diff --git a/src/cmd/compile/internal/gc/asm_test.go b/src/cmd/compile/internal/gc/asm_test.go
index 906e118..97d5b7f 100644
--- a/src/cmd/compile/internal/gc/asm_test.go
+++ b/src/cmd/compile/internal/gc/asm_test.go
@@ -1457,6 +1457,39 @@
 		`,
 		pos: []string{"\tFLOGR\t"},
 	},
+	// Intrinsic tests for math.
+	{
+		fn: `
+		func ceil(x float64) float64 {
+			return math.Ceil(x)
+		}
+		`,
+		pos: []string{"\tFIDBR\t[$]6"},
+	},
+	{
+		fn: `
+		func floor(x float64) float64 {
+			return math.Floor(x)
+		}
+		`,
+		pos: []string{"\tFIDBR\t[$]7"},
+	},
+	{
+		fn: `
+		func round(x float64) float64 {
+			return math.Round(x)
+		}
+		`,
+		pos: []string{"\tFIDBR\t[$]1"},
+	},
+	{
+		fn: `
+		func trunc(x float64) float64 {
+			return math.Trunc(x)
+		}
+		`,
+		pos: []string{"\tFIDBR\t[$]5"},
+	},
 	{
 		// check that stack store is optimized away
 		fn: `
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 04f1a92..94446d8 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -2734,17 +2734,22 @@
 		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpTrunc, types.Types[TFLOAT64], args[0])
 		},
-		sys.PPC64)
+		sys.PPC64, sys.S390X)
 	addF("math", "Ceil",
 		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpCeil, types.Types[TFLOAT64], args[0])
 		},
-		sys.PPC64)
+		sys.PPC64, sys.S390X)
 	addF("math", "Floor",
 		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpFloor, types.Types[TFLOAT64], args[0])
 		},
-		sys.PPC64)
+		sys.PPC64, sys.S390X)
+	addF("math", "Round",
+		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
+			return s.newValue1(ssa.OpRound, types.Types[TFLOAT64], args[0])
+		},
+		sys.S390X)
 
 	/******** math/bits ********/
 	addF("math/bits", "TrailingZeros64",
diff --git a/src/cmd/compile/internal/s390x/ssa.go b/src/cmd/compile/internal/s390x/ssa.go
index 6e63748..19899ec 100644
--- a/src/cmd/compile/internal/s390x/ssa.go
+++ b/src/cmd/compile/internal/s390x/ssa.go
@@ -207,6 +207,13 @@
 		p.Reg = r2
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = r
+	case ssa.OpS390XFIDBR:
+		switch v.AuxInt {
+		case 0, 1, 3, 4, 5, 6, 7:
+			opregregimm(s, v.Op.Asm(), v.Reg(), v.Args[0].Reg(), v.AuxInt)
+		default:
+			v.Fatalf("invalid FIDBR mask: %v", v.AuxInt)
+		}
 	case ssa.OpS390XDIVD, ssa.OpS390XDIVW,
 		ssa.OpS390XDIVDU, ssa.OpS390XDIVWU,
 		ssa.OpS390XMODD, ssa.OpS390XMODW,
diff --git a/src/cmd/compile/internal/ssa/gen/S390X.rules b/src/cmd/compile/internal/ssa/gen/S390X.rules
index 8a627e7..d03ca32 100644
--- a/src/cmd/compile/internal/ssa/gen/S390X.rules
+++ b/src/cmd/compile/internal/ssa/gen/S390X.rules
@@ -107,7 +107,12 @@
 (Bswap64 x) -> (MOVDBR x)
 (Bswap32 x) -> (MOVWBR x)
 
-(Sqrt x) -> (FSQRT x)
+// math package intrinsics
+(Sqrt  x) -> (FSQRT x)
+(Floor x) -> (FIDBR [7] x)
+(Ceil  x) -> (FIDBR [6] x)
+(Trunc x) -> (FIDBR [5] x)
+(Round x) -> (FIDBR [1] x)
 
 // Atomic loads.
 (AtomicLoad32 ptr mem) -> (MOVWZatomicload ptr mem)
diff --git a/src/cmd/compile/internal/ssa/gen/S390XOps.go b/src/cmd/compile/internal/ssa/gen/S390XOps.go
index 2a08a27..b330398 100644
--- a/src/cmd/compile/internal/ssa/gen/S390XOps.go
+++ b/src/cmd/compile/internal/ssa/gen/S390XOps.go
@@ -206,6 +206,17 @@
 		{name: "FMSUBS", argLength: 3, reg: fp31, asm: "FMSUBS", resultInArg0: true},                                             // fp32 arg1 * arg2 - arg0
 		{name: "FMSUB", argLength: 3, reg: fp31, asm: "FMSUB", resultInArg0: true},                                               // fp64 arg1 * arg2 - arg0
 
