diff --git a/llvm/include/llvm/IR/PatternMatch.h b/llvm/include/llvm/IR/PatternMatch.h
--- a/llvm/include/llvm/IR/PatternMatch.h
+++ b/llvm/include/llvm/IR/PatternMatch.h
@@ -262,18 +262,23 @@
   return constantint_match<Val>();
 }
 
-/// This helper class is used to match scalar and fixed width vector integer
-/// constants that satisfy a specified predicate.
-/// For vector constants, undefined elements are ignored.
+/// This helper class is used to match integer constant scalars, vector splats,
+/// and fixed width vectors that satisfy a specified predicate.
+/// For fixed width vector constants, undefined elements are ignored.
 template <typename Predicate> struct cst_pred_ty : public Predicate {
   template <typename ITy> bool match(ITy *V) {
     if (const auto *CI = dyn_cast<ConstantInt>(V))
       return this->isValue(CI->getValue());
-    if (const auto *FVTy = dyn_cast<FixedVectorType>(V->getType())) {
+    if (const auto *VTy = dyn_cast<VectorType>(V->getType())) {
       if (const auto *C = dyn_cast<Constant>(V)) {
         if (const auto *CI = dyn_cast_or_null<ConstantInt>(C->getSplatValue()))
           return this->isValue(CI->getValue());
 
+        // Number of elements of a scalable vector unknown at compile time
+        auto *FVTy = dyn_cast<FixedVectorType>(VTy);
+        if (!FVTy)
+          return false;
+
         // Non-splat vector constant: check each element for a match.
         unsigned NumElts = FVTy->getNumElements();
         assert(NumElts != 0 && "Constant vector with no elements?");
@@ -321,25 +326,25 @@
   }
 };
 
-/// This helper class is used to match scalar and vector floating-point
-/// constants that satisfy a specified predicate.
-/// For vector constants, undefined elements are ignored.
+/// This helper class is used to match float constant scalars, vector splats,
+/// and fixed width vectors that satisfy a specified predicate.
+/// For fixed width vector constants, undefined elements are ignored.
 template <typename Predicate> struct cstfp_pred_ty : public Predicate {
   template <typename ITy> bool match(ITy *V) {
     if (const auto *CF = dyn_cast<ConstantFP>(V))
       return this->isValue(CF->getValueAPF());
-    if (V->getType()->isVectorTy()) {
+    if (const auto *VTy = dyn_cast<VectorType>(V->getType())) {
       if (const auto *C = dyn_cast<Constant>(V)) {
         if (const auto *CF = dyn_cast_or_null<ConstantFP>(C->getSplatValue()))
           return this->isValue(CF->getValueAPF());
 
         // Number of elements of a scalable vector unknown at compile time
-        if (isa<ScalableVectorType>(V->getType()))
+        auto *FVTy = dyn_cast<FixedVectorType>(VTy);
+        if (!FVTy)
           return false;
 
         // Non-splat vector constant: check each element for a match.
-        unsigned NumElts =
-            cast<FixedVectorType>(V->getType())->getNumElements();
+        unsigned NumElts = FVTy->getNumElements();
         assert(NumElts != 0 && "Constant vector with no elements?");
         bool HasNonUndefElements = false;
         for (unsigned i = 0; i != NumElts; ++i) {
diff --git a/llvm/test/Transforms/InstCombine/fmul.ll b/llvm/test/Transforms/InstCombine/fmul.ll
--- a/llvm/test/Transforms/InstCombine/fmul.ll
+++ b/llvm/test/Transforms/InstCombine/fmul.ll
@@ -1164,3 +1164,12 @@
   %mul = fmul fast double %sqr, %sel
   ret double %mul
 }
+
+; fastmath => z * splat(0) = splat(0), even for scalable vectors
+define <vscale x 2 x float> @mul_scalable_splat_zero(<vscale x 2 x float> %z) {
+; CHECK-LABEL: @mul_scalable_splat_zero(
+; CHECK-NEXT:    ret <vscale x 2 x float> zeroinitializer
+  %shuf = shufflevector <vscale x 2 x float> insertelement (<vscale x 2 x float> undef, float 0.0, i32 0), <vscale x 2 x float> undef, <vscale x 2 x i32> zeroinitializer
+  %t3 = fmul fast <vscale x 2 x float> %shuf, %z
+  ret <vscale x 2 x float> %t3
+}
diff --git a/llvm/test/Transforms/InstCombine/mul.ll b/llvm/test/Transforms/InstCombine/mul.ll
--- a/llvm/test/Transforms/InstCombine/mul.ll
+++ b/llvm/test/Transforms/InstCombine/mul.ll
@@ -856,3 +856,12 @@
   %m = mul <4 x i32> %r, %r
   ret <4 x i32> %m
 }
+
+; z * splat(0) = splat(0), even for scalable vectors
+define <vscale x 2 x i64> @mul_scalable_splat_zero(<vscale x 2 x i64> %z) {
+; CHECK-LABEL: @mul_scalable_splat_zero(
+; CHECK-NEXT:    ret <vscale x 2 x i64> zeroinitializer
+  %shuf = shufflevector <vscale x 2 x i64> insertelement (<vscale x 2 x i64> undef, i64 0, i32 0), <vscale x 2 x i64> undef, <vscale x 2 x i32> zeroinitializer
+  %t3 = mul <vscale x 2 x i64> %shuf, %z
+  ret <vscale x 2 x i64> %t3
+}
diff --git a/llvm/unittests/IR/PatternMatch.cpp b/llvm/unittests/IR/PatternMatch.cpp
--- a/llvm/unittests/IR/PatternMatch.cpp
+++ b/llvm/unittests/IR/PatternMatch.cpp
@@ -1325,6 +1325,183 @@
                             m_SpecificInt(10))));
 }
 
