[llvm] [KnownFPClass] Refine known classes for `KnownFPClass::bitcast` (PR #215708)

[via llvm-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Linux-->
# :penguin: Linux x64 Test Results

* 180389 tests passed
* 3656 tests skipped
* 1 test failed

## Failed Tests
(click on a test name to see its output)

### LLVM
<details>
<summary>LLVM.Transforms/Attributor/nofpclass.ll</summary>

```
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 2
/home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/opt -aa-pipeline=basic-aa -passes=attributor -attributor-manifest-internal -attributor-annotate-decl-cs -S < /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/Transforms/Attributor/nofpclass.ll | /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/FileCheck --allow-unused-prefixes /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/Transforms/Attributor/nofpclass.ll --check-prefixes=CHECK,TUNIT,TUNIT-CV
# executed command: /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/opt -aa-pipeline=basic-aa -passes=attributor -attributor-manifest-internal -attributor-annotate-decl-cs -S
# note: command had no output on stdout or stderr
# executed command: /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/FileCheck --allow-unused-prefixes /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/Transforms/Attributor/nofpclass.ll --check-prefixes=CHECK,TUNIT,TUNIT-CV
# .---command stderr------------
# | /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/Transforms/Attributor/nofpclass.ll:2811:16: error: CHECK-LABEL: expected string not found in input
# | ; CHECK-LABEL: define nofpclass(zero) float @bitcast_to_float_nzero
# |                ^
# | <stdin>:1365:64: note: scanning from here
# | define nofpclass(nan inf sub norm) float @bitcast_to_float_zero(i32 %arg) #3 {
# |                                                                ^
# | <stdin>:1372:1: note: possible intended match here
# | define nofpclass(zero sub) float @bitcast_to_float_nzero(i32 %arg) #3 {
# | ^
# | 
# | Input file: <stdin>
# | Check file: /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/Transforms/Attributor/nofpclass.ll
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |               .
# |               .
# |               .
# |            1360:  %cast = bitcast i32 %or to float 
# |            1361:  ret float %cast 
# |            1362: } 
# |            1363:  
# |            1364: ; Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none) 
# |            1365: define nofpclass(nan inf sub norm) float @bitcast_to_float_zero(i32 %arg) #3 { 
# | label:2811'0                                                                   {                  search range start (exclusive)
# | label:2811'1                                                                                      error: no match found in search range
# |            1366:  %shl = shl i32 %arg, 31 
# |            1367:  %cast = bitcast i32 %shl to float 
# |            1368:  ret float %cast 
# |            1369: } 
# |            1370:  
# |            1371: ; Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none) 
# |            1372: define nofpclass(zero sub) float @bitcast_to_float_nzero(i32 %arg) #3 { 
# | label:2811'2     ?                                                                         possible intended match
# |            1373:  %or = or i32 %arg, 134217728 
# |            1374:  %cast = bitcast i32 %or to float 
# |            1375:  ret float %cast 
# |            1376: } 
# |            1377:  
# |               .
# |               .
# |               .
# |            2010: attributes #26 = { nofree nosync willreturn } 
# |            2011: attributes #27 = { nofree willreturn } 
# |            2012:  
# |            2013: !0 = !{} 
# |            2014: !1 = !{i32 3} 
# |            2015: !2 = !{i32 512} 
# | label:2811'3                     } search range end (exclusive)
# | >>>>>>
# `-----------------------------
# error: command failed with exit status: 1

--

```
</details>

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/215708