cmd/compile/internal/escape: improve DWARF .debug_line numbering for literal rewriting optimizations

The literal rewriting optimizations to reduce user allocations
that were implemented in CL 649079 and related CLs like CL 684116
could produce .debug_line tables such that the line numbers
sometimes jumped back to a variable's declaration.

This CL adjusts the positions of the IR nodes to avoid this.

For the first test added here in i74576a.go:

  11  func main() {
  12       a := 1
  13       runtime.Breakpoint()
  14       sink = a
  15  }

Without this fix, the test reports debug lines of 12, 13, 13, 12, 14.
Note it goes backwards from 13 to a second 12.

With this fix, the test reports debug lines of 12, 13, 13, 14
without going backwards.

The test added in i74576b.go creates a slice via make with a
non-constant argument, which similarly shows debug lines going backwards
before this fix but not after. To address the slice make case, we
create a new BasicLit node to then set its position.

There were some related allocation optimizations for struct literals
such as CL 649555 during the Go 1.25 dev cycle, but at least in some
basic test cases, those optimizations did not seem to produce
debug line issues. The struct literal interface conversion test
added in i74576c.go has the same behavior before and after this change.

Finally, running 'go test ./...' in the delve repo root (4a2a6e1aeb)
seems to have many failures with go1.25rc2, but seems to pass with
this CL.

Fixes #74576
Updates #71359

Change-Id: I31faf5fe4bb352fdcd06bdc8606dbdbc4bbd65f0
Reviewed-on: https://go-review.googlesource.com/c/go/+/687815
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Alessandro Arzilli <alessandro.arzilli@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>

0 files changed, 0 insertions, 0 deletions