[Bug middle-end/34678] Optimization generates incorrect code with -frounding-math option (#pragma STDC FENV_ACCESS not implemented)

[tkoenig at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=34678

--- Comment #48 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
Clang gets this right, even without the pragma; the original test case is
compiled to

        pushq   %r14
        pushq   %rbx
        subq    $24, %rsp
        movq    %rsi, %r14
        movq    %rdi, %rbx
        movsd   %xmm1, 16(%rsp)                 # 8-byte Spill
        movsd   %xmm0, 8(%rsp)                  # 8-byte Spill
        movl    $1024, %edi                     # imm = 0x400
        callq   fesetround@PLT
        movsd   8(%rsp), %xmm0                  # 8-byte Reload
        divsd   16(%rsp), %xmm0                 # 8-byte Folded Reload
        movsd   %xmm0, (%rbx)
        movl    $2048, %edi                     # imm = 0x800
        callq   fesetround@PLT
        movsd   8(%rsp), %xmm0                  # 8-byte Reload
        divsd   16(%rsp), %xmm0                 # 8-byte Folded Reload
        movsd   %xmm0, (%r14)
        addq    $24, %rsp
        popq    %rbx
        popq    %r14
        retq