab_p (base_decl))
(gdb) p align_base_to
$1 = 512
(gdb) 

Why does DR_TARGET_ALIGNMENT (dr_info).to_constant () return 64 bytes?