[llvm] [loongarch][DAG][FREEZE] Fix crash when FREEZE a half(f16) type on loongarch (PR #107791)

[via llvm-commits]

Felipe940402 wrote:

> For zig with LLVM 19.1.0rc4, we are seeing the following error when bootstrapping a `loongarch64-linux-musl` target.
> 
> [ziglang/zig-bootstrap#164 (comment)](https://github.com/ziglang/zig-bootstrap/issues/164#issuecomment-2332357069)
> 
> It seems that this issue is caused by `PromoteFloatResult` is not handling FREEZE OP on loongarch.
> 
> Here is the reproduction of the error: https://godbolt.org/z/PPfvWjjG5
> 
> ~This patch adds the FREEZE OP handling with `PromoteFloatRes_UnaryOp` and adds a test case.~
> 
> This patch changes loongarch's way of floating point promotion to soft promotion to avoid this problem.
> 
> See: loongarch's handling of `half`:
> 
> * [loongarch64 half (f16) failure to select with `+f` and `+d` #93894](https://github.com/llvm/llvm-project/issues/93894)
> * [[LoongArch] Allow f16 codegen with expansion to libcalls #94456](https://github.com/llvm/llvm-project/pull/94456)
> 
> Also see: other float promotion FREEZE handling
> 
> * [0019c2f](https://github.com/llvm/llvm-project/commit/0019c2f194a5e1f4cd65c5284e204328cc40ab3d)

Download 

https://github.com/llvm/llvm-project/pull/107791