assembler errors when bootstrapping with #pragma optimize "0"

[Martin Sebor via Gcc]

I put #pragma GCC optimize "0" at the top of gimplify.c to help
me debug something in a bootstrapped compiler.  The file failed
to compile with many assembler errors like this:
/tmp/ccL9zcXD.s: Assembler messages:
/tmp/ccL9zcXD.s:9: Error: CFI instruction used without previous 
.cfi_startproc

I've done this before and had no problems.  Is this supposed to
work or was I just lucky when it did before?

Thanks
Martin

PS The top of gimplify.s is below (this is with no other code
changes to any files except the #pragma).

        .file   "gimplify.c"
        .text
        .local  _ZZ20gimplify_va_arg_exprPP9tree_nodePP6gimpleS4_E9gave_help
        .comm   _ZZ20gimplify_va_arg_exprPP9tree_nodePP6gimpleS4_E9gave_help,1,1
        .p2align 4
        .type   _ZL19handled_component_pPK9tree_node, @function
_ZL19handled_component_pPK9tree_node:
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        movq    %rsp, %rbp
        .cfi_def_cfa_register 6
        movq    %rdi, -8(%rbp)
        movq    -8(%rbp), %rax
        movzwl  (%rax), %eax
        movzwl  %ax, %eax
        subl    $47, %eax
        cmpl    $6, %eax
        ja      .L2
        movl    $1, %eax
        jmp     .L3
.L2:
        movl    $0, %eax
.L3:
        popq    %rbp
        .cfi_def_cfa 7, 8
        ret