From 2b25aaa0ed126e8a019db09247953b27123d493f Mon Sep 17 00:00:00 2001
From: Ben Shi <ben.shi@streamcomputing.com>
Date: Thu, 31 Mar 2022 14:28:08 +0000
Subject: [PATCH] cmd/internal/obj/riscv: fix illegal form of MOV instructions

---
 src/cmd/asm/internal/asm/testdata/riscv64error.s | 4 ++++
 src/cmd/internal/obj/riscv/obj.go                | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/src/cmd/asm/internal/asm/testdata/riscv64error.s b/src/cmd/asm/internal/asm/testdata/riscv64error.s
index 238552565b..d3e43e721d 100644
--- a/src/cmd/asm/internal/asm/testdata/riscv64error.s
+++ b/src/cmd/asm/internal/asm/testdata/riscv64error.s
@@ -22,5 +22,9 @@ TEXT errors(SB),$0
 	MOVBU	X5, (X6)			// ERROR "unsupported unsigned store"
 	MOVHU	X5, (X6)			// ERROR "unsupported unsigned store"
 	MOVWU	X5, (X6)			// ERROR "unsupported unsigned store"
+	MOVF	F0, F1, F2			// ERROR "illegal MOV instruction"
+	MOVD	F0, F1, F2			// ERROR "illegal MOV instruction"
+	MOV	X10, X11, X12			// ERROR "illegal MOV instruction"
+	MOVW	X10, X11, X12			// ERROR "illegal MOV instruction"
 
 	RET
diff --git a/src/cmd/internal/obj/riscv/obj.go b/src/cmd/internal/obj/riscv/obj.go
index 47dbfc0fed..61044b0531 100644
--- a/src/cmd/internal/obj/riscv/obj.go
+++ b/src/cmd/internal/obj/riscv/obj.go
@@ -1806,6 +1806,11 @@ func instructionsForMOV(p *obj.Prog) []*instruction {
 	ins := instructionForProg(p)
 	inss := []*instruction{ins}
 
+	if p.Reg != 0 {
+		p.Ctxt.Diag("%v: illegal MOV instruction", p)
+		return nil
+	}
+
 	switch {
 	case p.From.Type == obj.TYPE_CONST && p.To.Type == obj.TYPE_REG:
 		// Handle constant to register moves.