Dwarf: debug_info for call instruction and tracing locals

[jcivlin]

Motivation

Tracing updates in the variables requires an insertion of additional (debug-only) node into compilation graph. This however is impossible if we produce debug info in a separate module.

Therefore a design change was required and this PR implements it. In here we are removing a module dedicated for debug only: starting from this PR the DI builder writes to the same module as the compiler Builder. The added debug info consists of:

• additional debug nodes;
• metadata debug info attached to the existing compiler created nodes. The nodes does not affect anything in the llvm BE, since any optimization either knows how to update debug info, or just drops this info otherwise.

Also keep in mind that any debug related changes in the compiler graph (nodes or metadata) are activated only with "-g" compilation option. If "-g" is not set any call to a DIBuilder->func (or similar) is void.

Notable changes

1. All named local variables, %local_1 in the example below, appended with an extra debug call @llvm.dbg.declare

   store i1 %par_2_bool, ptr %local_1, align 1
   ...
   %load_store_tmp = load i1, ptr %local_1, align 1, !dbg !38
   ...
   call void @llvm.dbg.declare(metadata ptr %local_1, metadata !39, metadata !DIExpression()), !dbg !38

2. Call to a regular function is annotated with corresponding line in debug_info (only lines !2 and !39 are shown)

   %retval = call %struct.M__MyStruct @"0000000000000101_M_fun_1_AcLtMspYikxikv"(), !dbg !39
   ...
   !39 = !DILocation(line: 11, column: 39, scope: !2)
   !2 = distinct !DISubprogram(name: "fun_2", linkageName: "fun_2", scope: !1, file: !1, line: 7, type: !3, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition, unit: !0, retainedNodes: !4)

Ref issue

https://github.com/anza-xyz/move/issues/403

[ksolana]

Please move the patch from 'Draft' to 'in-review'

[jcivlin]

Thx!