[llvm] Enable logf128 constant folding for hosts with 128bit long double (PR #96287)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `openmp-offload-sles-build-only` running on `rocm-worker-hw-04-sles` while building `llvm` at step 8 "Add check check-llvm".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/140/builds/3895

Here is the relevant piece of the build log for the reference:
```
Step 8 (Add check check-llvm) failure: test (failure)
******************** TEST 'LLVM :: Transforms/InstSimplify/ConstProp/logf128.ll' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 2: /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/bin/opt < /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/llvm/test/Transforms/InstSimplify/ConstProp/logf128.ll -passes=instsimplify -S | /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/bin/FileCheck /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/llvm/test/Transforms/InstSimplify/ConstProp/logf128.ll
+ /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/bin/opt -passes=instsimplify -S
+ /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/bin/FileCheck /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/llvm/test/Transforms/InstSimplify/ConstProp/logf128.ll
/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/llvm/test/Transforms/InstSimplify/ConstProp/logf128.ll:75:15: error: CHECK-NEXT: expected string not found in input
; CHECK-NEXT: ret fp128 0xL00000000000000007FFF800000000000
              ^
<stdin>:41:35: note: scanning from here
define fp128 @log_e_negative_2() {
                                  ^
<stdin>:42:2: note: possible intended match here
 ret fp128 0xL0000000000000000FFFF800000000000
 ^
/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/llvm/test/Transforms/InstSimplify/ConstProp/logf128.ll:107:15: error: CHECK-NEXT: expected string not found in input
; CHECK-NEXT: ret fp128 0xL00000000000000007FFF800000000000
              ^
<stdin>:57:42: note: scanning from here
define fp128 @log_e_negative_infinity() {
                                         ^
<stdin>:58:2: note: possible intended match here
 ret fp128 0xL0000000000000000FFFF800000000000
 ^
/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/llvm/test/Transforms/InstSimplify/ConstProp/logf128.ll:123:15: error: CHECK-NEXT: expected string not found in input
; CHECK-NEXT: ret <2 x fp128> <fp128 0xL00000000000000007FFF800000000000, fp128 0xL00000000000000007FFF800000000000>
              ^
<stdin>:65:48: note: scanning from here
define <2 x fp128> @log_e_negative_2_vector() {
                                               ^
<stdin>:66:2: note: possible intended match here
 ret <2 x fp128> <fp128 0xL0000000000000000FFFF800000000000, fp128 0xL0000000000000000FFFF800000000000>
 ^

Input file: <stdin>
Check file: /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/llvm/test/Transforms/InstSimplify/ConstProp/logf128.ll

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

Input was:
<<<<<<
            .
            .
            .
           36:  
           37: define fp128 @log_e_smallest_number_larger_than_one() { 
           38:  ret fp128 0xL00000000000000003F8F000000000000 
           39: } 
...

```

https://github.com/llvm/llvm-project/pull/96287