cmd/compile: update ABI document for loong64

The duff device has been dropped on loong64,
now we can remove related documentation.

Change-Id: I0bd721adc227522ae3c56dfe199ef735cfdf5d33
Reviewed-on: https://go-review.googlesource.com/c/go/+/740260
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>

diff --git a/src/cmd/compile/abi-internal.md b/src/cmd/compile/abi-internal.md
index a04b5aed3faccc4f8aa469d529c91b955c08903a..535acedd84b4ea0f564f87c07b98f25a49fce2f7 100644 (file)
--- a/src/cmd/compile/abi-internal.md
+++ b/src/cmd/compile/abi-internal.md
@@ -643,8 +643,6 @@ Registers R20 - R21, R23 – R28, R30 - R31, F16 – F31 are permanent scratch r
 
 Register R2 is reserved and never used.
 
-Register R20, R21 is Used by runtime.duffcopy, runtime.duffzero.
-
 Special-purpose registers used within Go generated code and Go assembly code
 are as follows:
 
@@ -653,7 +651,6 @@ are as follows:
 | R0 | Zero value | Same | Same |
 | R1 | Link register | Link register | Scratch |
 | R3 | Stack pointer | Same | Same |
-| R20,R21 | Scratch | Scratch | Used by duffcopy, duffzero |
 | R22 | Current goroutine | Same | Same |
 | R29 | Closure context pointer | Same | Same |
 | R30, R31 | used by the assembler | Same | Same |