[Bug other/67841] error: unable to find a register to spill if all registers are callee-saved

["hjl.tools at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67841

--- Comment #5 from H.J. Lu <hjl.tools at gmail dot com> ---
I updated hjl/interrupt/calls branch to update stack boundary for
use of SSE registers. Now I got

[hjl@gnu-tools-1 interrupt-1]$ cat x.i
void
__attribute__((no_caller_saved_registers))
fn (void)
{
  asm ("#"
       :
       :
       : "xmm3");
}
[hjl@gnu-tools-1 interrupt-1]$ make x.s
/export/build/gnu/gcc/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc/build-x86_64-linux/gcc/ -O2 -m32 
-mincoming-stack-boundary=2 -maccumulate-outgoing-args -S x.i
[hjl@gnu-tools-1 interrupt-1]$ cat x.s
        .file   "x.i"
        .text
        .p2align 4,,15
        .globl  fn
        .type   fn, @function
fn:
.LFB0:
        .cfi_startproc
        pushl   %ebp
        .cfi_def_cfa_offset 8
        .cfi_offset 5, -8
        movl    %esp, %ebp
        .cfi_def_cfa_register 5
        subl    $136, %esp
        andl    $-16, %esp
        movups  %xmm3, -136(%ebp)
        .cfi_offset 24, -144
#APP
# 5 "x.i" 1
        #
# 0 "" 2
#NO_APP
        movups  -136(%ebp), %xmm3
        leave
        .cfi_restore 5
        .cfi_restore 24
        .cfi_def_cfa 4, 4
        ret
        .cfi_endproc
.LFE0:
        .size   fn, .-fn
        .ident  "GCC: (GNU) 6.0.0 20151002 (experimental)"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-tools-1 interrupt-1]$ 

But is incompatible how registers are saved in prologue
which uses the original stack before realignment to save
registers.  To use aligned load/store to save vector
registers in prologue requires significant changes.