cmd/compile: use shift boundedness when lowering shifts on 386
Minor improvements to generated code.
file before after Δ %
runtime.s 451117 450977 -140 -0.031%
compress/bzip2.s 10202 10194 -8 -0.078%
compress/lzw.s 5924 5904 -20 -0.338%
compress/flate.s 45053 45032 -21 -0.047%
net.s 236980 236970 -10 -0.004%
vendor/golang.org/x/crypto/cryptobyte.s 29450 29439 -11 -0.037%
crypto/x509.s 107854 107840 -14 -0.013%
cmd/vendor/golang.org/x/arch/arm64/arm64asm.s 102448 102434 -14 -0.014%
cmd/internal/obj/arm.s 60536 60528 -8 -0.013%
cmd/vendor/golang.org/x/mod/sumdb/tlog.s 38273 38276 +3 +0.008%
net/http.s 462215 462201 -14 -0.003%
cmd/compile/internal/ssa.s
3951732 3954683 +2951 +0.075%
total
16946051 16948745 +2694 +0.016%
Change-Id: I9f6df1a90a295dce6fe86c8eb7576a8c96f8bb0a
Reviewed-on: https://go-review.googlesource.com/c/go/+/217000
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>