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cmd/compile: add support for arm64 bit-test instructions

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Add support for generating TBZ/TBNZ instructions.

The bit-test-and-branch pattern shows up in a number of
important places, including the runtime (gc bitmaps).

Before this change, there were 3 TB[N]?Z instructions in the Go tool,
all of which were in hand-written assembly. After this change, there
are 285. Also, the go1 benchmark binary gets about 4.5kB smaller.

Fixes #21361

Change-Id: I170c138b852754b9b8df149966ca5e62e6dfa771
Reviewed-on: https://go-review.googlesource.com/54470
Run-TryBot: Philip Hofer <phofer@umich.edu>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
philhofer 2017-08-09 05:01:26 +00:00 • committed by Cherry Zhang
parent 583a941d4e
commit c59b495963
15 changed files with 743 additions and 50 deletions
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4
src/cmd/compile/internal/ssa/rewrite.go
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@ -305,6 +305,10 @@ func ntz(x int64) int64 {
return 64 - nlz(^x&(x-1))
}
func oneBit(x int64) bool {
return nlz(x)+ntz(x) == 63
}
// nlo returns the number of leading ones.
func nlo(x int64) int64 {
return nlz(^x)