[llvm] [InstSimplify] Add basic constant folding for `llvm.sincos` (PR #114527)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ml-opt-rel-x86-64` running on `ml-opt-rel-x86-64-b1` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/185/builds/9816

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: Transforms/InstSimplify/sincos.ll' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 1: /b/ml-opt-rel-x86-64-b1/build/bin/opt -S -passes=instsimplify /b/ml-opt-rel-x86-64-b1/llvm-project/llvm/test/Transforms/InstSimplify/sincos.ll | /b/ml-opt-rel-x86-64-b1/build/bin/FileCheck /b/ml-opt-rel-x86-64-b1/llvm-project/llvm/test/Transforms/InstSimplify/sincos.ll
+ /b/ml-opt-rel-x86-64-b1/build/bin/opt -S -passes=instsimplify /b/ml-opt-rel-x86-64-b1/llvm-project/llvm/test/Transforms/InstSimplify/sincos.ll
+ /b/ml-opt-rel-x86-64-b1/build/bin/FileCheck /b/ml-opt-rel-x86-64-b1/llvm-project/llvm/test/Transforms/InstSimplify/sincos.ll
/b/ml-opt-rel-x86-64-b1/llvm-project/llvm/test/Transforms/InstSimplify/sincos.ll:45:15: error: CHECK-NEXT: expected string not found in input
; CHECK-NEXT: ret { <2 x float>, <2 x float> } { <2 x float> zeroinitializer, <2 x float> <float 1.000000e+00, float 1.000000e+00> }
              ^
<stdin>:24:60: note: scanning from here
define { <2 x float>, <2 x float> } @sincos_zero_vector() {
                                                           ^
<stdin>:25:2: note: possible intended match here
 ret { <2 x float>, <2 x float> } { <2 x float> zeroinitializer, <2 x float> splat (float 1.000000e+00) }
 ^

Input file: <stdin>
Check file: /b/ml-opt-rel-x86-64-b1/llvm-project/llvm/test/Transforms/InstSimplify/sincos.ll

-dump-input=help explains the following input dump.

Input was:
<<<<<<
           .
           .
           .
          19:  
          20: define { <2 x float>, <2 x float> } @sincos_vector() { 
          21:  ret { <2 x float>, <2 x float> } { <2 x float> <float 0x3FEAED5480000000, float 0x3FED18F6E0000000>, <2 x float> <float 0x3FE14A2800000000, float 0xBFDAA22660000000> } 
          22: } 
          23:  
          24: define { <2 x float>, <2 x float> } @sincos_zero_vector() { 
next:45'0                                                                X error: no match found
          25:  ret { <2 x float>, <2 x float> } { <2 x float> zeroinitializer, <2 x float> splat (float 1.000000e+00) } 
next:45'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
next:45'1      ?                                                                                                         possible intended match
          26: } 
next:45'0     ~~
          27:  
next:45'0     ~
          28: define { float, float } @sincos_poison() { 
next:45'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
          29:  %ret = call { float, float } @llvm.sincos.f32(float poison) 
          30:  ret { float, float } %ret 
           .
           .
           .
>>>>>>
...

```

</details>

https://github.com/llvm/llvm-project/pull/114527