diff --git a/src/cmd/compile/internal/gc/testdata/arith_ssa.go b/src/cmd/compile/internal/gc/testdata/arith_ssa.go
index ca96988113..2a56e2163f 100644
--- a/src/cmd/compile/internal/gc/testdata/arith_ssa.go
+++ b/src/cmd/compile/internal/gc/testdata/arith_ssa.go
@@ -141,6 +141,28 @@ func testBitwiseRshU_ssa(a uint32, b, c uint32) uint32 {
 	return a >> b >> c
 }
 
+func testShiftCX_ssa() int {
+	switch {
+	} // prevent inlining
+	v1 := uint8(3)
+	v4 := (v1 * v1) ^ v1 | v1 - v1 - v1&v1 ^ uint8(3+2) + v1*1>>0 - v1 | 1 | v1<<(2*3|0-0*0^1)
+	v5 := v4>>(3-0-uint(3)) | v1 | v1 + v1 ^ v4<<(0+1|3&1)<<(uint64(1)<<0*2*0<<0) ^ v1
+	v6 := v5 ^ (v1+v1)*v1 | v1 | v1*v1>>(v1&v1)>>(uint(1)<<0*uint(3)>>1)*v1<<2*v1<<v1 - v1>>2 | (v4 - v1) ^ v1 + v1 ^ v1>>1 | v1 + v1 - v1 ^ v1
+	v7 := v6 & v5 << 0
+	v1++
+	v11 := 2&1 ^ 0 + 3 | int(0^0)<<1>>(1*0*3) ^ 0*0 ^ 3&0*3&3 ^ 3*3 ^ 1 ^ int(2)<<(2*3) + 2 | 2 | 2 ^ 2 + 1 | 3 | 0 ^ int(1)>>1 ^ 2 // int
+	v7--
+	return int(uint64(2*1)<<(3-2)<<uint(3>>v7)-2)&v11 | v11 - int(2)<<0>>(2-1)*(v11*0&v11<<1<<(uint8(2)+v4))
+}
+
+func testShiftCX() {
+	want := 141
+	if got := testShiftCX_ssa(); want != got {
+		println("testShiftCX failed, wanted", want, "got", got)
+		failed = true
+	}
+}
+
 // testSubqToNegq ensures that the SUBQ -> NEGQ translation works correctly.
 func testSubqToNegq() {
 	want := int64(-318294940372190156)
@@ -263,6 +285,7 @@ func main() {
 	testBitwiseLogic()
 	testOcom()
 	testLrot()
+	testShiftCX()
 	testSubConst()
 
 	if failed {
diff --git a/src/cmd/compile/internal/ssa/gen/AMD64Ops.go b/src/cmd/compile/internal/ssa/gen/AMD64Ops.go
index 9e8b2fa018..6c517a950e 100644
--- a/src/cmd/compile/internal/ssa/gen/AMD64Ops.go
+++ b/src/cmd/compile/internal/ssa/gen/AMD64Ops.go
@@ -72,6 +72,7 @@ func init() {
 
 	// Common individual register masks
 	var (
+		cx     = buildReg("CX")
 		gp     = buildReg("AX CX DX BX BP SI DI R8 R9 R10 R11 R12 R13 R14 R15")
 		gpsp   = gp | buildReg("SP")
 		gpspsb = gpsp | buildReg("SB")
@@ -91,7 +92,7 @@ func init() {
 		gp11sb    = regInfo{inputs: []regMask{gpspsb}, outputs: gponly}
 		gp21      = regInfo{inputs: []regMask{gpsp, gpsp}, outputs: gponly}
 		gp21sb    = regInfo{inputs: []regMask{gpspsb, gpsp}, outputs: gponly}
-		gp21shift = regInfo{inputs: []regMask{gpsp, buildReg("CX")}, outputs: gponly}
+		gp21shift = regInfo{inputs: []regMask{gpsp, cx}, outputs: []regMask{gp &^ cx}}
 
 		gp2flags = regInfo{inputs: []regMask{gpsp, gpsp}, outputs: flagsonly}
 		gp1flags = regInfo{inputs: []regMask{gpsp}, outputs: flagsonly}
diff --git a/src/cmd/compile/internal/ssa/opGen.go b/src/cmd/compile/internal/ssa/opGen.go
index 6f412806c8..dd4462d258 100644
--- a/src/cmd/compile/internal/ssa/opGen.go
+++ b/src/cmd/compile/internal/ssa/opGen.go
@@ -1175,7 +1175,7 @@ var opcodeTable = [...]opInfo{
 				2,     // .CX
 			},
 			outputs: []regMask{
-				65519, // .AX .CX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+				65517, // .AX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
 			},
 		},
 	},
@@ -1188,7 +1188,7 @@ var opcodeTable = [...]opInfo{
 				2,     // .CX
 			},
 			outputs: []regMask{
-				65519, // .AX .CX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+				65517, // .AX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
 			},
 		},
 	},
@@ -1201,7 +1201,7 @@ var opcodeTable = [...]opInfo{
 				2,     // .CX
 			},
 			outputs: []regMask{
-				65519, // .AX .CX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+				65517, // .AX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
 			},
 		},
 	},
@@ -1214,7 +1214,7 @@ var opcodeTable = [...]opInfo{
 				2,     // .CX
 			},
 			outputs: []regMask{
-				65519, // .AX .CX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+				65517, // .AX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
 			},
 		},
 	},
@@ -1275,7 +1275,7 @@ var opcodeTable = [...]opInfo{
 				2,     // .CX
 			},
 			outputs: []regMask{
-				65519, // .AX .CX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+				65517, // .AX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
 			},
 		},
 	},
@@ -1288,7 +1288,7 @@ var opcodeTable = [...]opInfo{
 				2,     // .CX
 			},
 			outputs: []regMask{
-				65519, // .AX .CX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+				65517, // .AX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
 			},
 		},
 	},
@@ -1301,7 +1301,7 @@ var opcodeTable = [...]opInfo{
 				2,     // .CX
 			},
 			outputs: []regMask{
-				65519, // .AX .CX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+				65517, // .AX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
 			},
 		},
 	},
@@ -1314,7 +1314,7 @@ var opcodeTable = [...]opInfo{
 				2,     // .CX
 			},
 			outputs: []regMask{
-				65519, // .AX .CX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+				65517, // .AX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
 			},
 		},
 	},
@@ -1375,7 +1375,7 @@ var opcodeTable = [...]opInfo{
 				2,     // .CX
 			},
 			outputs: []regMask{
-				65519, // .AX .CX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+				65517, // .AX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
 			},
 		},
 	},
@@ -1388,7 +1388,7 @@ var opcodeTable = [...]opInfo{
 				2,     // .CX
 			},
 			outputs: []regMask{
-				65519, // .AX .CX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+				65517, // .AX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
 			},
 		},
 	},
@@ -1401,7 +1401,7 @@ var opcodeTable = [...]opInfo{
 				2,     // .CX
 			},
 			outputs: []regMask{
-				65519, // .AX .CX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+				65517, // .AX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
 			},
 		},
 	},
@@ -1414,7 +1414,7 @@ var opcodeTable = [...]opInfo{
 				2,     // .CX
 			},
 			outputs: []regMask{
-				65519, // .AX .CX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+				65517, // .AX .DX .BX .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
 			},
 		},
 	},