+namespace {
+
+struct is_unsigned_zero_pred {
+  bool isValue(const APInt &C) { return C.isNullValue(); }
+};
+
+struct is_float_zero_pred {
+  bool isValue(const APFloat &C) { return C.isZero(); }
+};
+
+template <typename T> struct always_true_pred {
+  bool isValue(const T &) { return true; }
+};
+
+template <typename T> struct always_false_pred {
+  bool isValue(const T &) { return false; }
+};
+
+struct is_unsigned_max_pred {
+  bool isValue(const APInt &C) { return C.isMaxValue(); }
+};
+
+struct is_float_nan_pred {
+  bool isValue(const APFloat &C) { return C.isNaN(); }
+};
+
+} // namespace
+
+TEST_F(PatternMatchTest, ConstantPredicateType) {
+
+  // Scalar integer
+  APInt U32Max = APInt::getAllOnesValue(32);
+  APInt U32Zero = APInt::getNullValue(32);
+  APInt U32DeadBeef(32, 0xDEADBEEF);
+
+  Type *U32Ty = Type::getInt32Ty(Ctx);
+
+  Constant *CU32Max = Constant::getIntegerValue(U32Ty, U32Max);
+  Constant *CU32Zero = Constant::getIntegerValue(U32Ty, U32Zero);
+  Constant *CU32DeadBeef = Constant::getIntegerValue(U32Ty, U32DeadBeef);
+
+  EXPECT_TRUE(match(CU32Max, cst_pred_ty<is_unsigned_max_pred>()));
+  EXPECT_FALSE(match(CU32Max, cst_pred_ty<is_unsigned_zero_pred>()));
+  EXPECT_TRUE(match(CU32Max, cst_pred_ty<always_true_pred<APInt>>()));
+  EXPECT_FALSE(match(CU32Max, cst_pred_ty<always_false_pred<APInt>>()));
+
+  EXPECT_FALSE(match(CU32Zero, cst_pred_ty<is_unsigned_max_pred>()));
+  EXPECT_TRUE(match(CU32Zero, cst_pred_ty<is_unsigned_zero_pred>()));
+  EXPECT_TRUE(match(CU32Zero, cst_pred_ty<always_true_pred<APInt>>()));
+  EXPECT_FALSE(match(CU32Zero, cst_pred_ty<always_false_pred<APInt>>()));
+
+  EXPECT_FALSE(match(CU32DeadBeef, cst_pred_ty<is_unsigned_max_pred>()));
+  EXPECT_FALSE(match(CU32DeadBeef, cst_pred_ty<is_unsigned_zero_pred>()));
+  EXPECT_TRUE(match(CU32DeadBeef, cst_pred_ty<always_true_pred<APInt>>()));
+  EXPECT_FALSE(match(CU32DeadBeef, cst_pred_ty<always_false_pred<APInt>>()));
+
+  // Scalar float
+  APFloat F32NaN = APFloat::getNaN(APFloat::IEEEsingle());
+  APFloat F32Zero = APFloat::getZero(APFloat::IEEEsingle());
+  APFloat F32Pi(3.14f);
+
+  Type *F32Ty = Type::getFloatTy(Ctx);
+
+  Constant *CF32NaN = ConstantFP::get(F32Ty, F32NaN);
+  Constant *CF32Zero = ConstantFP::get(F32Ty, F32Zero);
+  Constant *CF32Pi = ConstantFP::get(F32Ty, F32Pi);
+
+  EXPECT_TRUE(match(CF32NaN, cstfp_pred_ty<is_float_nan_pred>()));
+  EXPECT_FALSE(match(CF32NaN, cstfp_pred_ty<is_float_zero_pred>()));
+  EXPECT_TRUE(match(CF32NaN, cstfp_pred_ty<always_true_pred<APFloat>>()));
+  EXPECT_FALSE(match(CF32NaN, cstfp_pred_ty<always_false_pred<APFloat>>()));
