cmd/compile: unify DWARF variable generation and remove encoding

Refactor the DWARF variable generation in the compiler:

1. Replace the intermediate []byte location list encoding with a
   structured LocListEntry type. The old code packed SSA block/value
   IDs into pointer-sized integers, wrote them alongside DWARF4-format
   length-prefixed expressions, then re-read and decoded everything
   during final encoding. The new approach stores entries as
   {StartBlock, StartValue, EndBlock, EndValue, Expr} structs that
   PutLocationListDwarf4/5 directly encode into the appropriate format.
   This eliminates encodeValue, decodeValue, appendPtr, writePtr,
   readPtr, and SetupLocList, and removes the DWARF4 re-encoding in
   PutLocationListDwarf5.

2. Unify createDwarfVars into a single processing loop. The old code
   had three mutually exclusive paths (createSimpleVars, createABIVars,
   createComplexVars) selected by build mode, followed by a separate
   conservative-var loop. The new code uses one loop that tries
   createComplexVar first (when SSA debug info is available), then
   falls back to createSimpleVar. This removes createSimpleVars,
   createABIVars, and createComplexVars.

3. Extract createConservativeVar and shouldEmitDwarfVar as named
   functions, consolidating inline code and scattered filtering logic.

4. Fix createHeapDerefLocationList to return []LocListEntry instead
   of raw bytes, consistent with the new representation.

Change-Id: If6fb755c22e398d7615dccaf33b1367828e6c47e
Reviewed-on: https://go-review.googlesource.com/c/go/+/750920
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>

0 files changed, 0 insertions, 0 deletions