[PATCH] D35994: Debug info for variables whos type is shrinked to bool

[Adrian Prantl via Phabricator via llvm-commits]

aprantl added inline comments.


================
Comment at: lib/Transforms/IPO/GlobalOpt.cpp:1577
+  for(auto *GV : GVs)
+    NewGV->addDebugInfo(GV);
+
----------------
NikolaPrica wrote:
> aprantl wrote:
> > I'm not familiar with this transformation: Do we need to add a DIExpression to mask out all but the first bit (i.e. can multiple bools be packed into the same uint32_t such that it could confuse debuggers)?
> The debug info which is provided here with addDebugInfo later generates address of the variable (DW_OP_addr: xxxx) in DW_AT_location. If we provide here metadata which is for 1byte variable  the debugger would get confused because the enum type is written as 4-byte and he would try to read 4 bytes. This is just temporary fix until proper way to handle this is found.
If I understood you correctly then the best way to represent this would be a `DW_OP_LLVM_fragment /*offset*/0 /*bitsize*/1 (or 8?)`
expression. This will get lowered into a DW_OP_bit_piece to tell the debugger that this location is describing of the first n bits of the variable.


https://reviews.llvm.org/D35994