Index: lib/Target/SystemZ/SystemZISelLowering.h
===================================================================
--- lib/Target/SystemZ/SystemZISelLowering.h
+++ lib/Target/SystemZ/SystemZISelLowering.h
@@ -516,6 +516,7 @@
   static bool tryBuildVectorByteMask(BuildVectorSDNode *BVN, uint64_t &Mask);
   static bool analyzeFPImm(const APFloat &Imm, unsigned BitWidth,
                  unsigned &Start, unsigned &End, const SystemZInstrInfo *TII);
+  bool isBuildVectorAllLegalFPImms(BuildVectorSDNode *BVN) const;
 private:
   const SystemZSubtarget &Subtarget;
 
Index: lib/Target/SystemZ/SystemZISelLowering.cpp
===================================================================
--- lib/Target/SystemZ/SystemZISelLowering.cpp
+++ lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -4559,6 +4559,24 @@
   return Result;
 }
 
+bool SystemZTargetLowering::
+isBuildVectorAllLegalFPImms(BuildVectorSDNode *BVN) const {
+  EVT VT = BVN->getValueType(0);
+  unsigned NumElements = VT.getVectorNumElements();
+  EVT EltVT = VT.getScalarType();
+  if (!EltVT.isFloatingPoint())
+    return false;
+  for (unsigned I = 0; I < NumElements; ++I) {
+    SDValue Op = BVN->getOperand(I);
+    if (Op.isUndef())
+      continue;
+    ConstantFPSDNode *FPImm = dyn_cast<ConstantFPSDNode>(Op);
+    if (FPImm == nullptr || !isFPImmLegal(FPImm->getValueAPF(), EltVT))
+      return false;
+  }
+  return true;
+}
+
 SDValue SystemZTargetLowering::lowerBUILD_VECTOR(SDValue Op,
                                                  SelectionDAG &DAG) const {
   const SystemZInstrInfo *TII =
@@ -4574,7 +4592,8 @@
     uint64_t Mask;
     if (ISD::isBuildVectorAllZeros(Op.getNode()) ||
         ISD::isBuildVectorAllOnes(Op.getNode()) ||
-        (VT.isInteger() && tryBuildVectorByteMask(BVN, Mask)))
+        (tryBuildVectorByteMask(BVN, Mask) &&
+         (VT.isInteger() || isBuildVectorAllLegalFPImms(BVN))))
       return Op;
 
     // Try using some form of replication.
Index: test/CodeGen/SystemZ/vec-const-05.ll
===================================================================
--- test/CodeGen/SystemZ/vec-const-05.ll
+++ test/CodeGen/SystemZ/vec-const-05.ll
@@ -1,28 +1,63 @@
-; Test vector byte masks, v4f32 version. Only all-zero vectors are handled.
+; Test vector byte masks, v4f32 version.
 ;
 ; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z13 | FileCheck %s
 
 ; Test an all-zeros vector.
-define <4 x float> @f0() {
-; CHECK-LABEL: f0:
+define <4 x float> @f1() {
+; CHECK-LABEL: f1:
 ; CHECK: vgbm %v24, 0
 ; CHECK: br %r14
   ret <4 x float> zeroinitializer
 }
 
-; Test that undefs are treated as zero.
-define <4 x float> @f1() {
-; CHECK-LABEL: f1:
-; CHECK: vgbm %v24, 0
+; Test an all-ones vector.
+define <4 x float> @f2() {
+; CHECK-LABEL: f2:
+; CHECK: vgbm %v24, 65535
 ; CHECK: br %r14
-  ret <4 x float> <float zeroinitializer, float undef,
-                   float zeroinitializer, float undef>
+  ret <4 x float> <float 0xffffffffe0000000, float 0xffffffffe0000000,
+                   float 0xffffffffe0000000, float 0xffffffffe0000000>
+}
+
+; Test a mixed vector (mask 0xc731).
+define <4 x float> @f3() {
+; CHECK-LABEL: f3:
+; CHECK: vgbm %v24, 50993
+; CHECK: br %r14
+  ret <4 x float> <float 0xffffe00000000000, float 0x381fffffe0000000,
+                   float 0x379fffe000000000, float 0x371fe00000000000>
+}
+
+; Test that undefs are treated as zero (mask 0xc031).
+define <4 x float> @f4() {
+; CHECK-LABEL: f4:
+; CHECK: vgbm %v24, 49201
+; CHECK: br %r14
+  ret <4 x float> <float 0xffffe00000000000, float undef,
+                   float 0x379fffe000000000, float 0x371fe00000000000>
+}
+
+; Test that we don't use VGBM if one of the bytes is not 0 or 0xff.
+define <4 x float> @f5() {
+; CHECK-LABEL: f5:
+; CHECK-NOT: vgbm
+; CHECK: br %r14
+  ret <4 x float> <float 0xffffe00000000000, float 0x381fffffc0000000,
+                   float 0x379fffe000000000, float 0x371fe00000000000>
 }
 
 ; Test an all-zeros v2f32 that gets promoted to v4f32.
-define <2 x float> @f2() {
-; CHECK-LABEL: f2:
+define <2 x float> @f6() {
+; CHECK-LABEL: f6:
 ; CHECK: vgbm %v24, 0
 ; CHECK: br %r14
   ret <2 x float> zeroinitializer
 }
+
+; Test a mixed v2f32 that gets promoted to v4f32 (mask 0xc700).
+define <2 x float> @f7() {
+; CHECK-LABEL: f7:
+; CHECK: vgbm %v24, 50944
+; CHECK: br %r14
+  ret <2 x float> <float 0xffffe00000000000, float 0x381fffffe0000000>
+}
Index: test/CodeGen/SystemZ/vec-const-06.ll
===================================================================
--- test/CodeGen/SystemZ/vec-const-06.ll
+++ test/CodeGen/SystemZ/vec-const-06.ll
@@ -1,19 +1,35 @@
-; Test vector byte masks, v2f64 version. Only all-zero vectors are handled.
+; Test vector byte masks, v2f64 version.
 ;
 ; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z13 | FileCheck %s
 
 ; Test an all-zeros vector.
-define <2 x double> @f0() {
-; CHECK-LABEL: f0:
+define <2 x double> @f1() {
+; CHECK-LABEL: f1:
 ; CHECK: vgbm %v24, 0
 ; CHECK: br %r14
   ret <2 x double> zeroinitializer
 }
 
+; Test an all-ones vector.
+define <2 x double> @f2() {
+; CHECK-LABEL: f2:
+; CHECK: vgbm %v24, 65535
+; CHECK: br %r14
+  ret <2 x double> <double 0xffffffffffffffff, double 0xffffffffffffffff>
+}
+
 ; Test that undefs are treated as zero.
-define <2 x double> @f1() {
-; CHECK-LABEL: f1:
-; CHECK: vgbm %v24, 0
+define <2 x double> @f3() {
+; CHECK-LABEL: f3:
+; CHECK: vgbm %v24, 65280
+; CHECK: br %r14
+  ret <2 x double> <double 0xffffffffffffffff, double undef>
+}
+
+; Test that we don't use VGBM if one of the bytes is not 0 or 0xff.
+define <2 x double> @f4() {
+; CHECK-LABEL: f4:
+; CHECK-NOT: vgbm
 ; CHECK: br %r14
-  ret <2 x double> <double zeroinitializer, double undef>
+  ret <2 x double> <double 0xfe000000ffff0000, double 0x00ffffff00ffff00>
 }