GCCRS does not check integers for zero before division

As seen here, when dividing a variable with a statically unknown value by itself, GCCRS generates an instruction to generate the statically known value 1, based on the assumption that the denominator will not be zero.

        mov     eax, 1
        ret

However, this is not undefined behaviour in Rust, and should panic instead. The Rust reference compiler version 1.56.0 (using the default LLVM backend) also avoids using a division instruction and generates a static 1 instead, but first checks to see if the denominator is zero.

        test    rdi, rdi
        je      .LBB0_2
        mov     eax, 1
        ret
.LBB0_2:
        push    rax
        lea     rdi, [rip + str.0]
        lea     rdx, [rip + .L__unnamed_1]
        mov     esi, 25
        call    qword ptr [rip + core::panicking::panic@GOTPCREL]
        ud2

The reference compiler also avoids this when using the GCC backend.

       test    rdi, rdi
       je      .L14
       mov     eax, 1
       ret
.L14:
       push    rax
       mov     rdx, QWORD PTR global_3_example_955dbcfe_cgu_0@GOTPCREL[rip]
       mov     esi, 25
       mov     rdi, QWORD PTR str.0@GOTPCREL[rip]
       call    core::panicking::panic@PLT

The version of GCCRS being tested was gcc version 12.0.0 20210917 (experimental) (Compiler-Explorer-Build-gcc-5f0df4812c37fc428b5508e019e9fb7f8a7b77b1-binutils-2.36.1).

Reproduce the linked Compiler Explorer examples and compare GCCRS with the reference compiler for division by a possibly zero value. Trace the GCCRS integer-division handling; done means zero denominators panic while nonzero values still produce the optimized result shown in the report.