From 9439a7d87f90b97e00717fc0849d4460628d82d0 Mon Sep 17 00:00:00 2001
From: Joel Sing <joel@sing.id.au>
Date: Sun, 26 Apr 2020 04:34:34 +1000
Subject: [PATCH] cmd/compile: use SEQZ pseudo instruction in RISCV64 boolean
 rules

This makes the intent clearer, allows for another ellipsis and will aid
in future rewriting. While here, document boolean loads to explain register
contents.

Change-Id: I933db2813826d88819366191fbbea8fcee5e4dda
Reviewed-on: https://go-review.googlesource.com/c/go/+/230120
Reviewed-by: Keith Randall <khr@golang.org>
---
 .../compile/internal/ssa/gen/RISCV64.rules    |  4 ++--
 .../compile/internal/ssa/gen/RISCV64Ops.go    |  3 +++
 .../compile/internal/ssa/rewriteRISCV64.go    | 20 ++++---------------
 3 files changed, 9 insertions(+), 18 deletions(-)

diff --git a/src/cmd/compile/internal/ssa/gen/RISCV64.rules b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
index 845ca58b6ed..fbd87360ac8 100644
--- a/src/cmd/compile/internal/ssa/gen/RISCV64.rules
+++ b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
@@ -414,9 +414,9 @@
 // Boolean ops; 0=false, 1=true
 (AndB ...) => (AND ...)
 (OrB  ...) => (OR  ...)
-(EqB  x y) => (XORI [1] (XOR <typ.Bool> x y))
+(EqB  x y) => (SEQZ (XOR <typ.Bool> x y))
 (NeqB ...) => (XOR ...)
-(Not  x)   => (XORI [1] x)
+(Not  ...) => (SEQZ ...)
 
 // Lowering pointer arithmetic
 // TODO: Special handling for SP offsets, like ARM
diff --git a/src/cmd/compile/internal/ssa/gen/RISCV64Ops.go b/src/cmd/compile/internal/ssa/gen/RISCV64Ops.go
index 8bdb35f95af..8ab4abe04a0 100644
--- a/src/cmd/compile/internal/ssa/gen/RISCV64Ops.go
+++ b/src/cmd/compile/internal/ssa/gen/RISCV64Ops.go
@@ -10,6 +10,9 @@ import (
 	"fmt"
 )
 
+// Notes:
+//  - Boolean types occupy the entire register. 0=false, 1=true.
+
 // Suffixes encode the bit width of various instructions:
 //
 // D (double word) = 64 bit int
diff --git a/src/cmd/compile/internal/ssa/rewriteRISCV64.go b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
index db9f529bae0..6b91c08628b 100644
--- a/src/cmd/compile/internal/ssa/rewriteRISCV64.go
+++ b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
@@ -391,7 +391,8 @@ func rewriteValueRISCV64(v *Value) bool {
 		v.Op = OpRISCV64LoweredNilCheck
 		return true
 	case OpNot:
-		return rewriteValueRISCV64_OpNot(v)
+		v.Op = OpRISCV64SEQZ
+		return true
 	case OpOffPtr:
 		return rewriteValueRISCV64_OpOffPtr(v)
 	case OpOr16:
@@ -913,12 +914,11 @@ func rewriteValueRISCV64_OpEqB(v *Value) bool {
 	b := v.Block
 	typ := &b.Func.Config.Types
 	// match: (EqB x y)
-	// result: (XORI [1] (XOR <typ.Bool> x y))
+	// result: (SEQZ (XOR <typ.Bool> x y))
 	for {
 		x := v_0
 		y := v_1
-		v.reset(OpRISCV64XORI)
-		v.AuxInt = int64ToAuxInt(1)
+		v.reset(OpRISCV64SEQZ)
 		v0 := b.NewValue0(v.Pos, OpRISCV64XOR, typ.Bool)
 		v0.AddArg2(x, y)
 		v.AddArg(v0)
@@ -2132,18 +2132,6 @@ func rewriteValueRISCV64_OpNeqPtr(v *Value) bool {
 		return true
 	}
 }
-func rewriteValueRISCV64_OpNot(v *Value) bool {
-	v_0 := v.Args[0]
-	// match: (Not x)
-	// result: (XORI [1] x)
-	for {
-		x := v_0
-		v.reset(OpRISCV64XORI)
-		v.AuxInt = int64ToAuxInt(1)
-		v.AddArg(x)
-		return true
-	}
-}
 func rewriteValueRISCV64_OpOffPtr(v *Value) bool {
 	v_0 := v.Args[0]
 	b := v.Block