One of your optimization flags breaks the AX_C_FLOAT_WORDS_BIGENDIAN macro. The optimized object file does not have seesnoon in its data section.

$ objdump -x conftest.o conftest_unoptimized.o 

conftest.o:     file format elf64-x86-64
conftest.o
architecture: i386:x86-64, flags 0x00000011:
HAS_RELOC, HAS_SYMS
start address 0x0000000000000000

Sections:
Idx Name          Size      VMA               LMA               File off  Algn
  0 __ildata      000004eb  0000000000000000  0000000000000000  00000118  2**0
                  CONTENTS, READONLY, EXCLUDE
  1 .data         00000008  0000000000000000  0000000000000000  00000608  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, DATA
  2 .note.GNU-stack 00000000  0000000000000000  0000000000000000  00000610  2**0
                  CONTENTS, READONLY
SYMBOL TABLE:
0000000000000000 l    df *ABS*  0000000000000000 conftest.c
0000000000000000 l    d  __ildata       0000000000000000 __ildata
0000000000000000 l    d  .data  0000000000000000 .data
0000000000000000 l    d  .note.GNU-stack        0000000000000000 .note.GNU-stack
0000000000000000 g     O .data  0000000000000008 d
0000000000000000         *UND*  0000000000000000 __must_be_linked_with_icc_or_xild


RELOCATION RECORDS FOR [.data]:
OFFSET           TYPE              VALUE 
0000000000000000 R_X86_64_64       __must_be_linked_with_icc_or_xild



conftest_unoptimized.o:     file format elf64-x86-64
conftest_unoptimized.o
architecture: i386:x86-64, flags 0x00000010:
HAS_SYMS
start address 0x0000000000000000

Sections:
Idx Name          Size      VMA               LMA               File off  Algn
  0 .data         00000008  0000000000000000  0000000000000000  000000f8  2**3
                  CONTENTS, ALLOC, LOAD, DATA
  1 .bss          00000000  0000000000000000  0000000000000000  00000100  2**2
                  ALLOC
  2 .text         00000000  0000000000000000  0000000000000000  00000100  2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  3 .note.GNU-stack 00000000  0000000000000000  0000000000000000  00000100  2**0
                  CONTENTS, READONLY
SYMBOL TABLE:
0000000000000000 l    df *ABS*  0000000000000000 conftest.c
0000000000000000 l    d  .data  0000000000000000 .data
0000000000000000 l    d  .bss   0000000000000000 .bss
0000000000000000 l    d  .text  0000000000000000 .text
0000000000000000 l    d  .note.GNU-stack        0000000000000000 .note.GNU-stack
0000000000000000 g     O .data  0000000000000008 d



$ readelf -x .data conftest.o conftest_unoptimized.o 

File: conftest.o

Hex dump of section '.data':
 NOTE: This section has relocations against it, but these have NOT been applied to this dump.
  0x00000000 00000000 00000000                   ........


File: conftest_unoptimized.o

Hex dump of section '.data':
  0x00000000 73656573 6e6f6f6e                   seesnoon