[clang] [llvm] Emit constrained atan2 intrinsic for clang builtin (PR #113636)

[Farzon Lotfi via cfe-commits]

farzonl wrote:

> @farzonl
> 
> > Here are just a handful of tests that we might want to update, but there are others:
> 
> I'm updating these tests that were called out. What others do I need to look for? How do I know if I've found all the tests I need to update?

I found them via `git grep -n "@llvm.experimental.constrained"`

- [ ] clang/test/CodeGen/constrained-math-builtins.c
- [ ] clang/test/CodeGen/math-libcalls.c
- [x] ~~llvm/test/Assembler/fp-intrinsics-attr.ll~~
- [x] ~~llvm/test/CodeGen/AArch64/fp-intrinsics-fp16.ll~~
- [x] ~~llvm/test/CodeGen/AArch64/fp-intrinsics.ll~~
- [ ] llvm/test/CodeGen/ARM/fp-intrinsics.ll
- [ ] llvm/test/CodeGen/PowerPC/ctrloop-constrained-fp.ll
- [ ] llvm/test/CodeGen/PowerPC/ppcf128-constrained-fp-intrinsics.ll
- [ ] llvm/test/CodeGen/RISCV/double-intrinsics-strict.ll
- [ ] llvm/test/CodeGen/RISCV/float-intrinsics-strict.ll
- [ ] llvm/test/CodeGen/SystemZ/vector-constrained-fp-intrinsics.ll
- [x] ~~llvm/test/CodeGen/X86/fp-intrinsics.ll~~
- [x] ~~llvm/test/CodeGen/X86/fp-strict-libcalls-msvc32.ll~~
- [x] ~~llvm/test/CodeGen/X86/fp128-libcalls-strict.ll~~
- [x] ~~llvm/test/CodeGen/X86/fp80-strict-libcalls.ll~~
- [x] ~~llvm/test/CodeGen/X86/vector-constrained-fp-intrinsics.ll~~
- [x] ~~llvm/test/Feature/fp-intrinsics.ll~~

https://github.com/llvm/llvm-project/pull/113636