From 0ca355318f6c407edb4a82a0bb0c249ffd31840b Mon Sep 17 00:00:00 2001
From: Joel Sing <joel@sing.id.au>
Date: Sun, 4 Sep 2022 05:26:54 +1000
Subject: [PATCH] cmd/compile: combine masking and zero extension on riscv64

Combine masking with a negative value and zero extension into a single
AND operation.

Change-Id: I0b2a735b696d65568839fc4504445eeac3d869a6
Reviewed-on: https://go-review.googlesource.com/c/go/+/428498
Reviewed-by: Joedian Reid <joedian@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Joel Sing <joel@sing.id.au>
---
 .../compile/internal/ssa/_gen/RISCV64.rules   |  5 ++
 .../compile/internal/ssa/rewriteRISCV64.go    | 53 +++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/src/cmd/compile/internal/ssa/_gen/RISCV64.rules b/src/cmd/compile/internal/ssa/_gen/RISCV64.rules
index ad46cf30da..9882505b6b 100644
--- a/src/cmd/compile/internal/ssa/_gen/RISCV64.rules
+++ b/src/cmd/compile/internal/ssa/_gen/RISCV64.rules
@@ -667,6 +667,11 @@
 (MOVHUreg x:(ANDI [c] y)) && c >= 0 && int64(uint16(c)) == c => x
 (MOVWUreg x:(ANDI [c] y)) && c >= 0 && int64(uint32(c)) == c => x
 
+// Combine masking and zero extension.
+(MOVBUreg (ANDI [c] x)) && c < 0 => (ANDI [int64(uint8(c))] x)
+(MOVHUreg (ANDI [c] x)) && c < 0 => (ANDI [int64(uint16(c))] x)
+(MOVWUreg (ANDI [c] x)) && c < 0 => (AND (MOVDconst [int64(uint32(c))]) x)
+
 // Avoid sign/zero extension for consts.
 (MOVBreg  (MOVDconst [c])) => (MOVDconst [int64(int8(c))])
 (MOVHreg  (MOVDconst [c])) => (MOVDconst [int64(int16(c))])
diff --git a/src/cmd/compile/internal/ssa/rewriteRISCV64.go b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
index 9ec5169433..ff40a7b6ef 100644
--- a/src/cmd/compile/internal/ssa/rewriteRISCV64.go
+++ b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
@@ -3635,6 +3635,23 @@ func rewriteValueRISCV64_OpRISCV64MOVBUreg(v *Value) bool {
 		v.copyOf(x)
 		return true
 	}
+	// match: (MOVBUreg (ANDI [c] x))
+	// cond: c < 0
+	// result: (ANDI [int64(uint8(c))] x)
+	for {
+		if v_0.Op != OpRISCV64ANDI {
+			break
+		}
+		c := auxIntToInt64(v_0.AuxInt)
+		x := v_0.Args[0]
+		if !(c < 0) {
+			break
+		}
+		v.reset(OpRISCV64ANDI)
+		v.AuxInt = int64ToAuxInt(int64(uint8(c)))
+		v.AddArg(x)
+		return true
+	}
 	// match: (MOVBUreg (MOVDconst [c]))
 	// result: (MOVDconst [int64(uint8(c))])
 	for {
@@ -4341,6 +4358,23 @@ func rewriteValueRISCV64_OpRISCV64MOVHUreg(v *Value) bool {
 		v.copyOf(x)
 		return true
 	}
+	// match: (MOVHUreg (ANDI [c] x))
+	// cond: c < 0
+	// result: (ANDI [int64(uint16(c))] x)
+	for {
+		if v_0.Op != OpRISCV64ANDI {
+			break
+		}
+		c := auxIntToInt64(v_0.AuxInt)
+		x := v_0.Args[0]
+		if !(c < 0) {
+			break
+		}
+		v.reset(OpRISCV64ANDI)
+		v.AuxInt = int64ToAuxInt(int64(uint16(c)))
+		v.AddArg(x)
+		return true
+	}
 	// match: (MOVHUreg (MOVDconst [c]))
 	// result: (MOVDconst [int64(uint16(c))])
 	for {
@@ -4825,6 +4859,7 @@ func rewriteValueRISCV64_OpRISCV64MOVWUload(v *Value) bool {
 func rewriteValueRISCV64_OpRISCV64MOVWUreg(v *Value) bool {
 	v_0 := v.Args[0]
 	b := v.Block
+	typ := &b.Func.Config.Types
 	// match: (MOVWUreg x:(ANDI [c] y))
 	// cond: c >= 0 && int64(uint32(c)) == c
 	// result: x
@@ -4840,6 +4875,24 @@ func rewriteValueRISCV64_OpRISCV64MOVWUreg(v *Value) bool {
 		v.copyOf(x)
 		return true
 	}
+	// match: (MOVWUreg (ANDI [c] x))
+	// cond: c < 0
+	// result: (AND (MOVDconst [int64(uint32(c))]) x)
+	for {
+		if v_0.Op != OpRISCV64ANDI {
+			break
+		}
+		c := auxIntToInt64(v_0.AuxInt)
+		x := v_0.Args[0]
+		if !(c < 0) {
+			break
+		}
+		v.reset(OpRISCV64AND)
+		v0 := b.NewValue0(v.Pos, OpRISCV64MOVDconst, typ.UInt64)
+		v0.AuxInt = int64ToAuxInt(int64(uint32(c)))
+		v.AddArg2(v0, x)
+		return true
+	}
 	// match: (MOVWUreg (MOVDconst [c]))
 	// result: (MOVDconst [int64(uint32(c))])
 	for {