+
+  EXPECT_FALSE(match(CF32Zero, cstfp_pred_ty<is_float_nan_pred>()));
+  EXPECT_TRUE(match(CF32Zero, cstfp_pred_ty<is_float_zero_pred>()));
+  EXPECT_TRUE(match(CF32Zero, cstfp_pred_ty<always_true_pred<APFloat>>()));
+  EXPECT_FALSE(match(CF32Zero, cstfp_pred_ty<always_false_pred<APFloat>>()));
+
+  EXPECT_FALSE(match(CF32Pi, cstfp_pred_ty<is_float_nan_pred>()));
+  EXPECT_FALSE(match(CF32Pi, cstfp_pred_ty<is_float_zero_pred>()));
+  EXPECT_TRUE(match(CF32Pi, cstfp_pred_ty<always_true_pred<APFloat>>()));
+  EXPECT_FALSE(match(CF32Pi, cstfp_pred_ty<always_false_pred<APFloat>>()));
+
+  ElementCount FixedEC(4, false);
+  ElementCount ScalableEC(4, true);
+
+  // Vector splat
+
+  for (auto EC : {FixedEC, ScalableEC}) {
+    // integer
+
+    Constant *CSplatU32Max = ConstantVector::getSplat(EC, CU32Max);
+    Constant *CSplatU32Zero = ConstantVector::getSplat(EC, CU32Zero);
+    Constant *CSplatU32DeadBeef = ConstantVector::getSplat(EC, CU32DeadBeef);
+
+    EXPECT_TRUE(match(CSplatU32Max, cst_pred_ty<is_unsigned_max_pred>()));
+    EXPECT_FALSE(match(CSplatU32Max, cst_pred_ty<is_unsigned_zero_pred>()));
+    EXPECT_TRUE(match(CSplatU32Max, cst_pred_ty<always_true_pred<APInt>>()));
+    EXPECT_FALSE(match(CSplatU32Max, cst_pred_ty<always_false_pred<APInt>>()));
+
+    EXPECT_FALSE(match(CSplatU32Zero, cst_pred_ty<is_unsigned_max_pred>()));
+    EXPECT_TRUE(match(CSplatU32Zero, cst_pred_ty<is_unsigned_zero_pred>()));
+    EXPECT_TRUE(match(CSplatU32Zero, cst_pred_ty<always_true_pred<APInt>>()));
+    EXPECT_FALSE(match(CSplatU32Zero, cst_pred_ty<always_false_pred<APInt>>()));
+
+    EXPECT_FALSE(match(CSplatU32DeadBeef, cst_pred_ty<is_unsigned_max_pred>()));
+    EXPECT_FALSE(
+        match(CSplatU32DeadBeef, cst_pred_ty<is_unsigned_zero_pred>()));
+    EXPECT_TRUE(
+        match(CSplatU32DeadBeef, cst_pred_ty<always_true_pred<APInt>>()));
+    EXPECT_FALSE(
+        match(CSplatU32DeadBeef, cst_pred_ty<always_false_pred<APInt>>()));
+
+    // float
+
+    Constant *CSplatF32NaN = ConstantVector::getSplat(EC, CF32NaN);
+    Constant *CSplatF32Zero = ConstantVector::getSplat(EC, CF32Zero);
+    Constant *CSplatF32Pi = ConstantVector::getSplat(EC, CF32Pi);
+
+    EXPECT_TRUE(match(CSplatF32NaN, cstfp_pred_ty<is_float_nan_pred>()));
+    EXPECT_FALSE(match(CSplatF32NaN, cstfp_pred_ty<is_float_zero_pred>()));
+    EXPECT_TRUE(
+        match(CSplatF32NaN, cstfp_pred_ty<always_true_pred<APFloat>>()));
+    EXPECT_FALSE(
+        match(CSplatF32NaN, cstfp_pred_ty<always_false_pred<APFloat>>()));
+
