[llvm] [CodeGen] [AMDGPU] Adds pre-commit test for fmul-select combine (PR #111107)

[Vikash Gupta via llvm-commits]

vg0204 wrote:

> Test really high powers of 2. Particularly the cases where the exponent is > 64 (or < -16) and thus no longer an inline immediate

```
define float @fmul_select_f32_test11(float %x, i32 %bool.arg1, i32 %bool.arg2) {
  %bool = icmp eq i32 %bool.arg1, %bool.arg2
  %y = select i1 %bool, float -3.0223145e+23, float -7.2057594e+16
  %ldexp = fmul float %x, %y
  ret float %ldexp
}
```
Note :  **_-3.0223145e+23 = -2^78_**  and  _**-7.2057594e+16 = -2^56**_
Whats wrong with this as it is giving this error?

```
/opt/compiler-explorer/clang-trunk/bin/llc: error: /opt/compiler-explorer/clang-trunk/bin/llc: <source>:72:31: error: floating point constant invalid for type
  %y = select i1 %bool, float -3.0223145e+23, float -7.2057594e+16
                              ^
Compiler returned: 1
```

https://github.com/llvm/llvm-project/pull/111107