[clang] [llvm] [clang] Reland Add tanf16 builtin and support for tan constrained intrinsic (PR #94559)

[Arthur Eubanks via cfe-commits]

aeubanks wrote:

SLPVectorizer can introduce `llvm.tan.v2f32`. For example, running `opt -O3` on the following introduces `llvm.tan.v2f32`
```
target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
target triple = "thumbv7-unknown-linux-android26"

; Function Attrs: null_pointer_is_valid
define void @foo() #0 {
bb:
  %call = call float @pluto(float 1.000000e+00)
  %call1 = call i1 @ham(float %call)
  %call2 = call float @pluto(float 0.000000e+00)
  %call3 = call i1 @ham(float %call2)
  %select = select i1 %call3, float 0.000000e+00, float 1.000000e+00
  %select4 = select i1 %call1, float 0.000000e+00, float 1.000000e+00
  store float %select, ptr null, align 4
  %call5 = call ptr null(ptr null, float %select4, float 0.000000e+00, float 0.000000e+00, float 0.000000e+00)
  ret void
}

define float @pluto(float %arg) {
bb:
  %call = call float @llvm.tan.f32(float %arg)
  ret float %call
}

define i1 @ham(float %arg) {
bb:
  %fcmp = fcmp ole float %arg, 0.000000e+00
  ret i1 %fcmp
}

; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
declare float @llvm.tan.f32(float) #1

attributes #0 = { null_pointer_is_valid }
attributes #1 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
```

https://github.com/llvm/llvm-project/pull/94559