diff --git a/src/cmd/compile/internal/ssa/config.go b/src/cmd/compile/internal/ssa/config.go
index 7d345ae280..5e54f4f96f 100644
--- a/src/cmd/compile/internal/ssa/config.go
+++ b/src/cmd/compile/internal/ssa/config.go
@@ -13,16 +13,17 @@ import (
 )
 
 type Config struct {
-	arch       string                     // "amd64", etc.
-	IntSize    int64                      // 4 or 8
-	PtrSize    int64                      // 4 or 8
-	lowerBlock func(*Block) bool          // lowering function
-	lowerValue func(*Value, *Config) bool // lowering function
-	fe         Frontend                   // callbacks into compiler frontend
-	HTML       *HTMLWriter                // html writer, for debugging
-	ctxt       *obj.Link                  // Generic arch information
-	optimize   bool                       // Do optimization
-	curFunc    *Func
+	arch         string                     // "amd64", etc.
+	IntSize      int64                      // 4 or 8
+	PtrSize      int64                      // 4 or 8
+	lowerBlock   func(*Block) bool          // lowering function
+	lowerValue   func(*Value, *Config) bool // lowering function
+	fe           Frontend                   // callbacks into compiler frontend
+	HTML         *HTMLWriter                // html writer, for debugging
+	ctxt         *obj.Link                  // Generic arch information
+	optimize     bool                       // Do optimization
+	noDuffDevice bool                       // Don't use Duff's device
+	curFunc      *Func
 
 	// TODO: more stuff. Compiler flags of interest, ...
 
@@ -122,6 +123,12 @@ func NewConfig(arch string, fe Frontend, ctxt *obj.Link, optimize bool) *Config
 	c.ctxt = ctxt
 	c.optimize = optimize
 
+	// Don't use Duff's device on Plan 9, because floating
+	// point operations are not allowed in note handler.
+	if obj.Getgoos() == "plan9" {
+		c.noDuffDevice = true
+	}
+
 	// Assign IDs to preallocated values/blocks.
 	for i := range c.values {
 		c.values[i].ID = ID(i)
diff --git a/src/cmd/compile/internal/ssa/gen/AMD64.rules b/src/cmd/compile/internal/ssa/gen/AMD64.rules
index 25a8861130..73fa700d93 100644
--- a/src/cmd/compile/internal/ssa/gen/AMD64.rules
+++ b/src/cmd/compile/internal/ssa/gen/AMD64.rules
@@ -328,7 +328,7 @@
 		(MOVOstore dst (MOVOload src mem) mem))
 
 // Medium copying uses a duff device.
-(Move [size] dst src mem) && size >= 32 && size <= 16*64 && size%16 == 0 ->
+(Move [size] dst src mem) && size >= 32 && size <= 16*64 && size%16 == 0 && !config.noDuffDevice ->
 	(DUFFCOPY [14*(64-size/16)] dst src mem)
 // 14 and 64 are magic constants.  14 is the number of bytes to encode:
 //	MOVUPS	(SI), X0
@@ -338,7 +338,7 @@
 // and 64 is the number of such blocks. See src/runtime/duff_amd64.s:duffcopy.
 
 // Large copying uses REP MOVSQ.
-(Move [size] dst src mem) && size > 16*64 && size%8 == 0 ->
+(Move [size] dst src mem) && (size > 16*64 || config.noDuffDevice) && size%8 == 0 ->
 	(REPMOVSQ dst src (MOVQconst [size/8]) mem)
 
 (Not x) -> (XORBconst [1] x)
@@ -869,13 +869,13 @@
 				(MOVQstoreconst [0] destptr mem))))
 
 // Medium zeroing uses a duff device.
-(Zero [size] destptr mem) && size <= 1024 && size%8 == 0 && size%16 != 0 ->
+(Zero [size] destptr mem) && size <= 1024 && size%8 == 0 && size%16 != 0 && !config.noDuffDevice ->
 	(Zero [size-8] (ADDQconst [8] destptr) (MOVQstore destptr (MOVQconst [0]) mem))
-(Zero [size] destptr mem) && size <= 1024 && size%16 == 0 ->
+(Zero [size] destptr mem) && size <= 1024 && size%16 == 0 && !config.noDuffDevice ->
 	(DUFFZERO [duffStart(size)] (ADDQconst [duffAdj(size)] destptr) (MOVOconst [0]) mem)
 
 // Large zeroing uses REP STOSQ.
-(Zero [size] destptr mem) && size > 1024 && size%8 == 0 ->
+(Zero [size] destptr mem) && (size > 1024 || (config.noDuffDevice && size > 32)) && size%8 == 0 ->
 	(REPSTOSQ destptr (MOVQconst [size/8]) (MOVQconst [0]) mem)
 