+		// Round to integer, float64 only.
+		//
+		// aux | rounding mode
+		// ----+-----------------------------------
+		//   1 | round to nearest, ties away from 0
+		//   4 | round to nearest, ties to even
+		//   5 | round toward 0
+		//   6 | round toward +∞
+		//   7 | round toward -∞
+		{name: "FIDBR", argLength: 1, reg: fp11, asm: "FIDBR", aux: "Int8"},
+
 		{name: "FMOVSload", argLength: 2, reg: fpload, asm: "FMOVS", aux: "SymOff", faultOnNilArg0: true, symEffect: "Read"}, // fp32 load
 		{name: "FMOVDload", argLength: 2, reg: fpload, asm: "FMOVD", aux: "SymOff", faultOnNilArg0: true, symEffect: "Read"}, // fp64 load
 		{name: "FMOVSconst", reg: fp01, asm: "FMOVS", aux: "Float32", rematerializeable: true},                               // fp32 constant
diff --git a/src/cmd/compile/internal/ssa/gen/genericOps.go b/src/cmd/compile/internal/ssa/gen/genericOps.go
index 6f8d10a..2967d29 100644
--- a/src/cmd/compile/internal/ssa/gen/genericOps.go
+++ b/src/cmd/compile/internal/ssa/gen/genericOps.go
@@ -255,10 +255,23 @@
 	{name: "PopCount32", argLength: 1}, // Count bits in arg[0]
 	{name: "PopCount64", argLength: 1}, // Count bits in arg[0]
 
-	{name: "Sqrt", argLength: 1},  // sqrt(arg0), float64 only
-	{name: "Floor", argLength: 1}, // floor(arg0), float64 only
-	{name: "Ceil", argLength: 1},  // ceil(arg0), float64 only
-	{name: "Trunc", argLength: 1}, // trunc(arg0), float64 only
+	// Square root, float64 only.
+	// Special cases:
+	//   +∞  → +∞
+	//   ±0  → ±0 (sign preserved)
+	//   x<0 → NaN
+	//   NaN → NaN
+	{name: "Sqrt", argLength: 1}, // √arg0
+
+	// Round to integer, float64 only.
+	// Special cases:
+	//   ±∞  → ±∞ (sign preserved)
+	//   ±0  → ±0 (sign preserved)
+	//   NaN → NaN
+	{name: "Floor", argLength: 1}, // round arg0 toward -∞
+	{name: "Ceil", argLength: 1},  // round arg0 toward +∞
+	{name: "Trunc", argLength: 1}, // round arg0 toward 0
+	{name: "Round", argLength: 1}, // round arg0 to nearest, ties away from 0
 
