This patch both makes debug variable information it optional on
alloc_stack and alloc_box instructions, and forced variable
information on debug_value and debug_value_addr instructions. The
change of the interface uncovered a plethora of bugs in SILGen,
SILTransform, and IRGen's LoadableByAddress pass.
Most importantly this fixes the previously commented part of the
DebugInfo/local-vars.swift.gyb testcase.
rdar://problem/37720555
New data types include various forms of enums, tuples, large structs,
generics, and existentials. New contexts include switch statements
closure captures and (also) tuples.
This uncovered at least one bug so some of the CHECKs are commented out.
<rdar://problem/36031959>
For many local values we can avoid a shadow alloca by directly
describing them with a dbg.value. This also enables precise liveness
so variables don't show up in the debugger before they are
initialized. Unfortunately this also means that values will disappear
when they are no longer needed.
This patch inserts an empty inline assembler expression depending on
the llvm::Value that is being described in the blocks dominated by it.
This uses less stack space than full shadow copies *and* allows us to
track the liveness of the variable completely. It may cause values to
be spilled onto the stack, though.
<rdar://problem/26627376>
