[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 `llvm-clang-x86_64-gcc-ubuntu` running on `sie-linux-worker3` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/174/builds/9722

<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: /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/bin/opt -S -passes=instsimplify /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/test/Transforms/InstSimplify/sincos.ll | /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/bin/FileCheck /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/test/Transforms/InstSimplify/sincos.ll
+ /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/bin/FileCheck /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/test/Transforms/InstSimplify/sincos.ll
+ /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/bin/opt -S -passes=instsimplify /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/test/Transforms/InstSimplify/sincos.ll
/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/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: /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/test/Transforms/InstSimplify/sincos.ll

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

Input was:
<<<<<<
             1: ; ModuleID = '/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/test/Transforms/InstSimplify/sincos.ll' 
             2: source_filename = "/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/test/Transforms/InstSimplify/sincos.ll" 
             3:  
             4: define { float, float } @sincos_zero() { 
label:4'0       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
label:4'1       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
             5:  ret { float, float } { float 0.000000e+00, float 1.000000e+00 } 
next:5           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
             6: } 
             7:  
             8: define { float, float } @sincos_neg_zero() { 
label:12'0      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
label:12'1      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
             9:  ret { float, float } { float -0.000000e+00, float 1.000000e+00 } 
next:13          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            10: } 
            11:  
            12: define { float, float } @sincos_one() { 
label:20'0      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
label:20'1      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            13:  ret { float, float } { float 0x3FEAED5480000000, float 0x3FE14A2800000000 } 
next:21'0        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
next:21'1                                     ^~~~~~~~~~~~~~~~~~                              captured var "$SIN_ONE"
next:21'2                                                               ^~~~~~~~~~~~~~~~~~    captured var "$COS_ONE"
            14: } 
...

```

</details>

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