Victor Mustya ad50676055 [InstCombine] Only fold bitcast(fptrunc) if destination type matches fptrunc result type. (#77046) ...

It's not enough to just make sure destination type is floating point,
because the following chain may be incorrectly optimized:
```LLVM
  %trunc = fptrunc float %src to bfloat
  %cast = bitcast bfloat %trunc to half
```
Before the fix, the instruction sequence mentioned above used to be
translated into single fptrunc instruction as follows:
```LLVM
  %trunc = fptrunc float %src to half
```

Such transformation was semantically incorrect.

2024-01-16 14:13:05 -08:00

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