 // Absorb InvertFlags into branches.
diff --git a/src/cmd/compile/internal/ssa/rewriteAMD64.go b/src/cmd/compile/internal/ssa/rewriteAMD64.go
index 83fc437747..bed44ef103 100644
--- a/src/cmd/compile/internal/ssa/rewriteAMD64.go
+++ b/src/cmd/compile/internal/ssa/rewriteAMD64.go
@@ -8811,14 +8811,14 @@ func rewriteValueAMD64_OpMove(v *Value, config *Config) bool {
 		return true
 	}
 	// match: (Move [size] dst src mem)
-	// cond: size >= 32 && size <= 16*64 && size%16 == 0
+	// cond: size >= 32 && size <= 16*64 && size%16 == 0 && !config.noDuffDevice
 	// result: (DUFFCOPY [14*(64-size/16)] dst src mem)
 	for {
 		size := v.AuxInt
 		dst := v.Args[0]
 		src := v.Args[1]
 		mem := v.Args[2]
-		if !(size >= 32 && size <= 16*64 && size%16 == 0) {
+		if !(size >= 32 && size <= 16*64 && size%16 == 0 && !config.noDuffDevice) {
 			break
 		}
 		v.reset(OpAMD64DUFFCOPY)
@@ -8829,14 +8829,14 @@ func rewriteValueAMD64_OpMove(v *Value, config *Config) bool {
 		return true
 	}
 	// match: (Move [size] dst src mem)
-	// cond: size > 16*64 && size%8 == 0
+	// cond: (size > 16*64 || config.noDuffDevice) && size%8 == 0
 	// result: (REPMOVSQ dst src (MOVQconst [size/8]) mem)
 	for {
 		size := v.AuxInt
 		dst := v.Args[0]
 		src := v.Args[1]
 		mem := v.Args[2]
-		if !(size > 16*64 && size%8 == 0) {
+		if !((size > 16*64 || config.noDuffDevice) && size%8 == 0) {
 			break
 		}
 		v.reset(OpAMD64REPMOVSQ)
@@ -13693,13 +13693,13 @@ func rewriteValueAMD64_OpZero(v *Value, config *Config) bool {
 		return true
 	}
 	// match: (Zero [size] destptr mem)
-	// cond: size <= 1024 && size%8 == 0 && size%16 != 0
+	// cond: size <= 1024 && size%8 == 0 && size%16 != 0 && !config.noDuffDevice
 	// result: (Zero [size-8] (ADDQconst [8] destptr) (MOVQstore destptr (MOVQconst [0]) mem))
 	for {
 		size := v.AuxInt
 		destptr := v.Args[0]
 		mem := v.Args[1]
-		if !(size <= 1024 && size%8 == 0 && size%16 != 0) {
+		if !(size <= 1024 && size%8 == 0 && size%16 != 0 && !config.noDuffDevice) {
 			break
 		}
 		v.reset(OpZero)
@@ -13718,13 +13718,13 @@ func rewriteValueAMD64_OpZero(v *Value, config *Config) bool {
 		return true
 	}
 	// match: (Zero [size] destptr mem)
-	// cond: size <= 1024 && size%16 == 0
+	// cond: size <= 1024 && size%16 == 0 && !config.noDuffDevice
 	// result: (DUFFZERO [duffStart(size)] (ADDQconst [duffAdj(size)] destptr) (MOVOconst [0]) mem)
 	for {
 		size := v.AuxInt
 		destptr := v.Args[0]
 		mem := v.Args[1]
-		if !(size <= 1024 && size%16 == 0) {
+		if !(size <= 1024 && size%16 == 0 && !config.noDuffDevice) {
 			break
 		}
 		v.reset(OpAMD64DUFFZERO)
@@ -13740,13 +13740,13 @@ func rewriteValueAMD64_OpZero(v *Value, config *Config) bool {
 		return true
 	}
 	// match: (Zero [size] destptr mem)
-	// cond: size > 1024 && size%8 == 0
+	// cond: (size > 1024 || (config.noDuffDevice && size > 32)) && size%8 == 0
 	// result: (REPSTOSQ destptr (MOVQconst [size/8]) (MOVQconst [0]) mem)
 	for {
 		size := v.AuxInt
 		destptr := v.Args[0]
 		mem := v.Args[1]
-		if !(size > 1024 && size%8 == 0) {
+		if !((size > 1024 || (config.noDuffDevice && size > 32)) && size%8 == 0) {
 			break
 		}
 		v.reset(OpAMD64REPSTOSQ)