cmd/compile/internal/bitvec: remove 2GB allocation limit in NewBulk
Remove the "NewBulk too big" check that prevented bulk bit vector
allocations exceeding ~2GB. This limit was overly restrictive and
caused compilation failures for large generated code.
The actual constraint is in the runtime's stackmap reader, which uses
int32 arithmetic. Add overflow checks in cmd/compile/internal/liveness
before stackmap serialization to detect this condition, allowing
NewBulk itself to allocate bulk large bit vector.
Fixes #77170
Change-Id: Ib7f2cabb28683258fc4e85418ba7fa70b48620b0
Reviewed-on: https://go-review.googlesource.com/c/go/+/736240
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org> Reviewed-by: Keith Randall <khr@google.com> Reviewed-by: Junyang Shao <shaojunyang@google.com>