From 125eca0f7210da1bbf1a4a1460a87d1c33366b99 Mon Sep 17 00:00:00 2001
From: Joel Sing <joel@sing.id.au>
Date: Sat, 6 Mar 2021 04:46:07 +1100
Subject: [PATCH] cmd/compile: improve IsNonNil rule on riscv64

IsNonNil is readily implemented using SNEZ on riscv64, removing over 8,000
instructions from the go binary. Other rules will improve on this sequence,
however in this case it makes sense to use a direct simplification.

Change-Id: Ib4068599532398afcd05f51d160673ef5fb5e5a0
Reviewed-on: https://go-review.googlesource.com/c/go/+/299230
Trust: Joel Sing <joel@sing.id.au>
Reviewed-by: Michael Munday <mike.munday@lowrisc.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
---
 src/cmd/compile/internal/ssa/gen/RISCV64.rules |  2 +-
 src/cmd/compile/internal/ssa/rewriteRISCV64.go | 18 ++----------------
 2 files changed, 3 insertions(+), 17 deletions(-)

diff --git a/src/cmd/compile/internal/ssa/gen/RISCV64.rules b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
index d7efef039e9..dbe04f1d588 100644
--- a/src/cmd/compile/internal/ssa/gen/RISCV64.rules
+++ b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
@@ -423,7 +423,7 @@
 (Convert ...) => (MOVconvert ...)
 
 // Checks
-(IsNonNil p) => (NeqPtr (MOVDconst [0]) p)
+(IsNonNil ...) => (SNEZ ...)
 (IsInBounds ...) => (Less64U ...)
 (IsSliceInBounds ...) => (Leq64U ...)
 
diff --git a/src/cmd/compile/internal/ssa/rewriteRISCV64.go b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
index 7f77477da74..895f380d338 100644
--- a/src/cmd/compile/internal/ssa/rewriteRISCV64.go
+++ b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
@@ -239,7 +239,8 @@ func rewriteValueRISCV64(v *Value) bool {
 		v.Op = OpLess64U
 		return true
 	case OpIsNonNil:
-		return rewriteValueRISCV64_OpIsNonNil(v)
+		v.Op = OpRISCV64SNEZ
+		return true
 	case OpIsSliceInBounds:
 		v.Op = OpLeq64U
 		return true
@@ -1101,21 +1102,6 @@ func rewriteValueRISCV64_OpHmul32u(v *Value) bool {
 		return true
 	}
 }
-func rewriteValueRISCV64_OpIsNonNil(v *Value) bool {
-	v_0 := v.Args[0]
-	b := v.Block
-	typ := &b.Func.Config.Types
-	// match: (IsNonNil p)
-	// result: (NeqPtr (MOVDconst [0]) p)
-	for {
-		p := v_0
-		v.reset(OpNeqPtr)
-		v0 := b.NewValue0(v.Pos, OpRISCV64MOVDconst, typ.UInt64)
-		v0.AuxInt = int64ToAuxInt(0)
-		v.AddArg2(v0, p)
-		return true
-	}
-}
 func rewriteValueRISCV64_OpLeq16(v *Value) bool {
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]