 	// Data movement, max argument length for Phi is indefinite so just pick
 	// a really large number
diff --git a/src/cmd/compile/internal/ssa/opGen.go b/src/cmd/compile/internal/ssa/opGen.go
index c99733e..6cac15a 100644
--- a/src/cmd/compile/internal/ssa/opGen.go
+++ b/src/cmd/compile/internal/ssa/opGen.go
@@ -1448,6 +1448,7 @@
 	OpS390XFMADD
 	OpS390XFMSUBS
 	OpS390XFMSUB
+	OpS390XFIDBR
 	OpS390XFMOVSload
 	OpS390XFMOVDload
 	OpS390XFMOVSconst
@@ -1836,6 +1837,7 @@
 	OpFloor
 	OpCeil
 	OpTrunc
+	OpRound
 	OpPhi
 	OpCopy
 	OpConvert
@@ -18603,6 +18605,20 @@
 		},
 	},
 	{
+		name:    "FIDBR",
+		auxType: auxInt8,
+		argLen:  1,
+		asm:     s390x.AFIDBR,
+		reg: regInfo{
+			inputs: []inputInfo{
+				{0, 4294901760}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15
+			},
+			outputs: []outputInfo{
+				{0, 4294901760}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15
+			},
+		},
+	},
+	{
 		name:           "FMOVSload",
 		auxType:        auxSymOff,
 		argLen:         2,
@@ -22438,6 +22454,11 @@
 		generic: true,
 	},
 	{
+		name:    "Round",
+		argLen:  1,
+		generic: true,
+	},
+	{
 		name:    "Phi",
 		argLen:  -1,
 		generic: true,
diff --git a/src/cmd/compile/internal/ssa/rewriteS390X.go b/src/cmd/compile/internal/ssa/rewriteS390X.go
index 8ff1f25..7875898 100644
--- a/src/cmd/compile/internal/ssa/rewriteS390X.go
+++ b/src/cmd/compile/internal/ssa/rewriteS390X.go
@@ -73,6 +73,8 @@
 		return rewriteValueS390X_OpBswap32_0(v)
 	case OpBswap64:
 		return rewriteValueS390X_OpBswap64_0(v)
+	case OpCeil:
+		return rewriteValueS390X_OpCeil_0(v)
 	case OpClosureCall:
 		return rewriteValueS390X_OpClosureCall_0(v)
 	case OpCom16:
@@ -161,6 +163,8 @@
 		return rewriteValueS390X_OpEqB_0(v)
 	case OpEqPtr:
 		return rewriteValueS390X_OpEqPtr_0(v)
+	case OpFloor:
+		return rewriteValueS390X_OpFloor_0(v)
 	case OpGeq16:
 		return rewriteValueS390X_OpGeq16_0(v)
 	case OpGeq16U:
@@ -371,6 +375,8 @@
 		return rewriteValueS390X_OpOr8_0(v)
 	case OpOrB:
 		return rewriteValueS390X_OpOrB_0(v)
+	case OpRound:
+		return rewriteValueS390X_OpRound_0(v)
 	case OpRound32F:
 		return rewriteValueS390X_OpRound32F_0(v)
 	case OpRound64F:
@@ -685,6 +691,8 @@
 		return rewriteValueS390X_OpSub8_0(v)
 	case OpSubPtr:
 		return rewriteValueS390X_OpSubPtr_0(v)
+	case OpTrunc:
+		return rewriteValueS390X_OpTrunc_0(v)
 	case OpTrunc16to8:
 		return rewriteValueS390X_OpTrunc16to8_0(v)
 	case OpTrunc32to16:
@@ -1172,6 +1180,18 @@
 		return true
 	}
 }
+func rewriteValueS390X_OpCeil_0(v *Value) bool {
+	// match: (Ceil x)
+	// cond:
+	// result: (FIDBR [6] x)
+	for {
+		x := v.Args[0]
+		v.reset(OpS390XFIDBR)
+		v.AuxInt = 6
+		v.AddArg(x)
+		return true
+	}
+}
 func rewriteValueS390X_OpClosureCall_0(v *Value) bool {
 	// match: (ClosureCall [argwid] entry closure mem)
 	// cond:
@@ -1911,6 +1931,18 @@
 		return true
 	}
 }
+func rewriteValueS390X_OpFloor_0(v *Value) bool {
+	// match: (Floor x)
+	// cond:
+	// result: (FIDBR [7] x)
+	for {
+		x := v.Args[0]
+		v.reset(OpS390XFIDBR)
+		v.AuxInt = 7
+		v.AddArg(x)
+		return true
+	}
+}
 func rewriteValueS390X_OpGeq16_0(v *Value) bool {
 	b := v.Block
 	_ = b
@@ -4913,6 +4945,18 @@
 		return true
 	}
 }
+func rewriteValueS390X_OpRound_0(v *Value) bool {
+	// match: (Round x)
+	// cond:
+	// result: (FIDBR [1] x)
+	for {
+		x := v.Args[0]
+		v.reset(OpS390XFIDBR)
+		v.AuxInt = 1
+		v.AddArg(x)
+		return true
+	}
+}
 func rewriteValueS390X_OpRound32F_0(v *Value) bool {
 	// match: (Round32F x)
 	// cond:
@@ -36200,6 +36244,18 @@
 		return true
 	}
 }
+func rewriteValueS390X_OpTrunc_0(v *Value) bool {
+	// match: (Trunc x)
+	// cond:
+	// result: (FIDBR [5] x)
+	for {
+		x := v.Args[0]
+		v.reset(OpS390XFIDBR)
+		v.AuxInt = 5
+		v.AddArg(x)
+		return true
+	}
+}
 func rewriteValueS390X_OpTrunc16to8_0(v *Value) bool {
 	// match: (Trunc16to8 x)
 	// cond: