cmd/compile: improve loopRotate to handle nested loops
Enhance loop rotation of nested loops. Currently, loops are processed independently,
resulting in unnecessary jumps between outer and inner loops. By processing inner
loops before their parent loop, we ensure nested loop blocks are
properly placed within their parent loop's block sequence.
There is some code size improvement (as measured on amd64) due to jumps
to/from inner loop are removed by the updated loopRotate block order:
Executable Old .text New .text Change
-------------------------------------------------------
asm
2147569 2146481 -0.05%
cgo
1977457 1975761 -0.09%
compile
10447345 10441905 -0.05%
cover
2110097 2108977 -0.05%
link
2930289 2929041 -0.04%
preprofile 927345 926769 -0.06%
vet
3279057 3277009 -0.06%
Change-Id: I4b9e993c2be07fad735e6bcf32d062d099d9cfb5
Reviewed-on: https://go-review.googlesource.com/c/go/+/684335
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>