[llvm-commits] [LLVM, PR11652 PATCH]: Fixed Bug 11652 - assertion failures when Type.cpp is compiled with -Os

[Stepan Dyatkovskiy]

The problem is in Type.h. The fields in Type class are declared in next 
order:
   TypeID   ID : 8;
   unsigned SubclassData : 24;
   unsigned NumContainedTys;

Attempt to set new SubclassData value rewrites lowest byte in 
NumContainedTys when -Os is set. GCC bug? Anyway setting SubclassData 
with two workaround strings fixes the problem:

  void setSubclassData(unsigned val) {
     unsigned tmp = NumContainedTys;  // Workaround for GCC -Os
     SubclassData = val;
     NumContainedTys = tmp;  // Workaround for GCC -Os
     // Ensure we don't have any accidental truncation.
     assert(SubclassData == val && "Subclass data too large for field");
   }

Probably there is another ways to protect NumContainedTys from overwritting?

Please find the patch in attachment for review.

-Stepan.
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