From 8955a56da015890f317d5f6919391503b854d93a Mon Sep 17 00:00:00 2001
From: Joel Sing <joel@sing.id.au>
Date: Wed, 26 Feb 2020 04:00:10 +1100
Subject: [PATCH] cmd/compile: improve SignExt32to64 on riscv64

SignExt32to64 can be implemented with a single ADDIW instruction, rather than
the two shifts that are in use currently.

Change-Id: Ie1bbaef4018f1ba5162773fc64fa5a887457cfc9
Reviewed-on: https://go-review.googlesource.com/c/go/+/220922
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
---
 src/cmd/compile/internal/riscv64/ssa.go        |  2 +-
 src/cmd/compile/internal/ssa/gen/RISCV64.rules |  2 +-
 src/cmd/compile/internal/ssa/gen/RISCV64Ops.go |  1 +
 src/cmd/compile/internal/ssa/opGen.go          | 15 +++++++++++++++
 src/cmd/compile/internal/ssa/rewriteRISCV64.go | 13 ++++---------
 5 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/src/cmd/compile/internal/riscv64/ssa.go b/src/cmd/compile/internal/riscv64/ssa.go
index 2ccd3b2830..167c9a3411 100644
--- a/src/cmd/compile/internal/riscv64/ssa.go
+++ b/src/cmd/compile/internal/riscv64/ssa.go
@@ -256,7 +256,7 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
 		p.From.Reg = v.Args[0].Reg()
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = v.Reg()
-	case ssa.OpRISCV64ADDI, ssa.OpRISCV64XORI, ssa.OpRISCV64ORI, ssa.OpRISCV64ANDI,
+	case ssa.OpRISCV64ADDI, ssa.OpRISCV64ADDIW, ssa.OpRISCV64XORI, ssa.OpRISCV64ORI, ssa.OpRISCV64ANDI,
 		ssa.OpRISCV64SLLI, ssa.OpRISCV64SRAI, ssa.OpRISCV64SRLI, ssa.OpRISCV64SLTI,
 		ssa.OpRISCV64SLTIU:
 		p := s.Prog(v.Op.Asm())
diff --git a/src/cmd/compile/internal/ssa/gen/RISCV64.rules b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
index e2ac4ea5e6..720724647e 100644
--- a/src/cmd/compile/internal/ssa/gen/RISCV64.rules
+++ b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
@@ -109,7 +109,7 @@
 (SignExt8to64  <t> x) -> (SRAI [56] (SLLI <t> [56] x))
 (SignExt16to32 <t> x) -> (SRAI [48] (SLLI <t> [48] x))
 (SignExt16to64 <t> x) -> (SRAI [48] (SLLI <t> [48] x))
-(SignExt32to64 <t> x) -> (SRAI [32] (SLLI <t> [32] x))
+(SignExt32to64 <t> x) -> (ADDIW [0] x)
 
 (ZeroExt8to16  <t> x) -> (SRLI [56] (SLLI <t> [56] x))
 (ZeroExt8to32  <t> x) -> (SRLI [56] (SLLI <t> [56] x))
diff --git a/src/cmd/compile/internal/ssa/gen/RISCV64Ops.go b/src/cmd/compile/internal/ssa/gen/RISCV64Ops.go
index a1cf2e6857..7829f9a07c 100644
--- a/src/cmd/compile/internal/ssa/gen/RISCV64Ops.go
+++ b/src/cmd/compile/internal/ssa/gen/RISCV64Ops.go
@@ -129,6 +129,7 @@ func init() {
 	RISCV64ops := []opData{
 		{name: "ADD", argLength: 2, reg: gp21, asm: "ADD", commutative: true}, // arg0 + arg1
 		{name: "ADDI", argLength: 1, reg: gp11sb, asm: "ADDI", aux: "Int64"},  // arg0 + auxint
+		{name: "ADDIW", argLength: 1, reg: gp11, asm: "ADDIW", aux: "Int64"},  // 32 low bits of arg0 + auxint, sign extended to 64 bits
 		{name: "SUB", argLength: 2, reg: gp21, asm: "SUB"},                    // arg0 - arg1
 		{name: "SUBW", argLength: 2, reg: gp21, asm: "SUBW"},                  // 32 low bits of arg 0 - 32 low bits of arg 1, sign extended to 64 bits
 
diff --git a/src/cmd/compile/internal/ssa/opGen.go b/src/cmd/compile/internal/ssa/opGen.go
index a810d9fbc6..b951065e7c 100644
--- a/src/cmd/compile/internal/ssa/opGen.go
+++ b/src/cmd/compile/internal/ssa/opGen.go
@@ -1884,6 +1884,7 @@ const (
 
 	OpRISCV64ADD
 	OpRISCV64ADDI
+	OpRISCV64ADDIW
 	OpRISCV64SUB
 	OpRISCV64SUBW
 	OpRISCV64MUL
@@ -25015,6 +25016,20 @@ var opcodeTable = [...]opInfo{
 			},
 		},
 	},
+	{
+		name:    "ADDIW",
+		auxType: auxInt64,
+		argLen:  1,
+		asm:     riscv.AADDIW,
+		reg: regInfo{
+			inputs: []inputInfo{
+				{0, 1073741812}, // X3 X5 X6 X7 X8 X9 X10 X11 X12 X13 X14 X15 X16 X17 X18 X19 X20 X21 X22 X23 X24 X25 X26 X27 X28 X29 X30
+			},
+			outputs: []outputInfo{
+				{0, 1073741812}, // X3 X5 X6 X7 X8 X9 X10 X11 X12 X13 X14 X15 X16 X17 X18 X19 X20 X21 X22 X23 X24 X25 X26 X27 X28 X29 X30
+			},
+		},
+	},
 	{
 		name:   "SUB",
 		argLen: 2,
diff --git a/src/cmd/compile/internal/ssa/rewriteRISCV64.go b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
index e25f80c5ca..e4480dc366 100644
--- a/src/cmd/compile/internal/ssa/rewriteRISCV64.go
+++ b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
@@ -4109,18 +4109,13 @@ func rewriteValueRISCV64_OpSignExt16to64(v *Value) bool {
 }
 func rewriteValueRISCV64_OpSignExt32to64(v *Value) bool {
 	v_0 := v.Args[0]
-	b := v.Block
 	// match: (SignExt32to64 <t> x)
-	// result: (SRAI [32] (SLLI <t> [32] x))
+	// result: (ADDIW [0] x)
 	for {
-		t := v.Type
 		x := v_0
-		v.reset(OpRISCV64SRAI)
-		v.AuxInt = 32
-		v0 := b.NewValue0(v.Pos, OpRISCV64SLLI, t)
-		v0.AuxInt = 32
-		v0.AddArg(x)
-		v.AddArg(v0)
+		v.reset(OpRISCV64ADDIW)
+		v.AuxInt = 0
+		v.AddArg(x)
 		return true
 	}
 }
-- 
2.50.0