+    EXPECT_FALSE(match(CSplatF32Zero, cstfp_pred_ty<is_float_nan_pred>()));
+    EXPECT_TRUE(match(CSplatF32Zero, cstfp_pred_ty<is_float_zero_pred>()));
+    EXPECT_TRUE(
+        match(CSplatF32Zero, cstfp_pred_ty<always_true_pred<APFloat>>()));
+    EXPECT_FALSE(
+        match(CSplatF32Zero, cstfp_pred_ty<always_false_pred<APFloat>>()));
+
+    EXPECT_FALSE(match(CSplatF32Pi, cstfp_pred_ty<is_float_nan_pred>()));
+    EXPECT_FALSE(match(CSplatF32Pi, cstfp_pred_ty<is_float_zero_pred>()));
+    EXPECT_TRUE(match(CSplatF32Pi, cstfp_pred_ty<always_true_pred<APFloat>>()));
+    EXPECT_FALSE(
+        match(CSplatF32Pi, cstfp_pred_ty<always_false_pred<APFloat>>()));
+  }
+
+  // Int arbitrary vector
+
+  Constant *CMixedU32 = ConstantVector::get({CU32Max, CU32Zero, CU32DeadBeef});
+  Constant *CU32Undef = UndefValue::get(U32Ty);
+  Constant *CU32MaxWithUndef =
+      ConstantVector::get({CU32Undef, CU32Max, CU32Undef});
+
+  EXPECT_FALSE(match(CMixedU32, cst_pred_ty<is_unsigned_max_pred>()));
+  EXPECT_FALSE(match(CMixedU32, cst_pred_ty<is_unsigned_zero_pred>()));
+  EXPECT_TRUE(match(CMixedU32, cst_pred_ty<always_true_pred<APInt>>()));
+  EXPECT_FALSE(match(CMixedU32, cst_pred_ty<always_false_pred<APInt>>()));
+
+  EXPECT_TRUE(match(CU32MaxWithUndef, cst_pred_ty<is_unsigned_max_pred>()));
+  EXPECT_FALSE(match(CU32MaxWithUndef, cst_pred_ty<is_unsigned_zero_pred>()));
+  EXPECT_TRUE(match(CU32MaxWithUndef, cst_pred_ty<always_true_pred<APInt>>()));
+  EXPECT_FALSE(
+      match(CU32MaxWithUndef, cst_pred_ty<always_false_pred<APInt>>()));
+
+  // Float arbitrary vector
+
+  Constant *CMixedF32 = ConstantVector::get({CF32NaN, CF32Zero, CF32Pi});
+  Constant *CF32Undef = UndefValue::get(F32Ty);
+  Constant *CF32NaNWithUndef =
+      ConstantVector::get({CF32Undef, CF32NaN, CF32Undef});
+
+  EXPECT_FALSE(match(CMixedF32, cstfp_pred_ty<is_float_nan_pred>()));
+  EXPECT_FALSE(match(CMixedF32, cstfp_pred_ty<is_float_zero_pred>()));
+  EXPECT_TRUE(match(CMixedF32, cstfp_pred_ty<always_true_pred<APFloat>>()));
+  EXPECT_FALSE(match(CMixedF32, cstfp_pred_ty<always_false_pred<APFloat>>()));
+
+  EXPECT_TRUE(match(CF32NaNWithUndef, cstfp_pred_ty<is_float_nan_pred>()));
+  EXPECT_FALSE(match(CF32NaNWithUndef, cstfp_pred_ty<is_float_zero_pred>()));
+  EXPECT_TRUE(
+      match(CF32NaNWithUndef, cstfp_pred_ty<always_true_pred<APFloat>>()));
+  EXPECT_FALSE(
+      match(CF32NaNWithUndef, cstfp_pred_ty<always_false_pred<APFloat>>()));
+}
+
 template <typename T> struct MutableConstTest : PatternMatchTest { };
 
 typedef ::testing::Types<std::tuple<Value*, Instruction*>,