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cmd/internal/dwarf: always use AT_ranges for scopes with DWARF 5 

This patch extends the change in CL 657175 to apply the same abbrev
selection strategy to single-range lexical scopes that we're now using
for inlined routine bodies, when DWARF 5 is in effect. Ranges are more
compact and use fewer relocation than explicit hi/lo PC values, so we
might as well always use them.

Updates #26379.

Change-Id: Ieeaddf50e82acc4866010e29af32bcd1fb3b4f02
Reviewed-on: https://go-review.googlesource.com/c/go/+/657177
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
This commit is contained in:
Than McIntosh 2025-03-12 14:08:21 -04:00
parent d7f58834cb
commit bdfa604b2e
1 changed files with 6 additions and 7 deletions
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13
src/cmd/internal/dwarf/dwarf.go
View File

@ -600,12 +600,8 @@ var abbrevs = []dwAbbrev{
DW_TAG_lexical_block,
DW_CHILDREN_yes,
[]dwAttrForm{
// Note: we can't take advantage of DW_FORM_addrx here,
// since there is no way (at least at the moment) to
// have an encoding for low_pc of the form "addrx + constant"
// in DWARF5. If we wanted to use addrx, we'd need to create
// a whole new entry in .debug_addr for the block start,
// which would kind of defeat the point.
// Note: unused if we are generating DWARF 5, we
// use the ranges form even if there is a singleton range.
{DW_AT_low_pc, DW_FORM_addr},
{DW_AT_high_pc, DW_FORM_addr},
},
@ -1526,7 +1522,10 @@ func putscope(ctxt Context, s *FnState, scopes []Scope, curscope int32, fnabbrev
continue
}
if len(scope.Ranges) == 1 {
// For DWARF 5, we always use the ranges form of the abbrev, since
// it is more compact than using explicit hi/lo PC attrs. See
// issue #72821 for more on why this makes sense.
if len(scope.Ranges) == 1 && !buildcfg.Experiment.Dwarf5 {
Uleb128put(ctxt, s.Info, DW_ABRV_LEXICAL_BLOCK_SIMPLE)
putattr(ctxt, s.Info, DW_ABRV_LEXICAL_BLOCK_SIMPLE, DW_FORM_addr, DW_CLS_ADDRESS, scope.Ranges[0].Start, s.StartPC)
putattr(ctxt, s.Info, DW_ABRV_LEXICAL_BLOCK_SIMPLE, DW_FORM_addr, DW_CLS_ADDRESS, scope.Ranges[0].End, s.StartPC)