From 11c2411c5031235c709c351b65898427dcf7496c Mon Sep 17 00:00:00 2001
From: "Ruixin(Peter) Bao" <ruixin.bao@ibm.com>
Date: Thu, 22 Aug 2019 09:53:54 -0400
Subject: [PATCH] cmd/compile/internal/s390x: replace 4-byte NOP with a 2-byte
 NOP on s390x

Added a new instruction, NOPH, with the encoding [0x0700](i.e: bcr 0, 0) and
replace the current 4-byte nop that was encoded using the WORD instruction.

This reduces the size of .text section in go binary by around 17KB and make
generated code easier to read.

Change-Id: I6a756df39e93c4415ea6d038ba4af001b8ccb286
Reviewed-on: https://go-review.googlesource.com/c/go/+/194344
Reviewed-by: Michael Munday <mike.munday@ibm.com>
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
---
 src/cmd/asm/internal/asm/testdata/s390x.s | 3 +++
 src/cmd/compile/internal/s390x/ggen.go    | 5 +----
 src/cmd/internal/obj/s390x/a.out.go       | 2 ++
 src/cmd/internal/obj/s390x/anames.go      | 1 +
 src/cmd/internal/obj/s390x/asmz.go        | 6 ++++++
 5 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/src/cmd/asm/internal/asm/testdata/s390x.s b/src/cmd/asm/internal/asm/testdata/s390x.s
index c9f4d69736..4c1ca2361c 100644
--- a/src/cmd/asm/internal/asm/testdata/s390x.s
+++ b/src/cmd/asm/internal/asm/testdata/s390x.s
@@ -329,6 +329,9 @@ TEXT main·foo(SB),DUPOK|NOSPLIT,$16-0 // TEXT main.foo(SB), DUPOK|NOSPLIT, $16-
 	TCEB	F5, $8                 // ed5000080010
 	TCDB	F15, $4095             // edf00fff0011
 
+	UNDEF                          // 00000000
+	NOPH                           // 0700
+
 	VL	(R15), V1               // e710f0000006
 	VST	V1, (R15)               // e710f000000e
 	VL	(R15), V31              // e7f0f0000806
diff --git a/src/cmd/compile/internal/s390x/ggen.go b/src/cmd/compile/internal/s390x/ggen.go
index 6a72b27ac5..ae9965c378 100644
--- a/src/cmd/compile/internal/s390x/ggen.go
+++ b/src/cmd/compile/internal/s390x/ggen.go
@@ -105,8 +105,5 @@ func zeroAuto(pp *gc.Progs, n *gc.Node) {
 }
 
 func ginsnop(pp *gc.Progs) *obj.Prog {
-	p := pp.Prog(s390x.AWORD)
-	p.From.Type = obj.TYPE_CONST
-	p.From.Offset = 0x47000000 // nop 0
-	return p
+	return pp.Prog(s390x.ANOPH)
 }
diff --git a/src/cmd/internal/obj/s390x/a.out.go b/src/cmd/internal/obj/s390x/a.out.go
index d11a3834b0..08ead40f53 100644
--- a/src/cmd/internal/obj/s390x/a.out.go
+++ b/src/cmd/internal/obj/s390x/a.out.go
@@ -966,6 +966,8 @@ const (
 	AVMSLOG
 	AVMSLEOG
 
+	ANOPH // NOP
+
 	// binary
 	ABYTE
 	AWORD
diff --git a/src/cmd/internal/obj/s390x/anames.go b/src/cmd/internal/obj/s390x/anames.go
index a9bdfcafe9..2deae18b3c 100644
--- a/src/cmd/internal/obj/s390x/anames.go
+++ b/src/cmd/internal/obj/s390x/anames.go
@@ -696,6 +696,7 @@ var Anames = []string{
 	"VMSLEG",
 	"VMSLOG",
 	"VMSLEOG",
+	"NOPH",
 	"BYTE",
 	"WORD",
 	"DWORD",
diff --git a/src/cmd/internal/obj/s390x/asmz.go b/src/cmd/internal/obj/s390x/asmz.go
index 2b187edca5..d76eb25829 100644
--- a/src/cmd/internal/obj/s390x/asmz.go
+++ b/src/cmd/internal/obj/s390x/asmz.go
@@ -314,6 +314,9 @@ var optab = []Optab{
 	// undefined (deliberate illegal instruction)
 	{i: 78, as: obj.AUNDEF},
 
+	// 2 byte no-operation
+	{i: 66, as: ANOPH},
+
 	// vector instructions
 
 	// VRX store
@@ -3394,6 +3397,9 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 		d2 := c.regoff(&p.To)
 		zRXE(opcode, uint32(p.From.Reg), 0, 0, uint32(d2), 0, asm)
 
+	case 66:
+		zRR(op_BCR, 0, 0, asm)
+
 	case 67: // fmov $0 freg
 		var opcode uint32
 		switch p.As {
-- 
2.50.0