search for: dw_op_breg

...or r-values depending on whether there is a DW_OP_stack_value/DW_OP_implicit* at the end. Yes, it might not be clear but that's what I'm trying to say. Out of the non-empty DWARF locations, register and memory locations are l-values, implicit locations are r-values. You can technically use DW_OP_breg in an l-value, but not for register locations. This is why when we have a DBG_VALUE that has a single register location operand with an otherwise empty DIExpression, we need some indicator to determine whether we want to produce the register location [DW_OP_reg] or the memory location [DW_OP_breg]...

...s each of these faithfully to DWARF, except for being unable to distinguish between the register and memory case for a single register argument. In DWARF, the difference is that a register location uses `DW_OP_reg N`, while any reference to a register's value in any other type of location uses `DW_OP_breg N`. We cannot specify these in LLVM since we only generate these operators at the end; previously, this was the job of the indirectness flag. Rather than reintroducing a flag just for this purpose however, I instead propose that we treat this as a special (albeit common) case: we can use `DW_OP_LL...

...g what the opposite (a non-exact value) would be. Apologies, "exact" was a misleading/incorrect term. By direct, I mean that the expression computes the value of the variable, as opposed to its memory address, or the value that it points to. Within LLVM, where we don't have DW_OP_reg/DW_OP_breg but instead simply refer to a generic SSA value, this could mean either a register location or stack value. > At the moment we don't make the lvalue/rvalue distinction in LLVM at all. We make an educated guess in AsmPrinter. But that's wrong and something we should strive to fix during...

...e other hand, I've been using to mean "the variable's value is equal to the value computed by the DIExpression". Applied to a DWARF expression this description would only refer to a stack value. LLVM's DIExpressions are different however, because we don't have DW_OP_reg or DW_OP_breg: we simply refer to the register and use context to determine which it should be. The best example of this is from this example[0], expanded on here with the location type: $noreg, (plus_uconst, 8), -> DW_OP_breg7 RSP+8) Memory l-value Indirect 0, (plu...