cmd/compile: tighten for huge functions in -N mode

Currently, in -N mode we skip the tighten pass. However, for very
large functions, many values live across blocks can cause
pathological behavior in the register allocator, which could use
a huge amount of memory or cause the program to hang. For
functions that large, debugging using a debugger is unlikely to be
very useful (the function is probably generated anyway). So we do
a little optimization to make fewer values live across blocks and
make it easier for the compiler.

Fixes #52180.

Change-Id: I355fe31bb87ea5d0870bb52dd06405dd5d791dab
Reviewed-on: https://go-review.googlesource.com/c/go/+/475339
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

0 files changed, 0 insertions, 0 deletions