From: Joel Sing <joel@sing.id.au>
Date: Mon, 29 Aug 2022 20:32:09 +0000 (+1000)
Subject: cmd/compile: avoid zero extension after properly typed atomic operation on riscv64
X-Git-Tag: go1.20rc1~1155
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=b6a6847b2f33dc8fb231c78cc4d807eaf10a133a;p=gostls13.git

cmd/compile: avoid zero extension after properly typed atomic operation on riscv64

LoweredAtomicLoad8 is implemented using MOVBU, hence it is already zero
extended. LoweredAtomicCas32 and LoweredAtomicCas64 return a properly
typed boolean.

Change-Id: Ie0acbaa19403d59c7e5f76d060cc13ee51eb7834
Reviewed-on: https://go-review.googlesource.com/c/go/+/428214
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Joel Sing <joel@sing.id.au>
---

diff --git a/src/cmd/compile/internal/ssa/gen/RISCV64.rules b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
index 0207fb45d6..385f004b22 100644
--- a/src/cmd/compile/internal/ssa/gen/RISCV64.rules
+++ b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
@@ -686,6 +686,11 @@
 (MOVWUreg x:(MOVHUload _ _)) => (MOVDreg x)
 (MOVWUreg x:(MOVWUload _ _)) => (MOVDreg x)
 
+// Avoid zero extension after properly typed atomic operation.
+(MOVBUreg x:(Select0 (LoweredAtomicLoad8 _ _))) => (MOVDreg x)
+(MOVBUreg x:(Select0 (LoweredAtomicCas32 _ _ _ _))) => (MOVDreg x)
+(MOVBUreg x:(Select0 (LoweredAtomicCas64 _ _ _ _))) => (MOVDreg x)
+
 // Fold double extensions.
 (MOVBreg  x:(MOVBreg  _)) => (MOVDreg x)
 (MOVHreg  x:(MOVBreg  _)) => (MOVDreg x)
diff --git a/src/cmd/compile/internal/ssa/rewriteRISCV64.go b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
index 908456b0aa..ac0770639e 100644
--- a/src/cmd/compile/internal/ssa/rewriteRISCV64.go
+++ b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
@@ -3609,6 +3609,51 @@ func rewriteValueRISCV64_OpRISCV64MOVBUreg(v *Value) bool {
 		v.AddArg(x)
 		return true
 	}
+	// match: (MOVBUreg x:(Select0 (LoweredAtomicLoad8 _ _)))
+	// result: (MOVDreg x)
+	for {
+		x := v_0
+		if x.Op != OpSelect0 {
+			break
+		}
+		x_0 := x.Args[0]
+		if x_0.Op != OpRISCV64LoweredAtomicLoad8 {
+			break
+		}
+		v.reset(OpRISCV64MOVDreg)
+		v.AddArg(x)
+		return true
+	}
+	// match: (MOVBUreg x:(Select0 (LoweredAtomicCas32 _ _ _ _)))
+	// result: (MOVDreg x)
+	for {
+		x := v_0
+		if x.Op != OpSelect0 {
+			break
+		}
+		x_0 := x.Args[0]
+		if x_0.Op != OpRISCV64LoweredAtomicCas32 {
+			break
+		}
+		v.reset(OpRISCV64MOVDreg)
+		v.AddArg(x)
+		return true
+	}
+	// match: (MOVBUreg x:(Select0 (LoweredAtomicCas64 _ _ _ _)))
+	// result: (MOVDreg x)
+	for {
+		x := v_0
+		if x.Op != OpSelect0 {
+			break
+		}
+		x_0 := x.Args[0]
+		if x_0.Op != OpRISCV64LoweredAtomicCas64 {
+			break
+		}
+		v.reset(OpRISCV64MOVDreg)
+		v.AddArg(x)
+		return true
+	}
 	// match: (MOVBUreg x:(MOVBUreg _))
 	// result: (MOVDreg x)
 	for {